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KSEEB Class 10 SSLC Biology Chapter 4 Heredity And Evolution

A recognisable feature of a human being (or any other organism) like height, complexion, shape of hair, colour of eyes, and shape of nose and chin, etc, are called ‘characters’ or ‘traits’. The transmission of characters (or traits) from the parents to their offsprings is called heredity. In most simple terms, heredity means continuity of features from one generation to the next.

Two parents, a male and a female, are involved in sexual reproduction. The sexually reproducing organisms produce sex cells or gametes. The male gamete called sperm fuses with a female gamete called ovum (or egg) to form a zygote which gradually develops into a young one (or offspring), showing some

similarities with the parents. Actually, the hereditary information is present in the sex cells (or gametes) of the parents. Thus, gametes constitute the link between one generation and the next, and pass on the paternal (father’s) and maternal (mother’s) characters or traits to the offspring. This relation that continues to exist between successive generations is referred to as heredity.

Variations Although the offsprings inherit the characters (or traits) of the parents and resemble them very closelybut the resemblance is not complete in all respects. The offsprings are never a true copy of the parents. In fact, no two individuals are exactly alike and the members of any one species differ from one another in some characters (or traits) or the other. These differences are known as variations. So, from the biological point of view, variation is the occurrence of differences among the individuals of a species.

KSEEB Class 10 SSLC Biology Chapter 4 Heredity and Evolution

For example, people have different heights. Their complexion, type of hair, colour of eyes, shape of nose and shape of chin also show differences. The differences in the characters (or traits) among the individuals of a species is called variation. For example, human height a trait which shows variation. This is because some people are very tall, some are less tall, some have medium height, some have short height whereas others are very short.

Here is another example of variations in human beings which involves our ears. The lowest part of our ear is called earlobe. In most of the people, the earlobe is ‘hanging’ and it is called free earlobe In some people, however, the earlobe is closely attached to the side of the head and it is called attached earlobe.

Thus, most people have free earlobes whereas some people have attached earlobes. So, the free earlobes and attached earlobes are the two variations found in human population. Some amount of variations is produced even during asexual reproduction but it is very small. The number of variations produced during sexual reproduction .

however, very large. For example, the sugar cane plants reproduce by the process of asexual reproduction, so if we observe a field of sugar cane, we will find very little variations in various sugar cane plants. All the sugar cane plants almost look alike. But in animals (including human beings) which reproduce by the process of sexual reproduction, a large number of variations are produced. It is due to these variations that no two human beings look alike (except identical twins).

From this discussion we conclude that the number of successful variations is maximised by the process of sexual reproduction.  The reproduction of organisms produces variations. The variations produced in organisms during successive generations get accumulated in the organisms. The significance of a variation shows up only if it continues to be inherited by the offspring for several generations. This will become clear from the following example.

Suppose a bacterium produces two bacteria by asexual reproduction. Again suppose that one of the offspring bacterium has a variation due to which it can tolerate a little higher temperature (or little more heat) than the other one. Now, this variation of little more heat resistance will go on accumulating in the offsprings of successive generations of this bacterium. And this will ultimately give rise to a variant of bacteria which will be highly heat resistant and able to survive even at very high temperatures.

The great advantage of variation to a species is that it increases the chances of its survival in a changing environment. For example, the accumulation of ‘heat resistant’ variation (or trait) in some bacteria will ensure its survival even when the temperature in its environment rises too much due to a heat wave or some other reasons. On the other hand, the bacteria which did not have this variation to withstand heat would not survive under these circumstances and die.

KSEEB Class 10 SSLC Biology Chapter 4 Heredity and Evolution

Before we describe Mendel’s experiments for explaining the transmission of characteristics (or traits) from parents to their offsprings or progeny, we should know the meaning of some terms such as chromosome, gene, dominant gene, recessive gene, genotype, phenotype, F₁ generation and F₂ generation. These are described on the next page. Chromosome is a thread-like structure in the nucleus of a cell formed of DNA which carries the genes.

Different organisms have different number of chromosomes in their nuclei. A gene is a unit of DNA on a chromosome which governs the synthesis of one protein that controls a specific characteristic (or trait) of an organism). There are thousands of genes on a chromosome which control various characteristics of an organism. Genes are actually units of heredity which transfer characteristics (or traits) from parents to their offsprings during reproduction. Genes work in pairs.

In diagrams and in explanations of heredity, genes are represented by letters. Genes controlling the same characteristics are given the same letters. For example, the gene for tallness is represented by the letter T whereas the gene for dwarfness is represented by the letter t. The letters T and t actually represent two forms of the same gene (which controls the length of an organism, say the length of stem of a plant).

Please note that genes had not been discovered at the time when Mendel conducted his experiments on pea plants to study the inheritance of characteristics. The term ‘factors’ which were used by Mendel as carriers of heredity information are now known as ‘genes’.

Genes for controlling the same characteristic of an organism can be of two types : dominant or recessive. The gene which decides the appearance of an organism even in the presence of an alternative gene is known as a dominant gene. It dominates the recessive gene for the same characteristic on the other chromosome of the pair. The gene which can decide the appearance of an organism only in the presence of another identical gene is called a recessive gene.

A single recessive gene cannot decide the appearance of an organism. The dominant gene is represented by a capital letter and the corresponding recessive gene is represented by the corresponding small letter. For example, in pea plants, the dominant gene for tallness is T and the recessive gene for dwartfness is it.

Thus, when we write the genetic cross for pea plant, then the capital ‘T’ represents ‘tall’ and small ‘t’ represents ‘dwarf’. Genotype shows the genetic constitution of an organism. In simple words, genotype is the description of genes present in an organism. Genotype is always a pair of letters such as TT, Tt or tt (where T and t are the different forms of the same gene). Thus, the genotype of a tall plant could be TT or Tt whereas that of a dwarf plant is tt.

The characteristic (or trait) which is visible in an organism is called its phenotype. For example, being ‘tall’ or ‘dwarf’ (short) are phenotypes of a plant because these traits can be seen by us or they are visible to us. The phenotype of an organism is actually its physical characteristic which is determined by its genotype. For example, genotype TT or Tt results in a tall phenotype and the genotype tt results in a dwarf phenotype.

When two parents cross (or breed) to produce progeny (or offsprings), then their progeny is called first filial generation or F₁ generation (where F stands for Filial which denotes progeny of a cross).

When the first generation progeny cross (or breed) among themselves to produce second generation progeny, then this progeny is called second filial generation or F₂2 generation. In other words, the generation produced by crossing two F₁ progeny is called F₂ generation. An example will make it more clear. Mother and father are parental generation. Their children are F₁ generation, and the grandchildren are F₂ generation.

Gregor Mendel was the first scientist to make a systematic study of patterns of inheritance which involved the transfer of characteristics from parents to progeny. He did this by using different varieties of  pea plants (Pisum sativum) which he grew in his garden. Some of the characteristics (or traits) of the pea plants whose transmission to progeny was investigated by Mendel were height of pea plant or length of stem of pea plant (tall or dwarf), shape of seeds (round or wrinkled) and colour of seeds (yellow or green) .

A yet another contrasting characteristics (or traits) investigated were colours of flowers (white or violet). Mendel chose pea plants for studying inheritance because pea plants had a number of clear cut differences which were easy to tell apart. For example, some pea plants were ‘tall’ (having long stem) whereas others were ‘dwarf’ (having short stem). Some pea plants produced round-yellow seeds whereas others produced wrinkled-green seeds, etc.

Another reason for choosing pea plants was that they were self pollinating (which enabled them to produce next generation of plants easily). And finally, Mendel chose peaplants to study inheritance (and not animals including human beings) because many generations of pea plants can be produced in a comparatively short time span and their study is much simpler than that of animals. A new form of plant resulting from a cross (or breeding) of different varieties of a plant is known as a hybrid.

When we breed two pea plants having one contrasting characteristic each (or one trait each) to obtain new plants, then it is called a monohybrid cross. In monohybrid cross we will study the inheritance of one pair of contrasting characteristics ‘tallness’ and ‘dwarfness’ of the pea plants by their first generation and second generation progeny.

On the other hand, if we breed two pea plants having two contrasting characteristics each (or two traits each) to obtain new plants, then it is called a dihybrid cross. In the dihybrid cross we will study the inheritance of two pairs of contrasting characteristics of pea plants such as round-yellow seeds and wrinkled-green seeds.

KSEEB Class 10 SSLC Biology Chapter 4 Heredity and Evolution

Rules For The Inheritance of Traits: Mendel’s Contribution

Inheritance is the transmission of genetically controlled characteristics (or traits) from one generation to the next. We will now describe how Mendel studied the inheritance of characters or traits in various generations of pea plants cultivated by him. First we will discuss ‘monohybrid inheritance’ which concerns the inheritance of a single characteristic (or single trait) such as plant height. After that we will describe the dihybrid inheritance which involves the inheritance of two characteristics (or two traits) such as seed shape and seed colour.

KSEEB Class 10 SSLC Biology Chapter 4 Heredity and Evolution Monohybrid Inheritance and the Law of Segregation

• In order to trace the inheritance of a single pair of contrasting characteristics among the pea plants (like tall stem and short stem), Mendel crossed (cross-bred) the pure-bred pea plants differing in these traits and noted their occurrence in the progeny of succeeding generations.
• Mendel first crossed pure-bred tall pea plants with pure-bred dwarf pea plants and found that only tall pea plants were produced in the first generation or F₁ generation. No dwarf pea plants (or short pea plants) were obtained in the first generation of progeny. From this Mendel concluded that the first generation (or F₁ cross) showed the traits of only one of the parent plants : tallness. The trait of other parent plant, dwarfness, did not show up in the progeny of first generation.

•  Mendel then crossed the tall pea plants of the first generation (F₁ generation) and found that tall plants and dwarf plants were obtained in the second generation (or F₂ generation) in the ratio of 3 : 1. In other words in the F₂ generation, three-fourth plants were tall and one-fourth were dwarf .Mendel noted that the dwarf trait of the parent pea plant which had seemingly disappeared in the first generation progeny, reappeared in the second generation.

Mendel said that the trait of dwarfness of one of the parent pea plant had not been lost, it was merely concealed or supressed in the first generation to re- emerge in the second generation. Mendel called the repressed trait of ‘dwarfness’ as ‘recessive trait’ and the expressed trait of ‘tallness’ as the ‘dominant trait’. In this way, Mendel’s experiments with tall and dwarf pea plants showed that the traits may be dominant or recessive.

Mendel also noted that all the pea plants produced from the hybrid tall parents of F₁ generation, were either tall or dwarf. There were no plants with intermediate height (or medium height) in-between the tall and dwarf plants. In this way, Mendel’s experiment showed that the traits (like tallness and dwarfness) are inherited independently.

This is because if the traits of tallness or dwarfness had blended (or mixed up), then medium sized pea plants would have been produced. Out of a total 1064 pea plants of F₂ generation, Mendel found that there were 787 tall pea plants and 277 dwarf pea plants. The ratio of tall plants to dwarf plants comes to be 787 : 277 2.84 1, which is approximately equal to 3 : 1.

Thus, a yet another result obtained from Mendel’s monohybrid inheritance experiment is that the ratio of tall plants to dwarf plants in the F₂ generation is 3 : 1. Since tallness is a dominant trait and dwarfness is a recessive trait, so we can also say that the contrasting progeny in the F₂ generation occur in the ratio of 3 dominant to 1 recessive. The ratio 3 : 1 is known as the monohybrid ratio.

The results of monohybrid cross enabled Mendel to formulate his first law of inheritance which is called the law of segregation. According to Mendel’s first law of inheritance : The characteristics (or traits) of an organism are determined by internal ‘factors’ which occur in pairs. Only one of a pair of such factors can be present in a single gamete. We will now explain the results of monohybrid cross of tall and dwarf pea plants theoretically by using Mendel’s first law of inheritance.

Explanation of Results of Monohybrid Inheritance

•  Mendel said that each trait is determined by a pair of ‘factors´. This means that the pure-bred tall pea plant has two factors TT for the trait of tallness, and the pure-bred dwarf pea plant also has two factors tt for the trait of dwarfness.
•  The factors of inheritance of tallness TT separate into two gametes T and T, and the factors for inheritance of dwarfness tt separate into two other gametes t and t (The traits are transmitted to progeny through these gametes).
• The gametes of tall pea plant then cross with the gametes of the dwarf pea plant by the process of fertilisation to form zygotes which then produce various progeny in the F₁ generation (or first generation) which consists of all tall plants. Thus, the F₁ generation possesses one factor of inheritance from each parent plant which were carried in gametes. The parental cross is shown clearly in the following chart :

In the F₁ generation shown above, all the progeny plants have factors Tt in which T is the factor for tallness which is a dominant trait. Since all the plants in the F₁ generation have the factors Tt, so all of them are tall. The small letter t represents recessive trait of dwarfness, which does not show up in first generation in the presence of dominant trait T.

• (When two hybrid, tall pea plants (Tt) produced in the first generation (F₁) are now cross-bred with each other, then they will produce second generation (F₂) pea plants. This again happens by the separation of factors of inheritance of these tall plants into individual gametes and then crossing of the gametes during fertilisation as shown below :

We can see from the above chart that in the F₂ generation (or second generation), the pea plants produced have genotype or inheritance factors TT, Tt, Tt and tt. Now, the plants having genotype TT, Tt and Tt all contain the factor T for dominant trait ´tallness’, so all the three plants (TT, Tt and Tt) are tall. The plant having the genotype tt has both factors t for the recessive trait ‘dwarfness’, so it is a dwarf plant.

Please note that though a single copy of factor T is enough to make a plant tall but both copies of factor t (that is tt) are necessary to make a plant dwarf (or short). In the F₂ generation, we get 1 plant having genotype TT, 2 plants having genotype Tt and 1 plant having genotype tt. So, the genotypic ratio in monohydrid cross will be :

                                                                                                                  TT : Tt : tt = 1 : 2:1

Again, in the F₂ generation, we get 3 tall plants and 1 dwarf plant, so the phenotypic ratio in monohybrid cross will be : This result is the same as that obtained by Mendel through experiments.

Tall plants: Dwarf plants= 3:1

Dihybrid Inheritance and the Law of Independent Assortment

Dihybrid inheritance involves the inheritance of two pairs of contrasting characteristics (or contrasting

traits) at the same time. The two pairs of contrasting characteristics chosen by Mendel were shape and colour of seeds : round-yellow seeds, and wrinkled-green seeds .

In order to trace the inheritance of two pairs of contrasting traits, Mendel crossed pea plants having round-yellow seeds with pea plants having wrinkled-green seeds and noted their occurrence in the succeeding generations of pea plants. Mendel made the following

observations:

•  Mendel first crossed pure-bred pea plants having round-yellow seeds with pure-bred pea plants having wrinkled-green seeds and found that only round-yellow seeds were produced in the first generation. No wrinkled-green seeds were obtained in the F₁ generation. From this it was concluded that round shape and yellow colour of the seeds were dominant traits over the wrinkled shape and green colour of the seeds.
• When the F₁ generation pea plants having round-yellow seeds were cross-bred by self pollination, then four types of seeds having different combinations of shape and colour were obtained in second generation or F₂ generation. These were round-yellow, round-green, wrinkled-yellow and wrinkled-green seeds. Mendel collected a total of 556 F₂ seeds and counted them shape wise and colour wise. He got the the following result :

Round-yellow seeds           315

Round-green seeds            108

Wrinkled-yellow seeds       101

Wrinkled-green seeds        32

The phenotypic ratio of different type of seeds can be written as :

Round                Round                  Wrinkled            Wrinkled

yellow :              green :                  yellow :              green                       =           315               :      108                  :       101                 :               32

seeds                 seeds                    seeds                 seeds                       =             9                 :        3                    :        3                    :                1

Thus, the ratio of each phenotype (or appearance) of the seeds in the F2 generation is 9:3 :3 : 1. This is known as the dihybrid ratio. Mendel observed that he had started with two combinations of characteristics in seeds : round-yellow and wrinkled-green, and two new combinations of characteristics had appeared in the F₂ generation : round- green and wrinkled-yellow.

On the basis of this observation, Mendel concluded that though the two pairs of original characteristics (seed shape and colour) combine in the F₁ generation but they separate and behave independently in subsequent generations. The results of dihybrid cross enabled Mendel to formulate his second law of inheritance which is called the law of independent assortment.

According to Mendel’s second law of inheritance : In the inheritanceof more than one pair of traits in a cross simultaneously, the factors responsible for each pair of traits are distributed independently to the gametes.

Explanation of Results of Dihybrid Inheritance

In the dihybrid cross, the parent plants having the phenotype round-yellow seeds have the factors of inheritance or gene combination RRYY (in which RR are the dominant genes for round shape whereas YY are the dominant genes for yellow colour). On the other hand, the parent plants having the phenotype wrinkled-green seeds have the factors of inheritance or gene combination rryy (in which rr are the recessive genes for wrinkled shape and yy are the recessive genes for green colour). Keeping these points in mind, we can now show the dihybrid cross by drawing a chart as we did in the case of a monohybrid cross. The chart showing the dihybrid cross between pea plants having round-yellow seeds and wrinkled-green seeds is given below.

How Are Characteristics (or Traits) Transmitted to Progeny

Genes are responsible for the characteristic features (or traits) of an organism : plant or animal. The characteristics or traits of parents are transmitted to their progeny (offsprings) through genes present on their chromosomes during the process of sexual reproduction. This happens as follows. Genes work in pairs. There is a pair of genes for each characteristic of an organism (one is dominant gene and the other is recessive gene).

Each parent possesses a pair of genes for each characteristic on a pair of chromosomes. However, each parent passes only one of the two genes of the pair for each characteristic to its progeny through gametes. Thus, the male gamete and female gamete carry one gene for each characteristic from the gene pairs of parents (which are located on the pair of chromosomes).

But when a male gamete fuses with a female gamete during fertilisation, they make a new cell called zygote with a full set of genes (on a full set of chromosomes). This zygote grows and develops to form a new organism having characteristics (or traits) from both the parents which it has inherited through genes.

KSEEB Class 10 SSLC Biology Chapter 4 Heredity and Evolution

The two genes (or pair of genes) responsible for a particular characteristic are always present on the corresponding positions of the pair of chromosomes. For example, in Figure 15 the two genes for the same characteristic (length of plant stem), are present on the corresponding positions of the pair of chromosomes. One gene of the pair is for ‘tallness’ and the other is for ‘dwarfness’.

Please note that though the progeny inherits two genes (or a pair of genes) for each trait from its parents but the trait shown by the progeny depends on which inherited gene is dominant of the two. For example, if a pea plant progeny (or hybrid) inherits the gene for tallness (T) from one parent and the gene for dwarfness (t) from the other parent, then it will show the trait of ‘tallness’ and become a tall plant because the gene for tallness is dominant over the gene for dwarfness.

So, although the gene for dwarfness (t) is present in all the cells  of the hybrid plants, it does not show its effect (because it is a recessive gene).

If, however,both the parent plants pass on one copy each of the recessive gene for dwarfness (t) making the genotype (tt), then the traits of dwarfness will appear in the progeny plant. Please note that the genes for ‘tallness’ and ‘dwarfness’ are not to be considered two different genes. They are just the two forms of the same gene which controls only one characteristic feature of a plant : length of its stem. But there can be increase in length of stem making the plant tall or decrease in the length of stem, making the plant dwarf.

How do Genes Control the Characteristics (or Traits)

A gene is the section of DNA on a chromosome which codes for the formation of a protein controlling a specific characteristic (or trait) of the organism. Suppose a plant progeny has gene for the characteristic called ‘tallness’. Now, the gene for tallness will give instructions to the plant cells to make a lot of plant growth hormones.

And due to the formation of excess of plant growth hormones, the plant will grow too much and hence become tall. On the other hand, if the plant has the gene set for dwarfness, then less plant growth hormones will be produced due to which the plant will grow less, remain short and hence become a dwarf plant.

Just like plants, the characteristics (or traits) in animals (including human beings) are also transmitted from the parents through genes by the process of sexual reproduction. We will now give an example of the transmission of colour of hair from the parents (father and mother) to the child. Before we do that please keep in mind that black hair is a phenotype produced by the genotype HH or Hh. On the other hand, blonde hair (pale yellow hair) is a phenotype produced by the genotype hh. Let us give the example now.

KSEEB Class 10 SSLC Biology Chapter 4 Heredity and Evolution

A mother has black hair, the father has blonde hair (pale yellow hair), and the child has black hair . This can be explained on the basis of transmission of genes for ‘hair colour’ from the mother and father to the child as follows: Mother’s cell contain two genes HH for black hair. Both the genes HH are dominant genes, so the mother has black hair. Father’s cells contain two genes (hh) for blonde hair. The two genes hh are recessive genes, so the father has blonde hair (or pale yellow hair) .

Now, during the process of reproduction, the mother transmits one of the dominant genes H for black hair to the child and the father transmits one of his recessive genes h for blonde hair to the child. Due to this, the child has the genes Hh for her hair.

Now, the gene H for black hair is the dominant gene but the gene h for blonde hair is the recessive gene. The dominant gene H for black hair shows its effect due to which the child has black hair (see Figure 18). The recessive gene h for blonde hair cannot show its effect in the presence of dominant gene H for black hair. Please note that the genes which dominate other genes are called dominant genes, and the genes which get dominated are called recessive genes.

We will now describe the inheritance of blood groups by the children from their parents. Please note that the gene which controls the blood groups is represented by the letter I. This gene has three different forms (called alleles) which are represented as IA, IB and IO.

How Blood Groups are Inherited

A person has one of the four blood groups : A, B, AB or O. This blood group system is controlled by a gene which has three different forms denoted by the symbols Iª, I³ and Iº. The genes Iª and I³ show no dominance over each other, that is, they are codominant. However, genes IA and I³ both are dominant over the gene Iº.

In other words, the blood gene Iº is recessive in relation to genes IA and IB. Although there are three gene forms (called alleles) for blood, but any one person can have only two of them. So, the blood group of a person depends on which two forms of the genes he possesses.

• If the genotype (gene combination) is IA IA, then the blood group of the person is A. And if the genotype is IA IO even then the blood group is A (because IO is a recessive gene).
• If the genotype is IB IB, then the blood group of the person is B. And if the genotype is IB IO even then the blood group is B (because Iº is a recessive gene).
• If the genotype is IAI³, then the blood group of the person is AB.
• If the genotype is 1º10, then the blood group of the person is O.

KSEEB Class 10 SSLC Biology Chapter 4 Heredity and Evolution Sex Determination

A person can have a male sex or a female sex. The process by which the sex of a person is determined is called sex determination. Genetics is involved in the determination of the sex of a person. This can be explained as follows. The chromosomes which determine the sex of a person are called sex chromosomes. There are two types of sex chromosomes, one is called X chromosome and the other is called Y chromosome.

•  A male (man or father) has one X chromosome and one Y chromosome [see Figure 20(a)]. This means that half the male gametes or half the sperms will have X chromosomes and the other half will have Y chromosomes.

A female (woman or mother) has two X chromosomes (but no Y chromosomes). This means that all the female gametes called ova (or eggs) will have only X chromosomes.

The sex of a child depends on what happens at fertilisation :

• (a) If a sperm carrying X chromosome fertilises an ovum (or egg) which carries X chromosome, then the child born will be a girl (or female). This is because the child will have XX combination of sex chromosomes.

Please note that it is the sperm which determines the sex of the child. This is because half of the sperms have X chromosomes and the other half have Y chromosomes. Thus, there is a 50 per cent chance of a boy and a 50 per cent chance of a girl being born to the parents. This is why the human population is roughly half males and half females. From the above discussion we conclude that if the father (man or husband) contributes X sex chromosome at fertilisation through his sperm, the baby born will be a girl.

On the other hand, if the father (man or husband) contributes a Y sex chromosome at fertilisation through his sperm, then the baby born will be a boy. This means that it is the sex chromosome contributed by father (man or husband) which decides the sex of the baby which the mother (woman or wife) will give birth to. Thus, father (man or husband) is responsible for the sex of the baby (boy or girl) which is born. The belief that mother (woman or wife) is responsible for the sex of her baby is absolutely wrong.

In many ignorant Indian families, the mother (woman or wife) is held responsible for the birth of a girl child and unnecessarily harassed by her in-laws (sasural). Such people should understand that it is the husband who is responsible for the birth of a girl child (and not his wife). Moreover, a girl is no less than a boy.

In some of the animals, sex determination is also controlled by the environmental factors. For example, in some reptiles, the temperature at which the fertilised egg is incubated before hatching, plays a role in determining the sex of the offspring. It has been found that in a turtle (Chrysema picta), high incubation temperature leads to the development of female offsprings (or female progeny).

On the other hand, in the case of a lizard (Agama agama), high incubation temperature results in male offsprings (or male progeny). In some animals, such as snails, individuals can change sex, indicating that sex is not determined genetically in such animals. Before we go further and discuss acquired and inherited traits of organisms.

KSEEB Class 10 SSLC Biology Chapter 4 Heredity and Evolution Acquired and Inherited Traits

A trait (or characteristic) of an organism which is ‘not inherited’ but develops in response to the environment is called an acquired trait. For example, if a beetle does not get sufficient food for a considerable time, its weight will be reduced due to starvation. The ‘low weight’ of this beetle is an acquired trait of the beetle which has been acquired in response to the environment which contained insufficient food. Again, suppose the tail of a mouse gets cut.

The ‘cut tail’ of this mouse is also an acquired trait which has been been brought about by some agent in its environment. A man may know how to swim or roller skate or speak French or may have a scar on the face from a cut he got in an accident.

All these are acquired traits (or characteristics) which the man has picked up (or acquired) himself as he goes through life. The man is not born with these traits and he cannot pass on these traits to his children. The acquired traits of organisms cannot be passed on to their future generations. The reason for this is discussed below.

We have already studied that the traits (or characteristics) of parents are passed to their offsprings through genes in reproductive cells (or gametes) during the process of reproduction. So, for the trait of an organism to be passed on, it must have been caused by a change in the genes (or DNA) present in the reproductive cells of the organism.

In other words, only those traits can be transmitted to future generations in which changes have occurred in the genes (or DNA) present in the reproductive cells (or gametes) of parent organisms. The changes in the non-reproductive body cells of an organism cannot be inherited by its offsprings.

This will become clear from the following examples.

When the weight of a beetle is reduced too much due to starvation, then though there is a change in the normal body cells of the beetle but no change takes place in the genes (or DNA) present in its reproductive cells (or gametes). And since there is no change in the genes (or DNA) of gametes, this acquired trait (of low weight) of beetle cannot be inherited by its offsprings.

So, if some generations of beetles are low in body weight because of the availability of less food, then this is not an example of evolution because this change cannot be inherited over generations. Whenever these beetles will get sufficient food, they will become healthy again and the trait of ‘low body weight’ will disappear.

Let us discuss the other example now. If we breed some mice, all the progeny of mice will have tails, just like their parents. Now, we cut the tails of these first generation mice surgically and breed them, we will get new mice, all with full tails. It has been observed that even after cutting the tails of mice for a number of generations, a tail-less mouse is never born.

Actually, the cut tail of mice is an acquired trait which is never passed on to their progeny. This is because cutting the tails of mice does not change the genes of their reproductive cells (or gametes). And since the acquired trait of ‘cut tails’ does not bring about by a change in the genes (or DNA) of the reproductive cells. The green colour of this beetle is an inherited trait which can be passed on to the next generations.

The change from red beetle to green beetle can be considered to be an example of evolution because it helps in its survival by mixing with green bushes. Inherited traits actually mean the characteristics which we receive from our parents. This point will become more clear from the following example. Suppose a father has red curly hair, brown eyes, a snub nose and a cleft chin. Again suppose that the mother has straight black hair, blue eyes, a

long thin nose and a pointed chin . The children in the family inherit some characteristics from each of their parents. For example, two children have red hair like father but one of them has straight red hair while the other one has curly red hair. The two children have black hair like the mother. Again, two children have brown eyes like father but the other two have blue eyes like the mother. And finally, two children have snub nose and cleft chin like father whereas the other two have a long thin nose and a pointed chin.

KSEEB Class 10 SSLC Biology Chapter 4 Heredity and Evolution

There is an enormous ‘number’ and ‘types’ of living organisms (plants and animals) on this earth. In addition to this wide variety of living organisms, the remains of the dead organisms which lived in the remote past (called fossils) are also known. An important question now arises : How and from where has such a great variety of living organisms come to exist on this earth? Also, how the human beings have evolved on this earth? All these things are studied in the branch of biology called ‘evolution’.

The word ‘evolution’ has been derived from the Latin word ‘evolvere’ which means to ‘unroll’ or ‘unfold’. Evolution is a kind of gradual unfolding (or formation) of the new organisms from the pre-existing primitive organisms through slow and steady changes. We can now define evolution as follows: Evolution is the sequence of gradual changes which take place in the primitive organisms over millions of years in which new species are produced.

Since the evolution is of the living organisms, so it is also called ‘organic evolution’. It is through the constant process of evolution taking place in the organisms since the origin of life that such an enormous variety of plants and animals have come to exist on this earth at present. All the plants and animals (or organisms) which we see today around us have evolved from some or the other ancestors that lived on this earth long, long ago.

The process of evolution will become clear from the following example of ‘pterosaur’. Pterosaur is an anicient flying reptile which lived on the earth about 150 million years ago. The development of pterosaur is an example of evolution. It began life as a big lizard which could just crawl on land [see Figure 26(a)]. Over millions of years, small folds of skin developed between its feet which enabled it to glide from tree to tree . Over many, many generations, spread over millions of years, the folds of skin, and

the bones and muscles supporting them grew to form wings which could make it fly. In this way, an animal which crawled on ground evolved into a flying animal. This evolution led to the formation of a new species (of a flying reptile).

Evidences For Evolution

Various biological studies tell us that since their origin, living organisms have been undergoing changes in their organisation to evolve into new forms. A number of common features of different kinds of organisms provide evidence in favour of evolution because they can be considered to have evolved from the common ancestor. The more characteristics (or features) two species have in common, the more closely they will be related. And the more closely they are related, the more recently they will have had a common ancestor.

We will now give some of the evidences which indicate the occurrence of evolution. These evidences reinforce the view that the living organisms have evolved from common ancestors. Some of the important sources which provide evidences for evolution are:

•  Homologous organs,
•  Analogous organs, and
•  Fossils.
  We will now discuss all these evidences for evolution briefly.

 Homologous Organs Provide Evidence for Evolution
If we look at the way in which living organisms are made, we can often see quite striking similarities in btheir construction. One of these is the presence of homologous organs. Those organs which have the same basic structure (or same basic design) but different functions are called homologous organs. The homologous organs of different animals provide evidence for evolution. This will become clear from the following examples.

There are many organs in different groups of animals (or plants) which all seem to be built from the same basic design but are used for many different purposes. These are called homologous organs. For example, the forelimbs of a man, a lizard (reptile), a frog (amphibian), a bird and a bat (mammal) seem to be built from the same basic design of bones (as shown in Figure 27), but they perform different functions. The

forelimbs of a human (man) are used for grasping; the forelimbs of a lizard are used for running; the forelimbs of a frog are used to prop up the front end of its body when at rest, and also act as shock absorbers when the frog lands back on the ground after a leap; whereas the forelimbs of a bird and a bat are modified for flying. Since the forelimbs of a human, a lizard, a frog, a bird and a bat have similar structures (or design) but perform different functions, they are the homologous organs.

The presence of homologous forelimbs in humans (man), a lizard, a frog, a bird and a bat indicate that all these forelimbs have evolved from a common ancestral animal which had a ‘basic design’ limb. In other words, it tells us that a human, a lizard, a frog, a bird and a man, all have evolved from a common ancestor.

KSEEB Class 10 SSLC Biology Chapter 4 Heredity and Evolution

Thus, the presence of homologous organs in different animals provides evidence for evolution by telling us that they are derived from the same ancestor who had the ‘basic design’ of the organ on which all the homologous organs are based. Please note that the wings of a butterfly (which is an insect) and the wings of a bat cannot be considered to be homologous organs because they have different basic designs (though they are used for the same purpose of flying).

Analogous Organs Provide Evidence for Evolution

Those organs which have different basic structure (or different basic design) but have similar appearance and perform similar functions are called analogous organs. The analogous organs provide the evidence for evolution. This point will become clear from the following discussion. There are many organs in different groups of animals which seem to be built from different basic structure but appear to be similar in shape and perform similar functions.

These are called analogous organs. For example, the wings of an insect and a bird have different structures (the insects have a fold of membranes as wings which are associated with a few muscles whereas a skeleton, flesh and feathers support bird’s wings) but they perform the same function of flying . Since the wings of insects and birds have different structures (or different designs

but perform similar functions, they are analogous organs. Now, since the analogous organs have different basic design, so they do not indicate a common ancestor for the organism. The analogous organs provide evidence for the evolution in another way. The presence of analogous organs indicates that even the organisms having organs with different structures can adapt to perform similar functions for their survival under hostile environmental conditions.

Thus, the presence of analogous organs in different animals provide evidence for evolution by telling us that though they are not derived from common ancestors, they can still evolve to perform similar functions to survive, flourish and keep on evolving in the prevailing environment. The analogous organs actually provide a mechanism for evolution.

Fossils Provide Evidence for Evolution

The remains (or impressions) of dead animals or plants that lived in the remote past are known as

fossils. The fossils provide evidence for evolution. For example, a fossil bird called Archaeopteryx looks like a bird but it has many other features which are found in reptiles. This is because Archaeopteryx has feathered wings like those of birds but teeth and tail like those of reptiles. Archaeopteryx is, therefore, a connecting link between the reptiles and
birds, and hence suggests that the birds have evolved from the reptiles.

Thus, fossils provide the evidence that the present animals (and plants) have originated from the previously existing ones through the process of continuous evolution. We will now describe how fossils are formed. Usually, when organisms (plants or animals) die, their bodies will decompose by the action of micro-organisms in the presence of oxygen, moisture, etc.

Sometimes, however, the conditions in the environment are such (like absence of oxygen or moisture, etc), which do not let the body of the organism to decompose completely. It is such body (or body part) of an

organism which we get as fossil on digging the earth . In many cases the soft parts of the organisms get decomposed and what we get as a fossil is a skeleton of hard parts (like bones, etc). Even the soft parts of the plants and animals (which usually decompose quickly) are sometimes preserved as fossils in the form of their impressions inside the rocks. For example, if a dead leaf gets caught in mud, it will not decompose quickly.

The mud around the leaf will set around it as a mould, gradually harden to form a rock and retain the impression of the whole leaf. This forms a leaf fossil which can be dug out from the earth a long time later . The fossil of a dead insect caught in mud is also formed in a similar way to leaf fossil. All such preserved impressions of the body parts of the once living organisms are also called fossils.

Fossils are obtained by digging into the earth. The age of fossils can be estimated in two ways: by the relative method, and by the carbon dating method. The relative method works like this: When we dig into the earth, we find fossils at different depths. The fossils which we find in layers closer to the surface of the earth are more recent; the fossils which are found in deeper layers are older; whereas the fossils found in the deepest layers of earth are the oldest ones.

Fossils which we find today were once living objects. All the living objects contain some carbon- 14 atoms which are radioactive. When a living object dies and forms fossil, its carbon-14 radioactivity goes on decreasing gradually. In the carbon dating method, the age of fossils is found by comparing the carbon-14 radioactivity left in fossils with the carbon-14 radioactivity present in living objects today.

There are various kinds of fossils. Some of the important fossils which have been studied are those of ammonite, trilobite and dinosaur. Ammonites were the invertebrate animals (molluscs) with a flat, coiled, spiral shell which lived in the sea. The estimation of the age of ammonite fossils have told us that they are about 180 million years old. This means that ammonites lived in the sea about 180 million years ago.

Another invertebrate animal fossil which has been studied is that of trilobite Trilobites were marine arthropods which were common between 400 to 600 million years ago. Dinosaurs are extinct carnivorous or herbivorous reptiles (The word ‘dinosaur’ means ‘terrible lizard’). The estimation of the age of dinosaur fossils have told us that they first appeared on earth about 250 million years ago and became extinct about 65 million years ago. It is clear from the above discussion that we can

even study about those species which are extinct (no longer exist), by studying their fossils which are found during the digging of earth.

KSEEB Class 10 SSLC Biology Chapter 4 Heredity and Evolution Darwin’s Theory of Evolution

Charles Robert Darwin gave the theory of evolution in his famous book ‘The Origin of Species’. The theory of evolution proposed by Darwin is known as ‘The Theory of Natural Selection’. This theory is called the theory of natural selection because it suggests that the best adapted organisms are selected by nature to pass on their characteristics (or traits) to the next generation. Darwin’s theory of evolution applies to plants as well as animals.

Darwin’s theory of evolution can be described as follows:

•  Within any population, there is natural variation. Some individuals have more favourable variations than others.
•  Even though all species produce a large number of offsprings, populations remain fairly constant naturally.
•  This is due to the struggle between members of the same species and different species for food, space and mate.
•  The struggle for survival within populations eliminates the unfit individuals. The fit individuals possessing favourable variations survive and reproduce. This is called natural        selection (or survival of the fittest).
•  The individuals having favourable variations pass on these variations to their progeny from generation to generation.
•  These variations when accumulated over a long period of time, lead to the origin of a new species.

We will now understand Darwin’s theory of evolution by ‘natural selection’ by taking an example. No two animals are ever exactly alike. So some changes always appear when animals produce their progeny by sexual reproduction. For example, one of the progeny may be tall (having long legs) than the other progeny. Thus, there may be a variation of height in the progeny .

Now, the advantage of long legs to the progeny is that when no food (grass, etc.) is available on the ground, then this progeny having long legs can reach the leaves on tall trees, eat them as food and survive . On the other hand, the progeny which have short height (due to short legs) cannot reach the leaves on tall trees, they will not get any food, they will starve and hence die . Thus, nature has selected the animal with long legs to survive (because it is the fittest animal under these circumstances).

Now, since long legs help in survival, the long- legged animals will live long enough to produce their offsprings. The offspring will inherit long legs. So, all the future generations will have long-legged animals . In this way, the animals having short legs have evolved into animals having long legs due to variation. This is an example of evolution.

we can now define natural selection as follows: Natural selection is the process of evolution of a species whereby characteristics which help individual organisms to survive and reproduce are passed on to their offspring, and those characteristics which do not help are not passed on. Though Darwin’s theory was widely accepted, but it was criticised on the ground that it could not explain ‘how the variations (which lead to origin of new species) arise’. With the progress in genetics, the source of variations was explained to be the ‘genes’. Genes vary in natural population.

Genetic variation is the raw material of evolution. So, the Darwin’s theory was modified accordingly. These days, the most accepted theory of evolution is the Synthetic Theory of Evolution in which the origin of species is based on the interaction of ‘genetic variation’ and ‘natural selection’. Sometimes, a species (a type of animal or plant) may completely die out. It may become extinct. Dodo was a large flightless bird which has become extinct . Once a species is extinct, its genes are lost for ever. It cannot re-emerge at all. The small numbers of surviving tigers are a cause of worry from the

point of view of genetics because if they all die out and become extinct, their genes will be lost for ever . Our coming generations will not be able to see tigers at all. We should, therefore, make all out efforts to protect tigers (and other endangered species) to prevent them from extinction.

KSEEB Class 10 SSLC Biology Chapter 4 Heredity and Evolution Specitation

A species is a population of organisms consisting of similar individuals which can breed together and produce fertile offspring. Species can be of plants or of animals. Wheat, paddy, sunflower, lotus, mango, neem, humans, tiger, dog and cat, etc., are all examples of various types of species. The human beings who look so different from each other in terms of size, colour and looks are said to belong to the same species (Homo sapiens) because they can interbreed to produce fertile offsprings (sons and daughters).

The process by which new species develop from the existing species is known as speciation. In simple words, the formation of new species is called speciation. We will now explain how new species are formed from the existing species of various populations.

In most of the cases, new species are formed when the population of same species splits into two separate groups which then get isolated from each other geographically by the barriers such as mountain ranges, rivers or the sea. The geographical isolation of the two groups of population leads to their reproductive isolation due to which no genes are exchanged between them. However, breeding continues within the isolated populations producing more and more generations.

Over the generations, the processes of genetic drift (random change in gene frequency), and natural selection operate in different ways in the two isolated groups of population and make them more and more different from each other. After thousands of years, the individuals of these isolated groups of population become so different that they will be incapable of reproducing with each other even if they happen to meet again.

We say that two new species have been formed. From the above discussion we conclude that the important factors which could lead to the rise (or formation) of a new species are the following :

•  Geographical isolation of a population caused by various types of barriers (such as mountain ranges, rivers and sea). The geographical isolation leads to reproductive isolation due to which there is no flow of genes between separated groups of population.
• Genetic drift caused by drastic changes in the frequencies of particular genes by chance alone.
•  Variations caused in individuals due to natural selection.

It should be noted that geographical isolation is the major factor in the speciation of sexually reproducing animals because it interrupts the flow of genes between their isolated populations through the gametes.

The geographical isolation, however, cannot be a major factor in the speciation of a self- pollinating plant species because it does not have to look to other plants for its process of reproduction to be carried out. Geographical isolation also cannot be a major factor in the speciation of an asexually reproducing organism because it does not require any other organism to carry out reproduction.

KSEEB Class 10 SSLC Biology Chapter 4 Heredity and Evolution of Eyes

The eye is a very important organ for animals. The eye is a complicated organ which cannot be generated

by a single DNA change. The complex body organs of animals such as eyes have been created in ‘stages’ over many generations. First of all the rudimentary eye (basic eye) like that of a flatworm (Planaria) was formed . The eyes of flatworm are very simple that are actually just ‘eye-spots’ which can detect light. Even these rudimentary eyes provide a survival advantage to flatworm.

Starting from this basic design, more and more complex eyes were then evolved in various organisms. Most of the animals have eyes. For example, the insects, octopus and invertebrates, all have eyes. The structure of eyes in each of these organisms is, however, different which suggests their separate evolutionary origins. The evolution of eye is an example of evolution by stages.

KSEEB Class 10 SSLC Biology Chapter 4 Heredity and Evolution of Feathers

Sometimes an evolutionary change produced in an organism for one purpose later on becomes more useful for an entirely different function. For example, birds evolved feathers as a means of providing insulation to their bodies in cold weather but later on these feathers became more useful for the purpose of flying.

Even some dinosaurs had feathers though they could not fly by using these feathers. Birds, however, adapted feathers for flying. The presence of feathers on birds tells us that the birds are very closely related to reptiles because dinosaurs (which had feathers) were reptiles.

KSEEB Class 10 SSLC Biology Chapter 4 Heredity and Evolution By Artificial Selection

In the evidence for evolution we have studied that very dissimilar looking structures can evolve from a common ancestral body design. But that was all guesswork about what happened in history long time ago. We will now give an example from the present time which will show that different looking organisms can in fact be created from the same basic design of the ancestor. The wild cabbage plant is a good example to prove that entirely different looking organisms can evolve from the same organism by the process of evolution.

The only difference is that here we are using artificial selection for evolution in place of natural selection. This will become clear from the following discussion. The farmers have been cultivating wild cabbage as a food plant for over two thousand years and have produced (or evolved) entirely different looking vegetables like cabbage, broccoli, cauliflower, kohlrabi and kale from it by artificial selection .

•  Some farmers wanted to have very short distances between the leaves of wild cabbage and produced the common variety of ‘cabbage’.
• When farmers opted for the arrested flower development of wild cabbage plant, it led to the production of another variety of cabbage called ‘broccoli’.
• Some farmers went in for sterile flowers of wild cabbage and developed another variety of cabbage called ‘cauliflower’.

•  When farmers opted for the swollen parts of wild cabbage, it led to the evolution of a yet another variety of cabbage called ‘kohlrabi’.
• And finally, the farmers wanted to grow large leaves of wild cabbage and ended up producing a leafy vegetable called ‘kale’ which is also a variety of wild cabbage.

Evolution Should Not be Equated With Progress

There is no real progress in the concept of evolution. Evolution is just the production of diversity of life forms and shaping of this diversity by the environmental selection. The only progress in evolution appears to be that more and more complex body designs of organisms have emerged over the ages.

This will become clear from the following examples. When a new species is formed, it is not necessary that the old species will disappear (or get eliminated) from earth. It will all depend on the environment. Also it is not as if the newly formed species are in any

way better than the older ones. It is simply that genetic drift and natural selection processes have combined to form a population having different body design which cannot interbreed
with the older population.

It is a common belief that chimpanzees are the ancestors of human beings. It is, however, not true that human beings have evolved from chimpanzees. Actually, both chimpanzees and human beings had a common ancestor long time ago. The two offsprings of that ancestor evolved in their own separate ways to form the modern day chimpanzees and human beings.

Again, it is not as if the body designs of older organisms were inefficient. This is because many of the older and simpler forms of organisms still survive on earth. For example, one of the simplest and primitive life forms called ‘bacteria’ still inhabit some of the most inhospitable (or unfavourable) habitats such as hot springs, deep-sea thermal vents and the ice in Antarctica. Most other organisms cannot survive in such harsh environments.

KSEEB Class 10 SSLC Biology Chapter 4 Heredity and Evolution Human Evolution

Human evolution has been studied by using the various tools of tracing evolutionary relationships like excavating (digging earth), carbon-dating, studying fossils and determining DNA sequences. There is so much diversity of human body and features on the earth that for a long time people used to talk about different ‘races’ of human beings. The human races were even identified on the basis of their skin colour and named as white, black, yellow or brown.

It is now known that the so called human races have not evolved differently. In fact, there is no biological basis for dividing human beings into different ‘races’. All human beings (whether, white, black, yellow or brown) are a single species (called Homo sapiens). It has now been established by research that the earliest members of the human species (Homo sapiens) came from Africa.

So, irrespective of where we have lived for the past few thousand years, we all come from Africa. In other words, our genetic footprints tell us that we have African roots. About hundred thousand years ago, some of our ancestors left Africa while others stayed back. Those who left Africa slowly spread across the whole earth.

Mendel’s experiments tell us the mode of inheritance of traits from one generation to the next and Darwin’s theory of evolution tells us how organisms develop from simple to more complex forms. But neither tells us anything about how life originated on earth (or began on earth). We will now discuss the origin of life on earth briefly.

KSEEB Class 10 SSLC Biology Chapter 4 Heredity and Evolution Origin of Life on Earth

A British scientist J.B.S. Haldane suggested in 1929 that life must have developed from the simple inorganic molecules (such as methane, ammonia, hydrogen sulphide, etc.) which were present on the earth

soon after it was formed. He said that the conditions on earth at that time (including frequent lightning) could have converted simple inorganic molecules into complex organic molecules which were necessary for life. These complex organic molecules must have joined together to form first primitive living organisms. Haldane also suggested from theoretical considerations that life (or living organisms) originated in the sea water.

The theory of origin of life on earth proposed by Haldane was confirmed by experiments conducted by Stanley L. Miller and Harold C. Urey in 1953. They assembled an apparatus to create an early earth atmosphere which was supposed to consist of gases like methane, ammonia and hydrogen sulphide, etc., (but no oxygen), over water. This was maintained at a temperature just below 100°C and electric sparks were then passed through the mixture of gases (to simulate lightning) for about one week.

At the end of one week, it was found that about 15 per cent of carbon (from methane) had been converted into simple compounds of carbon including ‘amino acids’ which make up protein molecules found in living organisms. This experiment provides the evidence that the life originated from inanimate matter (or lifeless matter) like inorganic molecules.

KSEEB SSLC Class 10 Social Science Notes History

• Chapter 1 Advent of Europeans to India Notes
• Chapter 2 The Extension of the British Rule Notes
• Chapter 3 The Impact of British Rule in India Notes
• Chapter 4 Opposition to British Rule in Karnataka Notes
• Chapter 5 Social and Religious Reformation Movements Notes
• Chapter 6 The First War of Indian Independence (1857) Notes
• Chapter 7 Freedom Movement Notes
• Chapter 8 Era of Gandhi and National Movement Notes
• Chapter 9 Post Independent India Notes
• Chapter 10 The Political Developments of 20th Century Notes

KSEEB SSLC Class 10 Social Science Notes Political Science

• Chapter 1 The Problems of India and their Notes
• Chapter 2 Indian Foreign Policy Notes
• Chapter 3 India’s Relationship with Other Countries Notes
• Chapter 4 Global Problems and India’s Role Notes
• Chapter 5 International Institutions Notes

KSEEB SSLC Class 10 Social Science Notes Sociology

• Chapter 1 Social Stratification Notes
• Chapter 2 Labour Notes
• Chapter 3 Social Movements Notes
• Chapter 4 Social Problems Notes

KSEEB SSLC Class 10 Social Science Notes Geography

• Chapter 1 Indian Position and Extension Notes
• Chapter 2 Indian Physiography Notes
• Chapter 3 Indian Climate Notes
• Chapter 4 Indian Soils Notes
• Chapter 5 Indian Forest Resources Notes
• Chapter 6 Indian Water Resources Notes
• Chapter 7 Indian Land Resources Notes
• Chapter 8 Indian Mineral & Power Resources Notes
• Chapter 9 Indian Transport and Communication Notes
• Chapter 10 Indian Industries Notes
• Chapter 11 Indian Natural Disasters Notes
• Chapter 12 Indian Population Notes

KSEEB SSLC Class 10 Social Science Notes Economics

• Chapter 1 Development Notes
• Chapter 2 Rural Development Notes
• Chapter 3 Money and Credit Notes
• Chapter 4 Public Finance and Budget Notes

KSEEB SSLC Class 10 Social Science Notes Business Studies

• Chapter 1 Bank Transactions Notes
• Chapter 2 Entrepreneurship Notes
• Chapter 3 Globalization of Business Notes
• Chapter 4 Consumer Education and Protection Notes

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination Notes

All the living organisms (plants and animals) respond and react to changes in the environment around them. The changes in the environment to which the organisms respond and react are called stimuli (singular of stimuli is stimulus). The living organisms show response to stimuli such as light, heat, cold, sound, smell, taste, touch, pressure, pain, water, and force of gravity, etc.

The response of organisms to a stimulus is usually in the form of some movement of their body part. For example, if a man touches a very hot utensil accidently, he quickly pulls his hand away from the hot utensil. Here, heat is the stimulus and the man reacts by moving his hand away from the hot utensil. Similarly, when the sun is bright, we close our eyes. In this case, light is the stimulus and we react by closing the eyes.

We know that a sunflower always faces the sun. Here, sunlight is the stimulus and sunflower reacts by bending (or moving) towards the sun. We eat food when we are hungry (and need energy). In this case, hunger is the stimulus and we react by eating food. From the above discussion we conclude that the reaction to stimuli is a characteristic property of the living organisms. Another word which is also used in place of ‘reaction’ is ‘response’. So, we can also say that the response to stimuli is a characteristic property of the living organisms.

Both, plants and animals react (or respond) to various stimuli around them. But the method of reacting to stimuli is not similar in plants and animals. They react to stimuli in different ways. For example, plants bend towards light but animals do not bend towards light. The animal Amoeba reacts to the presence of food by moving towards the food particle. Similarly, Amoebae tend to aggregate (collect together) in moderately warm water which is their reaction to the stimulus called heat. Amoeba and other protozoa react to the mechanical obstacles by avoiding them.

We find that the Amoeba (which is an animal) can react to different stimuli in different ways. The animals can react to stimuli in many different ways because they have a nervous system and an endocrine system involving hormones. The plants, however, react to stimuli in a very limited way. This is because the plants do not have a nervous system like the animals have. The plants use only the hormones for producing reaction to external stimuli.

From all the above examples we conclude that when a stimulus acts on our body, then we react (or respond) in a manner which is in the best interest of our body. The reaction (or response) which we give to the stimulus involves many organs of our body. It is, therefore, necessary that all the concerned organs should work with one another in a systematic manner so as to produce the required reaction. In other words, the various organs should co-operate with one another to provide proper reaction to the stimulus.

The working together of the various organs of an organism in a systematic manner so as to produce a proper response to the stimulus, is called coordination. We will now discuss the control and coordination in plants, animals and human beings, one by one. Let us start with control and coordination in plants.

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination In Plants

The plants do not have a nervous system and sense organs like eyes, ears, or nose, etc., like the animals, but they can still sense things. The plants can sense the presence of stimuli like light, gravity, chemica water, and uch, etc., and respond to them. The plants can sense things like light, gravity, chemicals, water, and touch, etc., by the action of hormones in them. The stimuli like light, gravity, chemicals, water, and touch, etc., are called environmental changes.

So, we can also say that the plants coordinate their behaviour against environmental changes by using hormones. The hormones in plants do not act the same way as in animals. The hormones in plants coordinate their behaviour by affecting the growth of a plant. And the effect on growth of the plant can result in the movement of a part of the plant like shoot (stem) or root, etc. Animals use both nervous system and hormones for coordination of their activities.

Plants have no nervous system, so plants use only hormones for coordination. Thus, the reaction (or response) of plants to different stimuli like light, gravity, chemical substances, water, and touch etc., is due to the effect of hormones. Please note that animals can respond quickly because they have a nervous system. Plants cannot respond quickly because they have no nervous system. The plants respond to various stimuli very slowly by growing. So, in most of the cases, the response of a plant to a stimulus cannot be observed immediately. It usually takes a considerable time to observe the effect of a stimulus on a plant

From the above discussion we conclude that the function of control and coordination in plants is performed by the chemical substances called plant hormones. Please note that the plant hormones are also called phytohormones (‘phyto’ means ‘plant’). Before we discuss the various types of plant hormones, we should know the meanings of ‘dormancy’ and ‘breaking of dormancy’. A resting, inactive condition in which metabolism almost stops is called dormancy.

The seed of a plant is inactive or dormant. It has dormancy. A seed must have certain conditions like water, warmth, air and hormones to break dormancy and germinate to form a seedling (which then grows into a plant). Another part of a plant having dormancy is the bud. The bud is a young, undeveloped shoot of a plant which on breaking dormancy can form a branch, a leaf or a flower depending on its position in the plant. The breaking of dormancy of a bud also requires certain plant hormones. Keeping these points in mind, we will now discuss the various types of plant hormones.

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination Plant Hormones

The control and coordination in plants is done by plant hormones (or phytohormones). The plant hormones coordinate the activities of the plant by controlling one or the other aspect of the growth of the plant. So, the plant hormones are also known as plant growth substances. The growth of a plant can be divided into three stages : cell division, cell enlargement and cell differentiation (or cell specialisation), and these stages have particular locations in a plant. These three stages of plant growth as well as promotion of dormancy, breaking of dormancy, stomata control, falling of leaves, fruit growth, ripening of fruits and ageing in plants are controlled by the various plant hormones.

There are four major types of plant hormones (or phytohormones) which are involved in the control and coordination in plants. These are :

• Auxins,
• . Gibberellins,
•  Cytokinins, and
•  Abscisic acid (ABA).

Auxins, gibberellins and cytokinins are the plant hormones which promote growth of plants. On the other hand, abscisic acid is a plant hormone which inhibits (or prevents) the growth. The detailed functions of the various plant hormones are given below.

•  Auxins are the plant hormones which promote cell enlargement and cell differentiation in plants. Auxins also promote fruit growth. Auxin hormone controls a plant’s response to light and gravity. In other words, auxin hormone is responsible for the phototropic and geotropic responses of plants. Auxin is made by cells at the tip of stems and roots. Auxin moves away from light, and towards gravity. Auxin has opposite effect on the growth of stem and roots. Auxin speeds up growth in stem but it slows down growth in roots. Synthetic auxins are applied in agriculture and horticulture.
•  Gibberellins are plant hormones which promote cell enlargement and cell differentiation in the presence of auxins. Gibberellins help in breaking the dormancy in seeds and buds. They also promote growth in fruits. Gibberellin hormone is involved mainly in shoot extensions. Gibberellin stimulates elongation of shoots of various plants.
• Cytokinins are the plant hormones which promote cell division in plants. Cytokinins also help in breaking the dormancy of seeds and buds. They delay the ageing in leaves. Cytokinins promote the opening of stomata. They also promote fruit growth.
• Abscisic acid is a plant hormone which functions mainly as a growth inhibitor. Abscisic acid promotes the dormancy in seeds and buds (this is the opposite of breaking of dormancy). It also promotes the closing of stomata. Abscisic acid promotes the wilting and falling of leaves (which is called abscission). It also causes the detachment of flowers and fruits from the plants.

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination Plant Movements

The plants are fixed at a place with their roots in the ground, so they cannot move from one place to another. That is, plants do not show locomotion (movement of the entire body). However, movements of the individual parts or organs of a plant (like shoot, root, leaves, etc.) are possible when they are subjected to some external stimuli like light, force of gravity, chemical substances, water, and touch, etc.

These movements of the plant part are usually caused by an unequal growth in its two regions by the action of plant hormones, under the influence of the stimulus.

For example, the auxin hormone is made and secreted by the meristematic tissue at the tip of stem (or tip of shoot). The auxin hormone speeds up the growth in stems. So, if one side of a stem has more auxin than the other side, then the side of stem having more auxin hormone will grow faster than the other side (having less auxin hormone). This will cause the stem to bend. And when the stem bends to one side, we say that the stem is showing movement.

This movement (or bending) of the stem has been caused by its growth. So, we can say that the bending of a stem (or shoot) (when exposed to light from one side) is a growth movement. In fact, the movement in any part of a plant is usually a growth movement. Please

note that when a plant part shows movement, it remains attached to the main body of the plant. It does not get detached from it. We will now discuss tropism in which the part of a plant shows movement in response to various stimuli. The plant movements made in response to external stimuli fall into two main categories : tropisms and nasties.

Though all the tropisms are growth movements but nasties may be growth movements or growth- independent movements. In tropisms, the direction of stimulus determines the direction of movement of the plant part but in nasties the direction of movement is not determined by the direction of stimulus.

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination Tropisms

A growth movement of a plant part in response to an external stimulus in which the direction of stimulus determines the direction of response is called tropism. Thus, tropism is a directional movement of the part of a plant caused by its growth. The growth of a plant part in response to a stimulus can be towards the stimulus (in the direction of stimulus) or away from the stimulus (against the direction of stimulus) due to which we can have a positive tropism or negative tropism, respectively. So :

• . If the growth (or movement) of a plant part is towards the stimulus, it is called positive tropism, and
• If the growth (or movement) of a plant part is away from the stimulus, then it is called negative tropism.

We will now give an example of tropism. When a growing plant is exposed to light from only one side, then it responds by bending its stem (or shoot) towards the light. This is an example of phototropism (which is caused by the ‘light’ acting as ‘stimulus’. ‘Photo’ stands for ‘light’). The bending of the plant stem (or shoot) towards light is actually positive phototropism.

Types of Tropisms

There are five common stimuli in the environment : light, gravity, chemicals, water and touch (or contact). These five stimuli give us five types of tropisms : phototropism, geotropism, chemotropism, hydrotropism and thigmotropism. In phototropism, the stimulus is light; in geotropism the stimulus is gravity, in chemotropism the stimulus is a chemical, in hydrotropism the stimulus is water, and in thigmotropism the stimulus is touch (of a solid surface). It is obvious that the tropisms are named according to the stimulus.
This will become clear from the following table.

We will now give the definitions of all the five types of tropisms.

• The movement of a plant part in response to light is called phototropism. In other words, the response of a plant to light is called phototropism. If the plant part moves towards light, it is called positivephototropism. On the other hand, if the plant part moves away from light, then it is called negativephototropism. The stem (or shoot) of a growing plant bends towards light, so the stem (or shoot) of a plant shows positive phototropism. On the other hand, the roots of a plant move away from light, so the roots of a plant show negative phototropism.

• The movement of a plant part in response to gravity is called geotropism. In other words, the response of a plant to gravity is called geotropism. If the plant part moves in the direction of gravity, it is called positive geotropism. On the other hand, if the plant part moves against the direction of gravity, it is negative geotropism (Please note that the force of gravity acts in the downward direction). Now, the roots of a plant move downwards in the direction of gravity, so the roots of a plant show positive geotropism. On the other hand, the stem (or shoot) of a plant moves upwards against the direction of gravity, so the stem (or shoot) of a plant shows negative geotropism

• The movement of a plant part in response to a chemical stimulus is called chemotropism. In other words, the response of a plant to chemical stimulus is called chemotropism. If the plant part shows movement (or growth) towards the chemical, it is called positive chemotropism. On the other hand, if the plant part shows movement (or growth) away from the chemical, then it is called negative chemotropism. The growth of pollen tube towards the ovule during the process of fertilisation in a flower is an example of chemotropism (It is actually positive chemotropism). In this case the pollen tube grows towards the sugary substance (chemical) secreted by the ripe stigma of carpel in the flower.
• The movement of a plant part in response to water is called hydrotropism. In other words, the response of a plant part to water is called hydrotropism. If the plant part moves towards water, it is called positive hydrotropism. On the other hand, if the plant part moves away from water, then it is called negative hydrotropism. The roots of a plant always go towards water, so roots are positively hydrotropic

The directional growth movement of a plant part in response to the touch of an object is called thigmotropism. The climbing parts of the plants such as tendrils grow towards any support which they happen to touch and wind around that support. So, tendrils of plants are positively thigmotropic. We will now describe a plant’s response to light, gravity, chemicals, water and touch with the help of diagrams.

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination Response of Plants To Light: Phototropism

Plants need sunlight, so the stems (or shoots) respond to sunlight by growing towards it. The plants also turn their leaves to face the sun. This makes sure that the leaves get as much sunlight as possible. When a plant is grown in the open ground with the sunlight coming from above, then the stem of plant grows straight up.

If, however, the plant is grown with sunlight coming from one side, then the stem of plant bends towards the direction from which the sunlight comes. The root of plant, however, bends away from the direction from which the sunlight comes. We will now describe an experiment to show the response of plant parts to light.

We take a potted plant growing in a transparent glass jar. When this potted plant is kept in the open space, the sunlight falls from above due to which the stem of plant grows straight up towards the source of light ´sun’. The root of plant also grows straight but in the downward direction.

Let us now keep the potted plant having straight stem and straight root near the window in a dark room so that sunlight falls on it from the right side (through the window) only. After some days we will see that the stem of the plant bends towards the right side from where the light is coming. This observation shows that the stem of plant responds to light and bends towards it. Even the leaves of the plant turn towards the sun so as to obtain the maximum sunlight. Thus, the stem (and leaves) of a plant are positively phototropic.

Now, if we look at the root of the plant in Figure 10(b), we find that the root bends to the left side away from the light. This observation shows that the root of plant responds to light by growing away from it. Thus, the root of plant is negatively phototropic. We will now explain the bending of a plant stem towards sunlight. The plant stem responds to light and bends towards it due to the action of ‘auxin hormone’. This happens as follows:

•  When sunlight comes from above, then the auxin hormone present in the tip of the stem spreads uniformly down the stem. Due to the equal presence of auxin, both the sides of the stem (A and B) grow equally rapidly. And the stem grows straight up.

• When the light falls only on the right side of the stem [side B in Figure 11(b)], then the auxin hormone collects in the left side (shady side A) of the stem, away from light. This is because auxin hormone prefers to stay in shade.
• Now, more auxin hormone is present in the left side of stem but not on its right side. Due to more auxin hormone, the left side (A) of stem grows faster than its right side (B) where there is no auxin. Since the left side of stem grows faster and becomes longer than its right side, therefore, the stem bends towards the right side (in the direction of light). We can also explain the bending of a plant root away from light by the action of auxin hormone
• . For this we have to remember that the effect of auxin on the growth of a root is exactly opposite to that on a stem. Thus, though auxin hormone increases the rate of growth in a stem but it decreases the rate of growth in a root. Now, the side of a  root away from light will have all the auxin concentrated in it. Due to this, the side of root which is away from light will grow slower than the other side and make the root bend away from light. Please draw the diagram to show the bending of plant root away from light yourself.

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination The Response of Plants to Gravity : Geotropism

The force with which the earth pulls all the things towards it, is called gravity. The force of gravity always acts in the downward direction. The response of plants to gravity is called geotropism. Geotropism is also known as gravitropism.

• The roots of plants always grow downward in response to gravity. This makes sure that they will find soil and water.
• The stems (or shoots) of plants always grow up, away from the pull of gravity. This makes sure that they will get light.
  The movement of plant roots towards the earth and that of stem away from earth, both are cases of geotropism. Since the roots grow down towards the pull of gravity, so the downward growth (or downward movement) of roots is called positive geotropism. The stem (or shoot) grows upwards, away from the pull of gravity, so the upward growth (or upward movement) of stem or shoot is called negative geotropism. The response of plants to gravity (or geotropism) will become more clear from the following experiment.
•  We take a potted plant growing in a transparent glass jar. When this potted plant is kept in the normal position, we can see that its roots are growing downwards and its stem is growing upwards
• Let us now tilt the potted plant and keep the pot horizontally on its side as shown.  In this position, the roots and stem both are parallel to the ground (or earth). Allow the plant to remain in this position for a few days.
•  After a few days we will find that the roots of the potted plant bend downwards towards the earth and the stem of plant bends upwards, away from the earth. The roots of plant grow downwards in response to the pull of gravity. The stem of plant responds to gravity in the opposite way, by growing upwards (away from the pull of gravity). Response of Plants to Chemicals : Chemotropism The growth (or movement) of a plant part due to chemical stimulus is known as chemotropism.

The growth (or movement) of a pollen tube towards the ovule induced by a sugary substance as stimulus, is an example of chemotropism. This can be explained as follows: The ripe stigma in the carpel of a flower secretes a chemical substance (which is a sugary substance) into the style towards the ovary.

This sugary substance acts as a stimulus for the pollen grains which fall on the stigma of the carpel. The pollen grain responds to this stimulus by growing a pollen tube in the downward direction into the style of the carpel and reaches the ovule in the ovary of the flower for carrying out fertilisation. This growth of the pollen tube in response to a chemical substance secreted by the stigma of a flower is an example of chemotropism.

Response of Plants to Water : Hydrotropism

The roots of plants always go towards water, even if it means going against the pull of gravity. Though roots normally grow downwards but in order to reach water, they can grow sideways or even upwards! The roots grow in the direction of source of water so as to obtain water for the developing plant.
Since roots always grow (or move) towards water, therefore, roots are positively hydrotropic. When the roots bend by growing towards water, it appears that they move towards water. We will now describe an experiment to demonstrate hydrotropism. This will show us the response of roots to water. We take two glass troughs A and B and fill each one of them two-thirds with soil (see Figure 14). In trough A we plant a tiny seedling.

In trough B we plant a similar seedling and also place a small ‘clay pot’ inside the soil . Water the soil in trough A daily and uniformly. Do not water the soil in trough B but put some water in the clay pot buried in the soil. Leave both the troughs for a few days.

Now, dig up the seedlings carefully from both the troughs without damaging their roots. We will find that the root of seedling in trough A is straight. On the other hand, the root of seedling in trough B is found to be bent to the right side (towards the clay pot containing water). This can be explained as follows. In trough A, the root of seedling gets water from both sides (because the soil is watered uniformly).

But in trough B, the root gets water oozing out from the clay pot which is kept on the right side. So, the root of seedling in trough B grows and bends towards the source of water to the right side. This experiment shows that the root of a plant grows towards water. In other words, the root of a plant is positively hydrotropic.

Directional Response of Plants to the Touch of an Object: Thigmotropism

There are some plants called ‘climbing plants’ which have weak stems and hence cannot stand upright (or erect) on their own. The climbing plants have climbing organs called tendrils. Tendrils are the thin, thread-like growths on the stems or leaves of climbing plants. Thus, there are two types of tendrils : stem tendrils and leaf tendrils. Tendrils are sensitive to the touch (or contact) of other objects.

That is, tendrils have cells which can sense their contact with a nearby solid object like a bamboo stick, or the stem of another plant. So, when a tendril touches an object, then the side of tendril in contact with the object grows slowly than its other side. This causes the tendril to bend towards the object by growing towards it, wind around the object and cling to it. The winding movement of the tendril of a climbing plant is an example of thigmotropism. The stimulus in thigmotropism is the touch (or contact) of an object. The winding movement of the tendril of a plant around a nearby object gives support to the plant having a weak stem.

Thigmotropism is often seen in plants having tendrils. Tendrils are positively thigmotropic which means that they grow towards things they happen to touch. The plants having stem tendrils or leaf tendrils which are positively thigmotropic climb up artificial supports, other plants or fences very easily. The plants such as bitter gourd (karela), bottle gourd (lauki), grape vine and passion flower have stem tendrils which are positively thigmotropic and make these plants to climb up by winding around various types of supports. The plants such as peas and glory lily have leaf tendrils which are positively thigmotropic.

These leaf tendrils also make their plants to climb up by winding around various types of nearby supports. From the above discussion we conclude that tendrils are the climbing organs of the plants which are positively thigmotropic.

The Usefulness of Tropic Movements 

The various types of tropic movements help the plants to survive. For example, even if a seed is planted upside down, its root will still grow downwards into earth because it is positively geotropic (see Figure 16). The root will also grow towards water because it is positively hydrotropic. Similarly, the shoot of such a seed will grow upwards because it is negatively geotropic and towards light because it is positively phototropic. These tropic movements help the plants to obtain water and nutrients from soil and light from the sun, which are necessary for their growth and survival.

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination Nasties

We have just studied that in tropism, a plant part either moves towards the stimulus or away from the stimulus. However, in some plants, the movement of the plant part is neither towards the stimulus nor away from the stimulus. That is, the movement of plant part in some plants is not in a particular direction with respect to stimulus. The movement of a plant part in response to an external stimulus in which the direction of response is not determined by the direction of stimulus is called nastic movement. Nastic movements of plants are also called nasties. The nastic movements of plants are induced by stimuli such as heat, light, touch (or contact), etc.

The main difference between tropic and nastic movements is that tropic movement is a directional movement of a plant part but nastic movement is not a directional movement of the plant part with respect to the stimulus. The direction of nastic movement is not determined by the direction from which the stimulus is applied. In nastic movement, from whichever direction the stimulus is applied, it affects all the parts of the organ of a plant equally and they always move in the same direction. Nastic movements are mostly exhibited by the flat organs of the plants like ‘leaves’ and ‘petals of flowers’. Some of the examples of the nastic movements of plants (or nasties) are given below :

•  The folding up of the leaves of a sensitive plant (Mimosa pudica) on touching is an example of nastic movement. Here the stimulus is touch.
•  The opening up of the petals of dandelion flowers in morning in bright light and closing in the evening when the light fades is an example of nastic movement. In this case the stimulus is light.
•  The closing of the petals of moonflower in the morning in bright light and opening at dark when the light fades is also an example of nastic movement. In this case also the stimulus is light. Please note that though all tropisms are growth movements but all nasties (or nastic movements) are not growth movements. Nastic movements may or may not be growth movements.
• For example, the folding up of the leaves of a sensitive plant on touching is not a growth movement but the opening and closing of petals of flowers by the action of sunlight is a growth movement. We have just said that most of the movements of the plant parts are caused by their growth. Now, since the growth of a plant part is usually a slow process, therefore, most of the movements of plant parts are very slow. There are, however, some exceptions.
• We will now describe the movement of a plant part (leaves) which is unusually fast and takes place almost immediately. It is the folding up of the leaves of a sensitive plant when touched with a finger (or any other object). This is discussed below under the topic on thigmonasty.

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination Thigmonasty

The non-directional movement of a plant part in response to the touch of an object is called thigmonasty. In other words, thigmonasty is the nastic movement of a plant part in response to touch. Thus, the stimulus in thigmonasty is the ‘touch’. An example of the nastic movement in plants caused by touch (or thigmonasty) is provided by the sensitive plant (Mimosa pudica) which is also known as touch- me-not plant. It is called chhui-mui in Hindi.

If we touch the leaves (or rather leaflets) of the sensitive plant with our fingers, then its leaves fold up and droop almost immediately. The folding up of the leaves of sensitive plant on touching, is an example of nastic movements in plants (in which the stimulus is the ‘touch’ of our fingers

In this case, the ‘touch’ of our fingers is the stimulus and the leaves respond by ‘folding up’. Please note that the folding of leaves of a sensitive plant is not a case of tropism (like thigmotropism) because in this case the direction of movement of leaves does not depend on the direction of stimulus (touch). We will now describe how the leaves of a sensitive plant fold up when touched.

The sensitive plant has pad-like swellings called ‘pulvini’ at the base of each leaf. (The singular of pulvini is pulvinus). The pulvini contain a lot of water in their cells. Due to the internal ‘water pressure’ in them (called turgor), all the pulvini are very firm and hold the leaves above them upright

The pulvini have also large intercellular spaces (empty spaces) between their cells. The folding up of the leaves of a sensitive plant on touching is due to the sudden loss of water from pad-like swellings called ‘pulvini’ present at the base of all leaves of the sensitive plant which make the pulvini lose their firmness causing the leaves to droop and fall.

This happens as follows. When the leaves of sensitive plant (having pulvini at their base) are touched with a finger, then an electrical impulse is generated which travels through ordinary cells (because there are no nerve cells insensitive plant or other plants).

This electrical impulse acts on a plant hormone. The plant hormone makes the water migrate from the cells of one half of a pulvinus to the intercellular spaces in the other half of pulvinus. This loss of water from half of pulvinus causes the pulvinus to lose its firmness making the leaf to fold [see Figure 18(b)]. Similarly, all the pulvini lose firmness and become limp due to which all the leaves above them collapse and fold up. At a gap of 15 to 30 minutes after the leaves have folded, water usually diffuses back into same cells of pulvinus from which it left, and the leaf returns to its original position

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination Photonasty

The non-directional movement of a plant part (usually petals of flowers) in response to light is called photonasty. In other words, photonasty is the nastic movement of a plant part (like petals of flowers) in response to light. Thus, the stimulus in photonasty is light.

A dandelion flower opens up in the morning in bright light but closes in the evening when the light fades and it gets dark. The opening and closing of petals of dandelion flowers in response to the intensity of light is an example of nastic movement in which the stimulus is light. In other words, it is an example of photonasty. The moonflower behaves exactly opposite to that of dandelion flowers in respect of response to light.

The petals of moonflower close during the day when there is bright light but open up at night when it is dark and there is no light (see Figure 20). This is also an example of photonasty. Please note that the opening and closing of flowers in response to light (or photonasty) are growth movements. Petals open when their inner surfaces grow more than their outer surfaces. On the other hand, petals close when their outer surfaces grow more than their inner surfaces.

Before we end this discussion, we would like to give the functions of plant hormones. Functions of Plant Hormones (or Phytohormones) The plant hormones (or phytohormones) regulate many functions in plants. The various functions in plants which are regulated by the plant hormones (or phytohormones) are :

• Germination of seeds (or Breaking the dormancy of seeds),
•  Growth of root, stem and leaves,
• Movement of stomata (or stomatal movement) in leaves,
•  Flowering of plants,
•  Ripening of fruits, and
•  Phototropism, geotropism, chemotropism, hydrotropism, thigmotropism and nastic movements.

The multicellular animals (except sponges) have specialised cells called nerve cells (or neurons) to respond to stimuli and coordinate their activities. A system made up of nerve cells is called nervous system. The coordination in simple multicellular animals takes place through nervous system only. For example, Hydra is a simple multicellular animal. The nervous system of Hydra consists of a network of nerve cells joined to one another and spread throughout its body (see Figure 21).

The control and coordination in higher animals called vertebrates (including human beings) takes place through nervous system as well as hormonal system called endocrine system. Before we describe the control and coordination in humans, it will be good to know something about sense organs, receptors and effectors. These are described below. There are five sense organs in our body: eyes, ears, nose, tongue and skin . We receive a variety of information from the environment around us through the sense organs.

The sense organs contain receptors. A receptor is a cell (or a group of cells) in a sense organ which is sensitive to a particular type of stimulus (or a particular type of change in the environment) such as light, sound, smell, taste, heat, pressure, etc. The different sense organs contain receptors for detecting different stimuli. The eyes have light receptors (which can detect light),

ears have sound receptors (which can detect sound), nose has smell receptors (which can detect smell), tongue has taste receptors (which can detect taste) whereas skin has receptors for detecting touch, pressure, heat (or cold) and pain, etc. The common type of receptors also have special names such as photoreceptors, phonoreceptors, olfactory receptors, gustatory receptors and thermoreceptors.

Photoreceptors detect light (they are present in eyes), phonoreceptors detect sound (they are present in inner ears), olfactory receptors detect smell (they are present in nose), gustatory receptors detect taste (they are present in tongue) whereas thermoreceptors detect heat or cold (they are present in skin).

A stimulus is a kind of energy such as light, sound, smell, taste, heat, or mechanical pressure, etc. Receptors contain groups of cells which are sensitive to the energy provided by the stimulus. At a receptor, the energy provided by a stimulus sets off a chemical reaction which converts the energy of stimulus into an electrical signal called ‘electrical impulse’ (nerve impulse or just impulse).

So, all the receptors in the sense organs receive stimuli from the surrounding environment and send the message conveyed by them to the spinal cord and brain in the form of electrical impulses through the sensory nerves. Another type of nerves called motor nerves transmit the response from the brain and spinal cord to the ´effectors’, again in the form of electrical impulses. An effector is a part of the body which can respond to a stimulus according to the instructions sent from the nervous system (spinal cord and brain).

The effectors are mainly the muscles and glands of our body. All our muscles and glands respond to electrical impulses sent from the nervous system through motor nerves.

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination in Humans

There are two systems of coordination of activities in humans. These are :

•  Nervous system, and
•  Endocrine system (or Hormonal system).
  In human beings, nervous system and endocrine system work together to control and coordinate all our activities such as our physical actions, our thinking processes and our emotional behaviour. Both the systems of coordination, nervous system and endocrine system, consist of a number of organs working together in a systematic way. We will now describe the nervous system and endocrine system in humans in detail, one by one. Let us discuss the nervous system first.

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination  Human Nervous System

The function of nervous system is to coordinate the activities of our body. It is the control system for all our actions, thinking and behaviour. The nervous system helps all other systems of our body to work together. The nervous system is like a manager inside our body. Its job is to control and coordinate the parts of our body so that they work together, doing their job at the right time. Our nervous system coordinates muscles so that we can do things which need thinking like reading, writing, cycling or dancing.

The nervous system also coordinates things which we don’t have to think about, like heart beat and breathing. The human nervous system receives information from the surroundings, processes it, interprets it and then responds accordingly. The nervous system also passes information from one internal system to another. For example, as soon as we put food in our mouth, it immediately causes the release of saliva from the salivary glands.

The Unit of Nervous System : Neuron

The units which make up the nervous system are called nerve cells or neurons. So, neuron is the structural and functional unit of the nervous system. We can now say that nervous system is made of special cells called neurons. Neuron is the largest cell in the body (which looks like an electric wire).

Neurons contain the same basic parts as any other animal cell but their structure is specially adapted to be able to carry messages over large distances in the body quickly. The neurons carry messages in the form of electrical  signals called electrical impulses or nerve impulses.

A neuron (or nerve cell) has three components :

•  Cell body,
•  Dendrites, and
• Axon.

The cell body of a neuron is like a typical animal cell which contains cytoplasm and a nucleus . A number of long and thin fibres are stretching out from the cell body of a neuron. They are called nerve fibres. The shorter fibres on the body of a neuron are called dendrites. The longest fibre on the cell body of a neuron is called axon. The axon has an insulating and protective sheath (or cover) of myelin around it (Myelin is made of fat and protein). It is clear that both dendrites and axon arise from the cell body of a neuron.

The messages which the neurons transmit in the nervous system are in the form of electrical impulses called nerve impulses (or just impulses). The dendrites pick up the nerve impulses (or messages) from receptors. They pass the impulses to the cell body and then along the axon. The axon passes the impulse (or message) to another neuron through a junction called synapse. Neurons are of three types : sensory neurons, motor neurons and relay neurons.

• Sensory neurons transmit impulses from the sensory cells (or receptors) towards the central nervous system (spinal cord and brain).
•  Motor neurons transmit impulses from the central nervous system (spinal cord and brain) towards the muscle cells (or effectors).
•  Relay neurons occur in the central nervous system (brain and spinal cord) where they serve as links between other neurons.

We will now explain how nerve impulses (or messages) are transferred from one neuron to another in the nervous system. Any two neurons in the nervous system do not join to one another completely. There is always a very, very small gap between the two neurons (where they join). This gap is called a synapse. The nerve impulses are carried over this small gap between a pair of neurons by means of a chemical substance called neurotransmitter substance.

We can now say that : A microscopic gap between a pair of adjacent neurons over which nerve impulses pass when going from one neuron to the next is called a synapse. Thus, synapses connect neurons (though it looks surprising that even gaps can connect two things !). We will now understand the conduction of electrical nerve impulses through synapse with the help of a diagram. Suppose there are two neurous (or nerve cells) A and B near each other .

Let A be a sensory neuron which is directly connected to the receptor. There is an extremely small, microscopic gap between the end of the axon of neuron A and the dendrite of the next neuron B which is called a synapse . We will now explain how the electrical impulse travels through the gap (synapse) between the two neurons. The receptor in a sense organ is in touch with the dendrites of sensory neuron. When a stimulus acts on the receptor, a chemical reaction is set off which produces an electrical impulse in it.

This impulse travels from the dendrite of sensory neuron A to its cell body and then along its axon. At the end of axon of sensory neuron A, the electrical impulse releases tiny amount of a chemical substance into the synapse (or gap). This chemical substance crosses the gap (or synapse) and starts a similar electrical impulse in the dendrite of the next neuron B. From the dendrite, this

electrical impulse is carried to the cell body and then to the end of axon of the second neuron. It can then be transferred to a third neuron in a similar way. This process goes on till the electrical impulse reaches the relay neurons in spinal cord and brain. The relay neurons and motor neurons connect in a similar way to bring electrical impulses from the brain and spinal cord to the effectors like muscles and glands. Synapses actually act like one-way valves.

This is because the chemical substance is present on only one side of the gap. Due to this, the nerve impulses (or messages) through a particular set of neurons can go across only from one side (which contains the chemical substance). In this way, synapses ensure that
nerve impulses travel in only one direction (through a particular set of neurons).

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination The Organs Of Human Nervous System

The main organs of the nervous system are: Brain, Spinal cord and Nerves. The sense organs like eyes, ears, tongue, nose and skin can be considered to be other organs of the nervous system because they help in the functioning of the nervous system. The main organs of the nervous system are shown in . The brain is located inside the skull of our head. The spinal cord is a very thick nerve which runs inside the cavity of backbone in our body.

The upper end of spinal cord is attached to the brain. The nerves are a kind of wires which are distributed all over our body. The brain and spinal cord are connected to all the sense organs and other parts of our body by millions of nerves. There are mainly two types of nerves in our body : cranial nerves and spinal nerves. The cranial nerves connect all the parts in the head directly to brain. The spinal nerves connect all the remaining parts of the body (like muscles and skin, etc.) to the spinal cord .

There is also a third type of nerves called visceral nerves. Most of the visceral nerves connect the internal organs of the body to spinal cord though some also connect to brain (Visceral nerves have not been shown in to keep the diagram simple and avoid confusion). The cranial nerves, spinal nerves and visceral nerves are also of two types : sensory nerves and motor

This is how the nervous system works : When the sense organ (like eyes, ears, tongue, nose, or skin) in our body is affected, it sends the message to the brain in the form of electrical impulses (called nerve impulses) through the sensory neurons. The brain analyses this message and decides the action to be taken. The brain then sends out instructions to the muscles of the concerned body part (for taking necessary action) through motor nerves. The concerned body part then acts according to the instructions sent by the brain.

Please note that in the processing of complicated responses (which require thinking) both, the brain and spinal cord are involved, but in the simple responses (which do not require thinking), the spinal cord alone is involved.

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination The Parts of the Nervous System

The nervous system can be divided into two main parts :

1. Central nervous system (consisting of brain and spinal cord), and

2. Peripheral nervous system (consisting of all the nerves of the body like cranial nerves, spinal nerves and visceral nerves). The peripheral nervous system can be further divided into two parts:

• Voluntary nervous system (which is under voluntary control from the brain), and
• Autonomic nervous system (which operates automatically or involuntarily).

The classification of nervous system into various parts is given in the following chart:

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination The Pheripheral Nervous System

All the nerves of the body together make up the peripheral nervous system (PNS). They all enter or leave the central nervous system. The three types of nerves which make up the peripheral nervous system are spinal nerves, cranial nerves and visceral nerves. Spinal nerves arise from the spinal cord along most of the length of the spinal cord and spread throughout the body (except the head). They all carry both sensory and motor neurons and are described as mixed nerves.

Cranial nerves arise from the brain and spread throughout the head. They also carry both sensory and motor neurons. The visceral nerves are a special kind of nerves which mostly arise from the spinal cord (though some also arise from the brain). They are connected to the internal organs of the body. Visceral nerves also carry both sensory and motor neurons.

KSEEB Class 10 SSLC Biology Chapter 2 Control And Coordination Reflex Action And Reflex Arcs

The simplest form of response in the nervous system is reflex action. This is a rapid, automatic response to a stimulus which is not under the voluntary control of the brain. It is described as an involuntary action. Thus, a reflex action is one which we perform automatically. It is a comparatively simple form of behaviour in which the same stimulus produces the same response every time. If we unknowingly touch a hot plate, we immediately move our hand away from it.

So, moving our hand away on touching a hot plate is an example of reflex action. Similarly, moving our foot away when we step on something sharp, is also an example of reflex action. A knee jerk, movement of diaphragm (during respiration), coughing, yawning, blinking of eyes and sneezing are all reflex actions. In a reflex action, we are unaware that anything is going to happen to us. Reflex actions are the actions which we do without thinking to protect ourselves.

For example, coughing is a reflex action which clears our windpipe. The pupils of our eyes get smaller in bright light. This reflex action protects the retina of our eyes from damage due to too much light.

The pupils of our eyes get bigger in dim light so as to help us see properly even in dim light. The pathway (or route) taken by nerve impulses in a reflex action is called the reflex arc. Reflex arcs allow rapid response. We will explain the meaning of a reflex arc by taking an example. A reflex action is an automatic response to a stimulus. An example of the way in which we respond to a stimulus is our reaction to touching a hot object (like a hot plate). Very quickly, and without thinking about it, we pull our hand away.

This sort of very fast, automatic response is called the reflex action. Figure 30 shows the pathway taken by the nerve impulses in this reflex action. The stimulus here is the heat which we feel in our hand on touching the hot plate. This heat is sensed by a heat receptor (or thermoreceptor) in our hand. The receptor triggers an impulse in a sensory neuron, which transmits the message to the spinal cord. Here, the impulse is passed on to a relay neuron, which in turn, passes it to a motor neuron.

The motor neuron passes the impulse to a muscle in our arm. The muscle then contracts and pulls our hand away from the hot plate. The muscle of arm is an effector because it responds to the stimulus. This pathway along which the impulse travels is called the reflex arc.

The reflexes of this type which involve only the spinal cord are called spinal reflexes. Though spinal reflexes are produced in the spinal cord but the message of reflex action taken also goes on to reach the brain. Please note that when we lift a hot plate, then alongwith heat, the pain produced by heat also acts as a ‘stimulus’. The reflex arc described in the above example can be shown in the form of a flow-chart given in .

Most of the reflex actions involve only the spinal cord. They are called spinal reflexes. The reflex action which we have shown in is actually a spinal reflex. And the reflex arc given in is actually a spinal reflex arc. Some reflex actions, however, involve the brain rather than the spinal cord. Such reflex actions are known as cerebral reflexes. This is described below.

Those reflex actions which involve brain are called cerebral reflexes. Cerebral reflexes occur in the organs present in the head because these organs are directly connected to the brain. This will become clear from the following example. Our eyes are present in the head. In dim light, the pupil (a hole in the front of eye) is large so that more light can enter into the eye and make us see properly even in dim light .

Now, when a bright light shines into our eye, then the pupil of our eye automatically becomes smaller (and prevents the damage to the retina of eye from too much light) . The contraction of pupil of our eye automatically in the presence of bright light is an example of cerebral reflex. This cerebral reflex action can be explained as follows: When a bright light falls on the eye, the light receptors in the eye produce impulses in the sensory nerves.

The sensory nerves carry this message of bright light in the form of electrical impulses to the brain. The brain produces the response (that the amount of light entering the eye must be reduced). The response produced by the brain is carried by motor nerves to the circular muscles of the iris of the eye. The circular muscles of the iris of the eye contract and reduce the size of the pupil (or hole) of the eye. As the size of pupil becomes smaller, the amount of light entering the eye is reduced. All this happens very, very quickly.

This cerebral reflex action can be shown by drawing a reflex arc given in  Please note that though the pupil is a circular opening (or hole) in the centre of the iris of the eye but it appears to be dark because no light is reflected from it

How the Effectors (or Muscles) Cause Action or Movement

When a motor nerve impulse sent by the spinal cord (or brain) reaches the effector organs (which are muscles), then the muscles cause action or movement (such as lifting the hand away from a hot plate). We will now describe how muscles are able to move in response to electrical nerve impulses and cause action.

Muscles are made up of muscle cells. Muscle cells contain special proteins which can change their arrangement when stimulated by electrical impulses, causing the muscle cells to change shape and contract. When the muscle cells contract, the muscles also contract (and become shorter). When the muscles contract, they pull on the bones of the body part and make it move.

For example, when electrical impulses sent by the spinal cord (or brain) stimulate the biceps muscle of the upper arm, they make biceps muscle to contract. And when the biceps muscle contracts, it pulls on a bone of the lower arm and makes it move (lifting the hand away from the hot plate). Please note that the contraction of muscles (or muscle cells) caused by the action of electrical impulses is a reversible process.

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination The Autonomic Nervous System

The term ‘autos’ means ‘self’ and ‘nomos’ means ‘governing’, so ‘autonomic nervous system’ means ‘self governing nervous system’. The autonomic nervous system is that part of the peripheral nervous system which controls the activities of the organs inside our body automatically even without our thinking about them. The autonomic nervous system is a specific network of nerves in the body which controls the processes like breathing, heart beat, digestion, sweating, etc.,

that maintain our life and keep us alive. The nerves of the autonomic nervous system are attached to the smooth muscles of the various internal organs of the human body like head, heart, blood vessels, alimentary canal, lungs, kidneys, urinary bladder, glands and skin, etc. Thus, the autonomic nervous system controls and regulates the functions of the internal organs of our body involuntarily (on its own).

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination Voluntary Nervous System

Those actions which need thinking and which are performed by us knowingly are called voluntary actions. For example, speaking to a friend, writing a letter, dancing, cycling, kicking a football, standing in a room or sitting on a chair, are all voluntary actions.

The voluntary nervous system helps us take voluntary actions which are under the conscious control of the brain. We will now give an example to understand the working of voluntary nervous system.

Suppose we are walking down to school at a slow pace. After covering some distance, we look at our watch and find that we are getting late. So, we start walking very fast. We can do this because of our voluntary nervous system as follows:

• When our eyes see time on the watch, they send this information to the brain through the sensory nerves.
•  The brain analyses this information and decides that since there is risk of being late to school, so we should walk faster.
• The brain sends the instructions to walk faster to the muscles of our legs through the motor nerves.

The muscles of the legs act accordingly and make us walk faster.

This is an example of voluntary action and the decision to take this voluntary action has been made by the voluntary nervous system.

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination Central Nervouse System

The central nervous system (CNS) consists of the brain and the spinal cord. Like a telephone exchange with ingoing and outgoing wires, it is responsible for the coordination and control of the activity of the nervous system.

The work of central nervous system is to direct incoming messages to the motor neurons that are connected to the part of the body which will respond to a stimulus. In complicated responses, the brain and spinal cord are both involved. That is, in complicated responses, central nervous system is involved. The central nervous system enables a person to give a more appropriate and more intelligent response to various situations.

By using the central nervous system, a person can vary his behaviour according to the changing situations. This point will become more clear from the following example. If we pick up a very hot plate in the kitchen (without knowing that it is very hot), then our reflex action produced by the spinal cord alone says that we should pull away our hand (so that our hand is saved from burns). But if we pull away our hand, then the plate would drop and break into pieces (and our mother will definitely scold us for breaking the plate!).

Now, it is here that the central nervous system involving brain steps in. When the message from our fingers saying that the ‘plate is too hot’ arrives at our central nervous system, there is already another message saying ‘but don’t drop it’ (This is due to the intelligence of the brain). The central nervous system will consider the two messages together. It may then decide to send a message to our muscles to tell them to put down the plate gently and not drop it.

This intelligent response has been made possible only due to the central nervous system. The job of the central nervous system is to collect all the information from all the receptors in our body. This information is added together before messages are sent out to the effectors. In this way, the best action can be taken in a particular set of circumstances. We will now describe the two organs of the central nervous system, brain and spinal cord in detail.

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination Brain

Brain is the highest coordinating centre in the body. The brain is located inside the skull of our body (at the top of the spinal cord). It is protected by a bony box in the skull called cranium  The brain is surrounded by three membranes called meninges, which help to protect it. The space between the membranes (or meninges) is filled with a cerebro spinal fluid which protects the brain from mechanical shocks. Pairs of cranial nerves arise from the brain.

The brain is broadly divided into three regions forebrain, midbrain and hindbrain. The forebrain consists mainly of cerebrum. The midbrain does not have any further divisions. The hindbrain consists of three centres called pons, cerebellum and medulla. We will now discuss the functions of the forebrain, midbrain and hindbrain. Let us start with cerebrum which is in the forebrain.

The cerebrum (or forebrain) is the main thinking part of the brain. It is the site of our faculties such as learning, reasoning, intelligence, personality and memory. All our thoughts, sensations, actions and movements are controlled by the cerebrum. The cerebrum has different areas for performing different functions. There are association areas in cerebrum which control thinking and

memory. These association areas also store information and experiences. There are sensory areas where information is received from the sense organs like eyes, ears, nose, tongue and skin, and give us the ‘sensation’ or ‘feeling’. Similarly, cerebrum has motor areas from which instructions are sent to muscles to do various types of jobs.

All the voluntary actions of the body are coordinated by the cerebrum. This happens as follows: The cerebrum receives sensory information through the receptors of sense organs. The cerebrum interprets this information in the light of previous experiences and takes a decision which it thinks is right. It then sends out instructions to the motor area (which controls the movement of voluntary muscles) so as to make voluntary muscles move to bring about the appropriate responses.

We will now describe the functions of midbrain. The midbrain controls reflex movements of the head, neck and trunk in response to visual and auditory stimuli. It also controls the reflex movements of the eye muscles, changes in pupil size and shape of the eye lens. We will now describe the functions of the parts of the hindbrain which are pons, cerebellum and medulla. The pons takes part in regulating respiration. The cerebellum helps in maintaining posture and balance of the body.

It also enables us to make precise and accurate movements. The cerebellum coordinates smooth body movements such as walking, dancing, riding a bicycle and picking up a pencil, etc. Medulla controls various involuntary actions such as heart beat (blood circulation), breathing, blood pressure and peristaltic movements of alimentary canal. Medulla is also the controlling centre for reflexes such as swallowing, coughing, sneezing, secretion of saliva and vomiting.

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination Spinal Cord

Spinal cord is a cylindrical structure. The spinal cord begins in continuation with medulla and extends downwards. It is enclosed in a bony cage called vertebral column. Spinal cord is also surrounded by membranes called meninges. As many as 31 pairs of nerves arise from the spinal cord . The spinal cord is concerned with spinal reflex actions and the conduction of nerve impulses to and from the brain.

Before we end this discussion, we would like to give the various functions of brain. The various functions of brain are as follows:

• The brain receives information-carrying nerve impulses from all the sensory organs of the body.

•  The brain responds to the impulses brought in by sensory organs by sending its own instructions (through motor nerves) to the muscles and glands causing them to function accordingly.
•  The brain correlates the various stimuli from different sense organs and produces the most appropriate and intelligent response.
• The brain coordinates the body activities so that the mechanisms and chemical reactions of the body work together efficiently.
•  The brain stores ‘information’ so that behaviour can be modified according to the past experience. This function makes the brain the organ of thought and intelligence.

Before we describe the hormonal system or endocrine system for the coordination in human beings, we should know the meanings of two terms: hormones and endocrine glands. So, let us first discuss hormones and endocrine glands.

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination Hormones

Hormones are chemical substances secreted in very small amounts by specialised tissues in the body called endocrine glands. These hormones coordinate the activities of living organisms and also their growth. So, we can now say that: Hormones are the chemical substances which coordinate the activities of living organisms and also their growth. Hormones are made inside the body of an organism in very small amounts. The various characteristics of hormones are given below :

•  The hormones are secreted in small amounts by the endocrine glands.
•  The hormones are poured directly into the blood and carried throughout the body by blood circulatory system.
•  The hormones have their effect at the sites different from the sites where they are made. So, they are also called chemical messengers.
•  The hormones act on specific tissues or organs (called target organs).

The hormones coordinate the activities of the body and also its growth.

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination Endocrine Glands

A gland is a structure which secretes a specific substance (or substances) in the body. A gland is made up of a group of cells or tissue. There are two types of glands in the body :

1. Exocrine glands, and
2. Endocrine glands.

A gland which secretes its product into a duct (or tube) is called an exocrine gland. For example, the salivary gland secretes the saliva into a duct called salivary duct, therefore, salivary gland is an exocrine gland. Thus, exocrine glands are the glands having ducts ). A gland which does not have a duct and secretes its product directly into the blood stream is called an endocrine gland. Thus, endocrine glands are ductless glands. An endocrine gland secretes a chemical substance called hormone.

We can now say that : A structure (group of cells or tissue) which makes hormones in the body is called an endocrine gland. The various endocrine glands present in the human body are shown in The endocrine glands do not have ducts to secrete their hormones, so they are also called ductless glands. The endocrine glands release hormones directly into the blood of a person. These hormones reach the concerned body part through the blood and act on it.

Hormones are a kind of chemical messengers. A hormone is produced in one part of the body but it acts on some other part of the body. The hormones are of different types and perform different functions.

Some of the glands in our body have both exocrine and endocrine functions. The pancreas, testes and ovary are such glands. For example, pancreas acts as an endocrine gland and secretes the hormone insulin. It also acts as an exocrine gland and secretes pancreatic juice containing digestive enzymes into the pancreatic duct that leads to the alimentary canal. The testes are glands which act as endocrine glands and secrete the hormone called testosterone.

They act as exocrine glands and release sperms (male sex cells) into the duct. Similarly, ovaries are glands which act as endocrine glands and secrete the hormones oestrogen (read as ‘estrogen’) and progesterone. They act as exocrine glands and release ova or eggs (female sex cells) into the duct.

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination The Endocrine System

A group of endocrine glands which produces various hormones is called an endocrine system. The endocrine system is also called hormonal system. We will now discuss the endocrine system in humans in detail.

In addition to nervous system, the endocrine system also helps in coordinating the activities of our body. The endocrine system in our body consists of a number of glands (or tissues) which make, store, and release chemicals called hormones.

There are a large number of endocrine glands in the human body. The endocrine glands present in the human body are: Pineal gland; Hypothalamus gland; Pituitary gland ; Thyroid gland; Parathyroid glands; Thymus ; Pancreas ; Adrenal glands ; Testes (only in males) and Ovaries (only in females). The positions of all these endocrine glands in the human body are shown in . The endocrine glands are located in different parts of the body. As we can see from , the endocrine glands are located in the head, neck and trunk of our body.

Different endocrine glands make different types of hormones which act on different organs of our body. The working of endocrine glands is controlled by our nervous system. The hormones produced by endocrine glands act as messengers between the nervous system and the organs of our body. We will now take the example of adrenal glands to show how the endocrine system (or hormonal system) coordinates our body activities.

There are two adrenal glands in our body, one on top of each kidney . The adrenal glands make adrenaline hormone. The adrenaline hormone prepares our body to function at maximum efficiency during emergency situations like danger, anger, excitement, etc.

This happens as follows: When we are faced with a dangerous situation (like being chased by a ferocious dog), then our nervous system stimulates the adrenal glands to secrete more adrenaline hormone into our blood. This adrenaline hormone increases our ‘heart beats’, ‘breathing rate’, ‘blood flow into muscles’ and causes liver ‘to put more stored glucose into our blood’.

All these actions of adrenaline hormone produce a lot of energy in our body very, very quickly. And this energy helps us to run away very fast from the dog to save ourselves. In this way, the adrenaline hormone prepares our body to run away very fast from a frightening object. Similarly, it is the adrenaline hormone which prepares our body to fight an enemy (say, a burglar in our house) by providing us a lot of energy in a very short time.

A lot of adrenaline hormone is also secreted by adrenal glands when we are ‘angry’ or ‘excited’. The rapid output of energy thus caused helps us to cope with these extreme emotional situations.

The complete coordination in the human body is achieved by the nervous system and endocrine system working together. The main centres in the body for the coordination of the two systems of control (nervous system and the endocrine system) are the hypothalamus and pituitary gland. The hypothalamus plays an important role in collecting information from other regions of the brain and from blood vessels passing through it.

This information is passed on to pituitary gland which by its own secretions, directly or indirectly, regulates the activities of all other endocrine glands. The hormones are involved in the regulation of several functions in the human body like growth, metabolic activities and reproduction. We will now give the names of the endocrine glands, the hormones released by these glands, and the functions of these hormones in the human body.

Please note that pineal gland which is present in the brain has no known function. Pineal gland is supposed to be a vestigial organ (Vestigial organs are those organs which no longer function). Let us discuss the other endocrine glands now.

1. Hypothalamus

Hypothalamus gland is present in the brain. Hypothalamus produces ‘releasing hormones’ and ‘inhibitory hormones’. The function of hypothalamus is to regulate the secretions of hormones from pituitary gland. That is, hypothalamus controls the pituitary hormones.

2. Pituitary Gland

Pituitary gland is present just below the brain. The pituitary gland secretes a number of hormones. One of the hormones secreted by pituitary gland is growth hormone (or human growth hormone). The growth hormone controls the growth of the human body. For example, growth hormone controls the development of bones and muscles. A person having a deficiency of growth hormone in childhood remains very short and becomes a dwarf. On the other hand, a person having too much growth hormone becomes verv tall (or a giant) .

3. Thyroid Gland

Thyroid gland is attached to the wind pipe in our body. Thyroid gland makes a hormone called thyroxine (which contains iodine). The function of thyroxine hormone is to control the rate of metabolism of carbohydrates, fats and proteins in the body. Iodine is necessary for the making of thyroxine hormone by thyroid gland, therefore, a deficiency of iodine in the diet can cause a deficiency of thyroxine hormone in the body.

The deficiency of iodine in the diet of a person produces less thyroxine hormone and causes a disease known as goitre. The main symptom of goitre is that the neck of the person appears to be swollen (due to the enlargement of thyroid gland located in the neck). People are advised to use iodised salt for cooking food so as to prevent goitre disease. This can be explained as follows: Iodine is required by the thyroid gland to make thyroxine hormone.

Iodised salt contains appropriate amount of iodine compounds (such as potassium iodide). Iodised salt can provide all the iodine needed by thyroid gland to make sufficient thyroxine for our body . Since there will be no deficiency of thyroxine in the body, goitre cannot develop.

4. Parathyroid Glands

There are four small parathyroid glands which are embedded in the thyroid gland . Parathyroid glands secrete a hormone called parathormone. The function of parathormone hormone is to regulate calcium and phosphate levels in the blood.

5. Thymus Gland

Thymus gland lies in the lower part of the neck and upper part of chest. Thymus gland secretes thymus hormone which plays a role in the development of the immune system of the body. Thymus gland is large in young children but shrinks after puberty (or sexual maturity).

6. Pancreas

The pancreas is just below the stomach in the body. Pancreas secretes the hormone called insulin. The function of insulin hormone is to lower the blood sugar level (or blood glucose level). Deficiency of insulin hormone in the body causes a disease known as diabetes. Diabetes disease is characterised by large quantities of sugar in the blood (and even urine). The insulin hormone controls the metabolism of sugar.

If, due to some reason, pancreas does not produce and secrete sufficient amount of insulin into blood, then the sugar level in the blood rises. The high sugar level in the blood can cause many harmful effects to the body of a person. The person having high sugar level in blood (or diabetes) is called a diabetic. Diabetic

persons are advised by doctors to take less sugar in their diet. Common diabetes can be controlled by controlling diet, reducing weight, doing regular physical exercise and taking medicines. The persons having severe diabetes are treated by giving injections of insulin.

7. Adrenal Glands

There are two adrenal glands which are located on the top of two kidneys. The adrenal glands secrete adrenaline hormone. The function of adrenaline hormone is to regulate heart rate, breathing rate, blood pressure and carbohydrate metabolism. Adrenaline hormone is secreted in small amounts all the time but in large amounts when a person is frightened or excited. When adrenaline is secreted in large amounts it prepares our body for action.

It speeds up heart beat and breathing, raises blood pressure and allows more glucose (carbohydrate) to go into the blood to give us a lot of energy quickly to fight or flight (run away). Adrenal glands are often called ‘glands of emergency’.

8. Testes

Testes are the glands which are present only in males (men). Testes make male sex hormones called testosterone. The function of testosterone hormone is to control the development of male sex organs and male features such as deeper voice, moustache, beard, and more body hair (than females). All these changes caused by testosterone are associated with male puberty which the boys attain at an age of 13 to 14 years. The testes also make the male gametes called sperms.

9. Ovaries

Ovaries are the glands which are present only in females (women). Ovaries make two female sex hormones called oestrogen and progesterone. The function of oestrogen hormone is to control the development of female sex organs, and female features such as feminine voice, soft skin and mammary glands (breasts).

All these changes caused by oestrogen are associated with female puberty which the girls attain at an age of 10 to 12 years. The function of progesterone hormone is to control the uterus changes in menstrual cycle. It also helps in the maintenance of pregnancy. The ovaries also make the female gametes called ova (or eggs).

KSEEB Class 10 SSLC Biology Chapter 2 Control and Coordination Feedback Mechanism

The excess or deficiency of hormones has a harmful effect on our body. For example, the deficiency of insulin hormone results in a disease called diabetes whereas excess of insulin in the body can lead to coma. So, it is necessary that the hormones are secreted by the glands in our body in precise quantities which are required for the normal functioning of the body. This means that there should be some ‘mechanism’ to regulate the production and release of hormones in the body.

The timing and amount of hormones released by various glands are controlled by the ‘feedback mechanism’ which is in-built in our body. For example, if the sugar level in the blood rises too much, they are detected by the cells of pancreas which respond by producing and secreting more insulin into blood. And as the blood sugar falls to a certain level, the secretion of insulin is reduced automatically.

Before we end this discussion we would like to give a comparison of the nervous system and endocrine system (or hormonal system) for the control and coordination in humans (and other higher animals).

KSEEB Class 10 SSLC Sociology Chapter 4 Social Problems Notes

• Social problems are universal occurrences. There is no society in the world which is free from problems.
• The presence of a problem in a society is a sign of its malaise.
• The societies of the developing countries are afflicted with many problems i.e., excessive population, poverty, unemployment, beggary, juvenile delinquency, crimes, problems of children labour, corruption, exploitation of women, dowry harassment and disturbed youth.
• According to the Constitution, “Child labourers are those who are aged below 14 years and work in order to earn money.”
• Majority of the child labourers work in rural areas such as fields, farms and plantations. The rest works in urban and industrial areas.
• Child labour is the result of a serious lacuna in the social system.
• The government has decided to take certain measures to free children from employment and exploitation and to rehabilitate them.
• ‘Rehabilitation Welfare Fund of Child Labourers’ is launched by the Central Government providing various facilities and stopping the exploitation of the children.
• The ‘Child Labour Prohibition and Control Act (1986) has been passed to prohibit the appointment of child labourers.
• Industrialists who violate this law will have to mandatorily contribute 20,000 per child labourer to the welfare fund.

• Article 24 of our Constitution declares that employing children below 14 years for work is a cognizable offence.
• The government had undertaken many measures to eradicate child labour, e.g., the National Child Labour Project’ (NCLP) in 1988; ‘Child Labour Eradication and Rehabilitation Act’ in 2006.
• One of the innumerable problems being faced by Indian women is harassment.
• Rape, violence, suppression, dowry harassment, physical and mental harassment, forced abortions, use of vulgar language, etc., are some of the harassments on women both inside and outside the houses.
• In the name of dowry, women are being abused and subjected to violence, torture and murder.
• Giving or receiving dowry is a punishable crime.
• Dowry diminishes a woman’s self-respect, dignity and stature.
• In order to escape from the dowry menace, people are resorting to child marriage, female feticide and female infanticide.
• To eradicate the dowry system, the Central Government has passed an Act called Prohibition of Dowry Act’ in 1961.
• This Act was amended in 1986.

KSEEB Class 10 SSLC Business Studies Chapter 4 Consumer Education and Protection Consumer Rights

Meaning of the User and the Provider

• The person who uses the goods and services is called “User”.
• The person who supplies goods and services is called “Provider”.

AWARE: Association of Women Against Rising Expenses.

•  Teleshopping : Ordering for the goods through Internet, SMS (short message service) or telephone and paying after receiving the goods at door is called teleshopping.
•  Consumer : Consumer is a person who buys goods or hires or avails services for a consideration called price or wages.
•  Consumer Protection: To protect the consumers against the exploitation by the procedures and traders.

Consumer Rights: They are as follows:

• The right to information about the quality, quantity, purity and standard of the goods.
• The right to be heard the interests with due consideration.
• Right to consumer education to aware about their rights.
• Right to health environment to lead a quality life.
• Right to protest against the marketing of goods which are hazardous to life and property of the consumers.

Precautionary measures while buying goods and services:

• Check the brand of the product.
• Check the quality of the product.
• Check the actual quantity of the product.
• Check the seal (if possible) of the product.
• Check the ingredient used in the product.
• Consumer Education: Education of consumer or consumer education refers to the awareness of the consumer for their rights.

Consumer Protection Act and Consumer Disputes Redressal Agencies Many steps have been taken by the government to protect the rights of consumer so Consumer Production Act 1986 is a significant step in this direction.

This Act safeguards the interests of the consumers and tries to strives their exploitation.

Objectives of Consumer Production Act:

• Accords importance for safety and quality.
• Avoiding production and sale of hazardous goods.
• Supervising on quality, weights, measures and price.
• Compensating the consumer in case of any problem arising as a result of trade.
• Creating awareness to the consumers through consumer education.
• Consumer Protection Act extends to the whole of India except Jammu and Kashmir. World Consumers’ Day is celebrated on 15 March, every year.
• Consumer Disputes Redressal Agencies: The Consumer Protection Act provides for the establishment of a three tier consumer disputes redressal agencies:
• District forum
• State commission
• National commission

Name of the Agency

•  District forum
•  State commission
• National
  commission
  Composition
  Value of goods
  Two members with atleast one woman Complaints entertain when the value of appointed by the state government.
  goods or services is less than 20 lakhs.
  Three members with atleast one woman, one Complaints entertain when the value of is or has been a high court judge.
  goods or services is more than 20 lakhs but less than one crore.
  Headed by a Judge of supreme court and four Complaints entertain when the value of other members with atleast one woman. goods or services is more than one crore.
  Methods to be followed to file a case in consumer court:
• Complaint may be typed or handwritten as there is no prescribed pro forma to file a case.
• Complaint should include the name of the complainer, full address and contact member.
• The person or organization against whom the complaint is made should be mentioned clearly with address.
•  The actual loss of goods should be properly mentioned. Bill or receipt should be enclosed.
• There is no fees or stamp duty for the complaint.
• No advocate or lawyer is resuited. The consumer himself/herself can argue.
  Methods to be followed to file a case in consumer court:
• Complaint may be typed or handwritten as there is no prescribed pro forma to file a case.
• Complaint should include the name of the complainer, full address and contact member.
•  The person or organization against whom the complaint is made should be mentioned clearly with address.
• The actual loss of goods should be properly mentioned. Bill or receipt should be enclosed.
• There is no fees or stamp duty for the complaint.
•  No advocate or lawyer is resuited. The consumer himself/herself can argue.

KSEEB SSLC Class 10 Social Science Notes History

• Chapter 1 Advent of Europeans to India Notes
• Chapter 2 The Extension of the British Rule Notes
• Chapter 3 The Impact of British Rule in India Notes
• Chapter 4 Opposition to British Rule in Karnataka Notes
• Chapter 5 Social and Religious Reformation Movements Notes
• Chapter 6 The First War of Indian Independence (1857) Notes
• Chapter 7 Freedom Movement Notes
• Chapter 8 Era of Gandhi and National Movement Notes
• Chapter 9 Post Independent India Notes
• Chapter 10 The Political Developments of 20th Century Notes

KSEEB SSLC Class 10 Social Science Notes Political Science

• Chapter 1 The Problems of India and their Notes
• Chapter 2 Indian Foreign Policy Notes
• Chapter 3 India’s Relationship with Other Countries Notes
• Chapter 4 Global Problems and India’s Role Notes
• Chapter 5 International Institutions Notes

KSEEB SSLC Class 10 Social Science Notes Sociology

• Chapter 1 Social Stratification Notes
• Chapter 2 Labour Notes
• Chapter 3 Social Movements Notes
• Chapter 4 Social Problems Notes

KSEEB SSLC Class 10 Social Science Notes Geography

• Chapter 1 Indian Position and Extension Notes
• Chapter 2 Indian Physiography Notes
• Chapter 3 Indian Climate Notes
• Chapter 4 Indian Soils Notes
• Chapter 5 Indian Forest Resources Notes
• Chapter 6 Indian Water Resources Notes
• Chapter 7 Indian Land Resources Notes
• Chapter 8 Indian Mineral & Power Resources Notes
• Chapter 9 Indian Transport and Communication Notes
• Chapter 10 Indian Industries Notes
• Chapter 11 Indian Natural Disasters Notes
• Chapter 12 Indian Population Notes

KSEEB SSLC Class 10 Social Science Notes Economics

• Chapter 1 Development Notes
• Chapter 2 Rural Development Notes
• Chapter 3 Money and Credit Notes
• Chapter 4 Public Finance and Budget Notes

KSEEB SSLC Class 10 Social Science Notes Business Studies

• Chapter 1 Bank Transactions Notes
• Chapter 2 Entrepreneurship Notes
• Chapter 3 Globalization of Business Notes

KSEEB Class 10 SSLC Business Studies Chapter 3 Globalization Of Business Globalization

After 1980, globalization achieved a great progress in the economic reforms of developing countries.
Globalization is the growing economic interdependence of countries worldwide through increasing volume and variety of cross border transactions in goods and services, capital movement and through the more rapid and widespread diffusion of technology.

Characteristics of Globalization:

•  Cross border movement of goods and services
•  International flow of capital, technology and information
•  Formation of one world wide market
• Production of goods in any region at cheaper cost.

Factors that are included in Globalization:

• Referring the world wide phenomenon of technical, economic, political and cultural exchanges.
•  Encouraging international capital & trade overcoming the political barriers.
•  Creating free trade zone by removing the export and import duties.
•  Reducing the transportation expenses.
• Creating subsidies to the world wide trade organization.

Features of Globalization:

•  Free movement of goods, services, capital, etc, across the borders.
•  Labour and professionals migration and immigration between different countries.
•  International flow of technology, information and capital.
•  Formation of one worldwide market by obtaining raw material and other resources from cheap markets.
•  Production and marketing of goods in any region of the world at cheaper cost.
•  Economic, social, cultural integration of an economy with different economies of the world.
• Growing number and importance of multinational companies.

Positive Effects of Globalization:

•  Internationalization of goods and services
•  Globalization of technology
•  Capital inflows and foreign direct investments undertake economic transactions across natural boundaries
•  Economic, social, cultural integration
•  Human resource development
•  Economic growth and development of underdeveloped and developing countries
•  Reducing regional and income inequalities
•  Optimum utilization of world resources
• Improve standard of living.

 Negative Effects of Globalization:

•  Sweat shopping
•  Unethical practices in business dealings
• Cut-throat competition
•  Helped terrorists and criminals
• Increasing pollution and garbage
•  Exploitation of III world countries such as child labour and slavery
•  Promotion of junk food consumption
•  Widened economic inequalities
•  Environmental degradation
• Depletion of natural resources
•  Dislodging domestic industries
• Unemployment in developing countries
•  Spread of deadly viral diseases such as AIDS and Cancer

KSEEB Class 10 SSLC Business Studies Chapter 3 Globalization Of Business World Trade Organization

International trade agreements and WTO:

• WTO office is located at Geneva, Switzerland and established on 19 January, 1995.
• 149 countries in the world are the members of WTO.

Objectives of WTO:

•  Improving standard of living
•  Settling trade disputes between member nations
•  Stimulating economic growth and development
• Promoting international peace and business
•  Encouraging good governance
•  Making international trade and relations smooth

Functions of WTO:

•  Bringing into force the trade agreements throughout the world
•  Acting as a dispute settlement body
• Supervising the revised trade agreements
• Ensuring reduction of tariffs in international trade
•  Assistance to underdeveloped nations
• Ensuring optimum utilization of world resources being the international trade under legal frame work
  Note: WTO was formerly known as GATT (General Agreement on Tariff and Trade) before 1995.

KSEEB SSLC Class 9 Biology Notes Karnataka State Syllabus

• Chapter 1 The Fundamental Unit Of Life Notes
• Chapter 2 Tissues Notes
• Chapter 3 Diversity in Living Organisms Notes
• Chapter 4 Why Do We Fall ill Notes
• Chapter 5 Natural Resources Notes
• Chapter 6 Improvement In Food Resources Notes

KSEEB Class 10 Business Studies Chapter 2 Entrepreneurship notes Role And Importance Of Entrepreneurship

• The word entrepreneur is derived from the French word Entreprendre, which means to undertake some activity.
• Entrepreneur is someone who perceives opportunities, organizes resources needed for exploiting the opportunity and exploits it.

Entrepreneurship is a process of an action of an entrepreneur who undertakes the risk of setting up his own venture for perceived rewards by creative opportunities from innovations.

Features of Entrepreneurship:

• An economic activity
• Risk bearing activity
• Organizing function
• Innovative function
• Goal oriented function

Characteristics of an Entrepreneur:

• Creativity
• Dynamism
• Team building
• Problem-solving
• Risk taking
• Commitment
• Innovation
• Leadership
• Achievement motivation
• Goal orientation
• Decision-making

Functions of Entrepreneur :

• Sensing an opportunity
• Converts ideas into reality
• Develops a business plan
• Establishing an enterprise
• Managerial functions
• Decision-making functions
• Expansion, growth and development

Role of an Entrepreneur :

• Promoting capital formation by mobilizing the savings of the people.
• Enhancing innovation to maximize profits.
• Promoting country’s export trade.
• Promoting the development of industries in urban as well as in rural areas.
• Providing people the better quality of products.
• Working for the growth of the economy by enhancing the production volume.
• Increasing the Gross Domestic Product and Per Capita Income of the country.

Importance of Entrepreneurs:

• Entrepreneurs occupy a central position in a market economy and they serve as the ‘Spark Plug’ in the economy’s engine.
• Entrepreneurs mobilize the savings of the people and invest them in productive purpose which help in the production activities that increase the Gross Domestic Product of the country.
• Indirectly they work for the welfare of the country.

KSEEB Class 10 Business Studies Chapter 2 Entrepreneurship Self-Employment Schemes And Promotional Organisations

Government measures for self-employment schemes:

• Setting up of Financial Institutions like IDBI, NABARD, UTI, LIC, SFC, ICGCI, IFCI for promotion of industrialization.
• Establishment of promotional organizations like DIC, SIDC, NSIC, SISI, Industrial Estates, Khadi and Village Industries Corporation etc.
  The self-employed are a backbone of the nation. A person can setup a unit having a vast opportunity to select any form of business which he/she thinks feasible, e.g., advertising agencies, photocopying centres, beauty parlours, etc.
• District Industrial Centres (DIC) provide support for financial managerial marketing, export-assistance and other assistance in setting up, modernizing, revitalizing sick units, diversifying and solving other problems related to the promotion and development of small and medium industries at district levels.

Some Successful Entrepreneurs of India:

•  Dr.Pratap Reddy: Developer of India’s first hospital group “The Apollo Hospitals”.
•  Naresh Goyal: Founder and chairman of India’s largest domestic Airlines “Jet Airways”.
•  Narayan Murtny: One of the founders of “Infosys Technologies Ltd”.
•  Varghese Kurian: Best known as “Father of the white revolution” of India.
•  Dhirubhai Ambani: Founder of Reliance Company.
• Azim Premji: Chairman of Wipro Technologies.
•  Ekta Kapoor: Creative director of “Balaji Telefilms”.
•  Kiran Mazumdar Shah: Chairman and managing director of Biocon Ltd. The largest bio-technology company in India.

KSEEB SSLC Class 9 Biology Notes Karnataka State Syllabus

• Chapter 1 The Fundamental Unit Of Life Notes
• Chapter 2 Tissues Notes
• Chapter 3 Diversity in Living Organisms Notes
• Chapter 4 Why Do We Fall ill Notes
• Chapter 5 Natural Resources Notes
• Chapter 6 Improvement In Food Resources Notes

KSEEB Class 10 SSLC BUSINESS STUDIES Chapter 1 Banking Transactions Notes

Meaning and Characteristics of Banks, Types of Banks and Finance Transactions by Banks and Post Offices

• Meaning of banks
•  Banks are the financial institutions which accept deposits from the public and use the money deposited as investment and agree to return whenever they require in the form of cheques, drafts or in some other forms.
•  The term bank is derived from the Italian word “BANCO” or from the French word “BANQUE”, both means a “BENCH” or money ovhanno table
•  Financial institution: It is a financial institution which deals with money.
•  Form of organization: Bank may be a person, a group of persons, firm or a company,
• Acceptance of deposits and lensing of loans: Bank acts as a custodian of the deposits of the public and also lends loans in the form of overdraft, cash credit etc.
•  Payment and withdrawal: Customer can withdraw their deposits in the form of cheques and drafts etc.
•  Agency and utility functions: Bank acts as an agent of its customers and also provides general utility services like paying the taxes, paying the insurance premium and locker facility etc.
•  Profit and service orientation: Bank makes profit by rendering various services to its customers.
•  Ever increasing functions: Bank can expand and diversify its activities and functions means many other functions can also be performed by the bank like investment in government securities and mutual funds etc.
• Connecting link: Bank acts as an intermediary between depositors and borrowers as the deposited amount of a person is given as a loan to another person.
•  Banking BUSINESS: The main activity of a bank is the creation of credit by accepting deposits and lending loans.

Name identity: A bank is always associated by the word bank, for example – State Bank of India and Union Bank of India. It enables the customers to know in which bank they are dealing with money. Functions of a bank

KSEEB Class 10 Business Studies Chapter 1 Banking Transactions

The banking functions can be categorized in two types:

•  Primary or main functions.
•  Secondary or agency and general utility functions. Primary or main functions
•  Accepting deposits
•  Lending loans
•  Creation of credit
  Secondary or agency and general utility functions.
•  Transfer of funds
•  Collection of cheques, drafts and bills
•  Discounting of commercial bills
•  Issuing letters of credit and guarantees
•  Underwriting and mutual fund services
  Relationship between bankers and customers
•  General Relationship – it includes the following relationship:
•  Primary relationship as a debtor and creditor
•  Subsidiary relationship as a trustee and beneficiary
•  Agent and principal relationship
•  Special Relationship
•  Obligation to honour cheques
•  Obligation to maintain secrecy of accounts
  Services offered by banks
•  Providing debit and credit card to its customers.
•  Providing personal loan on a reasonable interest.
•  Providing home and vehicle loan.
•  Trading of mutual funds for its customers.
•  Providing locker facilities to safe the consumer’s precious items.
•  Providing trust services by issuing letter of credit etc.
•  Providing signature guarantees.
•  Providing e-banking facilities to its customers.
• Banking transactions-banks and post offices
•  Any sort of activity involving in money or exchange of money in an account is considered as bank transaction.
•  Banks keep money of the customers in the form of deposits and money thus collected is lent to the customers who need money as loans. These loans are called bank loans.
• All the banking transactions in India are controlled and regulated by the Reserve Bank of India (RBI). RBI is known as the mother of all the banks or bankers BANK or Central Bank of India.
• The postal department of India also acts as the saving bank as it provides the following financial facilities-
• Saving bank account facility.
• Retail Banking functions of monthly income schemes, recurring deposits, time deposits, money order facility etc.

KSEEB Class 10 Business Studies Chapter 1 Banking Transactions Types Of Banks

• Central Bank or Reserve Bank of India
• Commercial banks
• Industrial development banks
• Land development banks
• Indigenous banks
• Co-operative banks
• Exchange banks

Types of Accounts, Methods to Open them and Advantages of them

KSEEB Class 10 Business Studies Chapter 1 Banking Transactions Types of Bank Accounts

•  Savings Bank Account: limited transactions per day.
•  Current Account: Unlimited number of transactions can be made.
•  Recurring Deposit Account: Fixed amount each time (fixed) has to pay.
•  Term Deposit Account: A fixed amount is deposited for a certain period.
  Procedure to open a Bank Account:
  To avail professional banking service, it is mandatory for every individual to open a bank account.
•  Decide the type of account you want to open.
•  Approach the bank officer to collect the form.
•  Fill up the bank account form or the proposal form.
•  Give reference for opening your bank account.
•  Submit the bank account form fully filled in the bank.
•  Initial deposit to be made.
  Advantages of opening a Bank Account:
•  Safe custody of money.
•  Facility of deposits and withdrawals.
• Easy borrowing of loans and advance.
•  Financial discipline.
•  Safety of money and valuables.
  Major operations provided by a Banker.
•  Provides savings bank facility.
•  Mobilization of deposits for the purpose of lending.
•  No deposits less than 10 are accepted by bank.
•  Collection and payment of cheques, drafts or other instruments drawn in favour of account holder.
•  Withdrawal of money by account holders through Pass-book, Cheques, ATM.
•  Agency functions on behalf of its account holders.
•  Transfer of account between different branches of the bank and closure of the account at the request of account holder.
•  Crediting prescribed rate of interest for each calendar month on the minimum balance of credit of the account of its account holder.
  Note: No interest is paid to the customer on Current Account.

KSEEB SSLC Class 9 Biology Notes Karnataka State Syllabus

• Chapter 1 The Fundamental Unit Of Life Notes
• Chapter 2 Tissues Notes
• Chapter 3 Diversity in Living Organisms Notes
• Chapter 4 Why Do We Fall ill Notes
• Chapter 5 Natural Resources Notes
• Chapter 6 Improvement In Food Resources Notes