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Karnataka Board Class 11 Biology Biomolecules Synopsis

Even though there is a wide diversity in living organisms, all living organisms are made up of the same chemicals.

The elemental composition of living and non-living matter appears similar when analyzed qualitatively.

• Analysis reveals that the relative abundance of carbon and hydrogen concerning other elements is higher in any living organism than in the earth’s crust.
• The most abundant chemical in living organisms is water.
• All the carbon compounds that we get from living tissues can be called “biomolecules”.
• There are thousands of carbon compounds that we get from living tissues. They are called biomolecules.
• Proteins, nucleic acids, and polysaccharides are three types of macromolecules found in living systems.
• Lipids are small molecular weight compounds and are present not only as such but also arranged into structures like cell membranes and other membranes.
• Proteins are polypeptides and polymers of amino acids. s#e Polysaccharides are long chains of sugar-containing different monosaccharides as building blocks,
• Nucleic acids are made of nucleotides.
• Nucleotide has three components-heterocyclic compounds, monosaccharides, and phosphoric acid.
• Biomolecules have a hierarchy of structures-primary, secondary, tertiary, and quaternary.
• All the chemical reactions that occur is called metabolism. The metabolic flow is called the dynamic state of body constituents.
• The most important form of energy currency in living systems is the bond energy in a chemical called adenosine triphosphate (ATP)
• The living process is a constant effort to prevent falling into equilibrium.

Biomolecules Very Short Question And Answers for Class 11

Question 1. Modlcinos are either man-made (i.e. synthetic) or obtained from living organisms like plants, bacteria, animals, etc., and hence the Inttor are called natural products.  Sometimes natural products are chemically altered by man to reduce toxicity or side effects. Write against each of the following whether they were initially obtained as a natural product or as a synthetic chemical.

1. Penicillin
2. Sulfonamide
3. Vitamin C
4. Growth Hormone

Answer:

1. Penicillin-Natural product
2. Sulfonamide-Synthetic chemical
3. Vitamins-Natural product
4. Growth Hormone-Natural products are

Question 2. Select an appropriate chemical bond among the ester bond, glycosidic bond, peptide bond, and hydrogen bond and write against each of the following.

1. Polysaccharide
2. Fat
3. Protein
4. Water

Answer:

1. Polysaccharide -Glycosidic bond
2. Protein- Peptide bond
3. Fat- Ester bond
4. Water- Hydrogen bond

Question 3. Give one example for each of the amino acids, sugars, nucleotides, and fatty acids
Answer:

1. Amino acid – Example: Glycine
2. Sugars – Example: Glucose
3. Nucleotide-  Example: Adenylic acid
4. Fatty acids –  Example: Palmitic acid

Important questions on Biomolecules Class 11 Karnataka Board

Question 4. Explain the Zwitterionic form of an amino acid.
Answer:

1. is a zwitterionic form a neutral form due to equal positive and negative charges.

2. Amino acid contains both acidic (carboxylic acid) and basic (amino group) centers and hence shows both positive and negative charges.

Question 5. What constituents of DIMA are linked by glycosidic bonds?
Answer:

1. Nitrogen base and pentose (deoxy ribose) sugar, are linked by a glycosidic bond.
2. This bond is formed by dehydration.

Question 6. Glycine and Alanino nro dlfforont with ronpoot to ono aubatituont on the α – carbon. What are the other common substituent groups?
Answer:

H and – CH₃ are substituent groups respectively in Glycine and Alanine- at α  -carbon.

Both contain- H, – COOH, and- NH₂ substituent groups common

Question 7. In Starch, Cellulose, Glycogen, and Chitin are polysaccharides found among the following. Choose the one appropriate and write against each.
Answer:

1. Cotton fibre _____________
2. Exoskeleton of cockroach _____________
3. Liver _____________
4. Peeled potato _____________

Answer:

1. Cotton fibre- Cellulose
2. Liver- Glycogen
3. Exoskeleton of cockroach- Chitin
4. Peeled potato- Starch

Question 8. Find out and make a list of proteins used as therapeutic agents. Find other applications of proteins (For example: Cosmetics etc.)
Answer:

Proteins used as therapeutic agents are thrombin, fibrinogen, enkephalins, antigens, antibodies, streptokinase, protein tyrosine kinase, diastase, renin, insulin, oxytocin, vasopressin, etc.

Other applications: Proteins are also used in cosmetics, dairy industries, textile industries, research techniques, etc

Question 9. Draw the structure of the amino acid, alanine
Answer:

Question 10. Attempt titrating an amino acid against a weak base and discover the number of dissociating (ionizable) functional groups in the amino acid.
Answer:

The existence of different ionic forms of amino acids can be easily understood by the titration curves. The number of dissociating functional groups is one in the case of neutral and basic amino acids and two in the case of acidic amino acids.

Question 11. What are gums made of? Is Fevicol different ?
Answer:

Gums are secondary metabolites. It is made up of compounds present in plants, fungi, and microbial cells. Yes, Fevicol is different from gum. It is a synthetic resin made by polymerization manufactured by the esterification of organic compounds.

Question 12. Find out how much cellulose is made by all the plants in the biosphere and compare it with how much paper is manufactured by man and hence what is the consumption of plant material by man annually. What a loss of vegetation!
Answer:

About 100 billion tonnes of cellulose is prepared per year by the plants of the world. The increase in industrialization increased the use of paper. Due to this vegetation is being lost to a great extent.

Question 13. All life forms exhibit “Unity in diversity” – Give reasons.
Answer:

There is a wide diversity of all living organisms but their chemical composition and metabolic reactions appear to be similar. The most abundant chemical in all life forms is water. Living organisms contain more carbon, hydrogen, and oxygen than animate matter

Class 11 Biology Biomolecules question bank

Question 14. What in meant by the tertiary structure of proteins?
Answer:

When a long protein chain of secondary structure is folded upon itself like a hollow woolen ball, It gives rise to a tertiary structure. Tertiary structure is necessary for many biological activities of protein. This gives us a 3 – dimension view of a protein.

Karnataka Board solutions for Class 11 Biology Chapter 9 Biomolecules Short Question And Answers

Question 1. Explain briefly the metabolic basis for ‘living’.
Answer:

1. Metabolic pathways can lead to a more complex structure from a simpler structure.

For example:

• The formation of sucrose from water and CO₂ in the mesophyll. They are called biosynthetic or anabolic pathways.
• Some metabolic pathways may lead to a simpler structure from a complex structure.
  • For example: Glucose becomes lactic acid in our skeletal muscle. They. are called degradative or catabolic pathways.
• Anabolic pathways consume energy. For instance, the assembly of a protein from amino acids requires energy input.
• Catabolic pathways lead to the release of energy. For instance, the glycolytic pathway leads to the formation of lactic acid from glucose and releases energy.
• It consists of 10 metabolic steps.
•  Living organisms have learned to trap the energy liberated during degradation and store it in the form of chemical bonds.
• This stored bond is utilized as and when biosynthetic, osmotic, and mechanical work is performed.
• The most important form of energy currency in living systems is the bond energy in a chemical called Adenosine Triphosphate (ATP).

Question 2. Is rubber a primary metabolite or a secondary metabolite? Write four sentences about rubber.
Answer:

1. Rubber is a secondary metabolite.
2. Metabolic products that do not have identifiable functions in the host organisms are called secondary metabolites.
3. Rubber is produced from the latex of Hevea and Ficus elastica.
4. Latex is produced in a special type of tissue called laticiferous tissue.
5. The tires of vehicles are made from vulcanization rubber.

Question 3. Schematically represent primary, secondary, and tertiary structures of a hypothetical polymer using protein as an example.
Answer:

Primary, Secondary, and Tertiary structures:

Biomolecules Questions For Class 11

Question 4. Comment on the statement “living state is a non-equilibrium steady state to be able to perform work.”
Answer:

• A living organism consists of tens and thousands of chemical compounds called metabolites or biomolecules.
• Biomolecules are present at concentrations characteristic of each of them.
  • For example:  The blood concentration of glucose in a normal healthy individual to 4.5 to 5.0 mm, while that of hormones would be nanograms / m/.
• All living organisms exist in a steady state characterized by concentrations of each of these biomolecules, that are in a metabolic flux.
• Any chemical or physical process moves spontaneously to equilibrium. The steady state is a non-equilibrium state. As per physics, the systems at equilibrium cannot perform work.
• Living organisms work continuously, they can not afford to reach equilibrium. Hence the living state is a non-equilibrium steady state to be able to perform work.
• The living process is a constant effort to present falling into equilibrium, which is achieved by energy input.
• Metabolism provides a mechanism for the production of energy. Hence the living state and metabolism are synonymous. Thus, without metabolism there can not be a living state.

Question 5. The dynamic state of body constituents is a more realistic concept than the fixed concentrations of body constituents at any point in time Elaborate.
Answer:

Living organisms like simple bacterial cells, protozoans, plants or animals contain thousands of organic compounds, the biomolecules.

1. The biomolecules are present in certain concentrations, and ore is expressed as mols /cell or mols /liter, etc.,
2. All the biomolecules have a turnover. It means that they are constantly being changed into some other biomolecules and are also made from some other biomolecules.
3. This breaking and making is through chemical reactions that are called metabolism.
4. Each of the metabolic reactions results in the transformation of biomolecules.

For example – The removal of CO₂ from amino acids makes an amino acid into an amine.

• The majority of these metabolic reactions do not occur in isolation but are always linked to some other reactions.
• It means metabolites are converted into each other in a series of linked reactions called metabolic pathways.
• The metabolic pathways are either linear or circular, they may criss-cross each other. The flow of metabolites through the pathway has a definite rate and direction.
• The metabolite flow is called the dynamic state of body constituents. Interlinked metabolic traffic is very smooth and without a single reported mishap for healthy conditions.
• Every chemical reaction in a metabolic pathway is a catalyzed reaction. There is no uncatalyzed metabolic conversion in living systems.
• Proteins with catalytic power are named enzymes. They hasten the rate of a given metabolic conversion.

Question 6. What are macromolecules? Give examples.
Answer:

• Macro molecules are large-sized biomolecules that have high molecular weight, lower solubility, and complex molecular structure.
• It occurs in the colloidal state.
• Macromolecules are formed by the polymerization of a large number of macromolecules.
• They belong to four classes of organic compounds- carbohydrates, lipids, proteins, and nucleic acids.

Question 7. Proteins have primary structure. If you are given a method to know which amino acid is at either of the two termini (ends) of a protein, can you connect this information to purify or homogeneity of a protein?
Answer:

• The primary structure of protein is based on the number type and order of amino acid present in the chain.
• A protein has a linear structure in which the left end if the line represents the first and the right end represents the last amino acid.
• The number of amino acids in between the two ends determines the purity or homogeneity of proteins.

Question 8. Explain the composition of triglyceride.
Answer:

• The components of triglyceride are a single molecule of glycerol and 3 fatty acids. In glycerol 3 carbon atoms are present along with 30 n groups.
• Fatty acids consist of long-chain hydrocarbons with a carboxylic group at one end.
• Both of them form an ester bond. This bond is saturated when single-bonded carbons are present and unsaturated when double-bonded carbon atoms are present.

Question 9. Can you describe what happens when milk is converted into curd or yogurt, based on your understanding of proteins?
Answer:

• Milk Is converted Into curd or yogurt due to denaturation of proteins.
• The configuration of protein is lost. In denaturation disruption of bonds that maintain secondary and tertiary structure leads to the conversion of globular proteins into fibrous proteins.
• This involves a change in the physical, chemical, and biological properties of protein molecules.

Karnataka Board Class 11 Biology Chapter 9

Question 10. Can you attempt building models of biomolecules using commercially available atomic models (Ball and Stick models)?
Answer:

Yes, models of biomolecules can be prepared using commercially available atomic models.

• Ball and stick models and space-filling models are 3D models that serve to display the structure of chemical products and substances or biomolecules.
• With ball and stick models, the centers of the atoms are connected by straight lines which represent covalent bonds. Double and triple bonds are often represented by springs.
• The bond angles and bond lengths reflect the actual relationship. The space occupied by the atoms is either not represented at all or only denoted essentially by the relative sizes of the sphere.

Long Answers Questions On Biomolecules For Class 11

Question 1. What are secondary metabolites? Enlist them indicating their usefulness to man.
Answer:

Metabolic products that do not have identifiable functions in the host organism are called secondary metabolites. Secondary metabolites are alkaloids, flavonoids, rubber, essential oils, antibiotics, colored pigments, scents, gums, spices, etc. Many of these secondary metabolites are useful to man.

• Pigments  – Example: Carotenoids, Anthocyanins etc.
• Alkaloids –  Example:  Morphine, Codeine etc.
• Terpenoids –  Example: Monoterpenes, Diterpenes etc.
• Essential oils –  Example: Lemon, grass oil etc.
• Toxins – Example: Abrin, Rlcin
• Drugs –  Example: Vlnblastln, Curcumin, etc.
• Polymeric substances – Example:  Rubber, gums, cellulose, etc.

Question 2. What tiro the processes used to analyze the elemental composition, organic constituents, and inorganic constituents of living tissue? What are the inferences on the most abundant constituents of living tissue? Support the inferences with appropriate data.
Answer:

To analyze elemental composition, organic constituents, and inorganic constituents of living tissue one has to perform chemical analysis.

Analyse Organic Compounds:

• Take any living tissue (a vegetable or a piece of liver etc) and grind it in trichloro acetic acid (Cif. COOH) using a motor and a pestle.
• We obtain a thick slurry.
• If we were to strain this slurry through a cheesecloth or cotton, we would obtain two fractions.
• One is called the filtrate or acid soluble pool and the other is retentate or acid insoluble fraction.
• To identify a particular compound, one has to use various separation techniques and separate an organic compound from the rest.
• Analytical techniques when applied to the compound give us the molecular formula and probable structure of the compound.
• All the carbon compounds that we get from living tissues can be called biomolecules.

Analyse inorganic compounds:

• One weighs a small amount of a living tissue (say a leaf or liver and this is called wet weight) and dry it.
• All the water evaporates.
• The remaining material gives dry weight.
• Now if the tissue is fully burnt, all the carbon compounds are oxidised to gaseous form and are removed.
• The remaining is called ash.
• This ash contains inorganic elements like calcium, magnesium, etc.
• Inorganic elements are also in acid solution fraction.

Elemental analysis:

• The elemental analysis gives the elemental composition of living tissues in the form of hydrogen, oxygen chlorine, carbon, etc.
• Analysis of compounds gives an idea of the kind of organic and inorganic compounds.

Question 3. Nucleic acids exhibit a secondary structure. Describe through Watson Crick Model.
Answer:

• Nucleic acid exhibits a wide variety of secondary structures.
• For example, one of the secondary structures exhibited by DNA is the famous Watson-Crick Model.
• According to this model, DNA exists as a double helix. The two strands of polynucleotides are anti-parallel i.e., run in the opposite direction.
• The backbone is formed by the sugar-phosphate sugar chain.
• The nitrogen bases are projected more or less perpendicular to the backbone but face inside.
• Adenine (A) and Guanine (G) of one strand pair with Thymine (T) and Cytosine (C) respectively, on the other strand. Each step is represented by a pair.
• Coiling occurs at an angle of 360°. At each step, the turn is 36°. One full turn of the helical strand involves 10 base pairs.
• The length of each turn is 34 Å
• The distance between the two steps is 3.4Å
• This form of DNA with the above features is called B- DNA

Watson and Crick’s double helix model of DNA:

P = Phosphate, S = Sugar, A = Adenine, T = Thymine, G = Guanine, C = Cytosine

Karnataka Board Biology important questions on Biomolecules

Question 4. What Is the difference between nucleotide and nucleoside? Give two examples of each with their structure.
Answer:

Question 5. Describe various forms of lipids using a few examples.
Answer:

• Lipids are water-insoluble.
• Lipids could be simple fatty acids.
• A fatty acid has a carboxyl group attached to an R-group.
• The R – group could be methyl (-CH₃) or ethyl (- C₂H₅) or a higher number of CH₂ groups (1 carbon to 19 carbons).

For example – Palmitic acid has 16 carbons including carboxyl carbon.

• Arachidonic acid has 20 carbons including carboxyl carbon.
• Fatty acids could be saturated (without double bond) or unsaturated (with one or more C = C double bonds)

Simple lipid Is glycerol which Is trihydroxy propane.

Many lipids have both glycerol and fatty acids. Here the fatty acids are found esterified with glycerol. They are then called monoglycerides, diglycerides, and triglycerides.

Triglyceride (R₁, R₂, R₃ are fatty acids):

• These are also called fats and oils based on melting point.
• Oils have lower melting points

Example: Gingely oil and hence remains as oil in winter.

• Some lipids have phosphorous and a phosphorylated organic compound in them. These are called phospholipids. They are found in cell membranes.
• One example is Lecithin.
• Some tissues especially the neural tissues have lipids with more complex structures.
• If a phosphate group is also found esterified to the sugar, they are called nucleotides.

Examples:  Nucleotides are adenylic acid, thymidylic acid, guanylic acid, uridylic acid arid cytidylic acid.

Question 6. Illustrate a glycosidic, peptide end n phoepho-diostor bond.
Answer:

Glycosidic bond:

In a polysaccharide, the Individual monosaccharides are linked using a glycosidic bond. This bond Is formed by dehydration. This bond is formed between two carbon atoms of two adjacent monosaccharides.

Peptide bond:

In a polypeptide or a protein amino acids, are linked by peptide bonds. These bonds are formed by the reaction between the carboxyl group (- COOH) of one amino acid with the amino group (NH₂) of the next amino acid, with the elimination of water.

Phospho-diester bond:

In a nucleic acid a phosphate moiety links the 3′ – carbon of one sugar of one nucleotide to the 5′ carbon of sugar of the succeeding nucleotide. The bond between the phosphate and hydroxyl group of sugar is an ester bond. As there is one such ester bond on either side, it is called a phospho-diester bond.

Question 7. Find and write down structures of 10 interesting small molecular weight biomolecules. Find if there is any industry that manufactures the compounds by isolation. Find out who are the buyers.
Answer:

1. Sugar (Carbohydrates):

Amino Acids:

Fats:

Oils:

Question 8. Find out qualitative test proteins, fats, oils, and amino acids test any fruit juice, saliva, sweets, and urine for them.
Answer:

Biuret test for protein:

The biuret test Is a chemical test used for determining the presence of peptide bonds, In a positive test, a copper II ion (Cu;‘ Ion) Is reduced to copper (Cu’) which forms a complex with the nitrogen and carbon of peptide bonds in an alkaline solution. A violet color indicates the presence of protein.

Ninhydrin test for amino acid: 

• Ninhydrin is a chemical used to detect ammonia or primary and secondary amines.
• When reacting with these free amines, a deep blue or purple color known as Ruhemann’s purple is evolved.
• Most of the amino acids are hydrolyzed and reacted with ninhydrin except proline (a secondary amine).

Solubility test for fats and oils:

A positive solubility test for fats is that the fat dissolves in lighter fluid and not in water. In this test, 5 drops of fat or oil are added in two test tubes containing 10 drops of lighter fluid and 10 drops of cold water respectively.

• Fruit juice: Fruit juice contains sugar. So it cannot be tested by the above-mentioned test.
• Saliva: Saliva contains proteins, mineral salts, amylase, etc. So it can be tested for proteins and amino acids.
• Sweat: Sweat contains NaCl salts.
• Urine: Urine contains proteins. So it can be tested for proteins.

Karnataka Board Class 11 Biology Histology And Anatomy Of Flowering Plants Synopsis

Internal Morphology deals with the study of the internal structure of different plant
organs. It has two branches they are Histology and Anatomy.

• Histology is the study of different tissues present in the plant body.
• Anatomy deals with the study of gross internal details of plant organs like roots, j stems, leaves, flowers, etc.
• Tissues are functional units of an organ. Tissues are groups of cells having similar, functions and origins.
• Meristems are localised growth regions of the plant producing new tissues and organs throughout its life period. Based on origin- 2 types- primary meristem, and secondary meristem. Based on position – 3 types – apical, intercalary and lateral meristems.
• Permanent tissues have mature cells adapted to specific functions. Simple tissues have similar kinds of cells.
• Parenchyma is a fundamental living tissue with intercellular spaces.
• Collenchyma is a simple living mechanical tissue. Sclerenchyma is a simple dead mechanical tissue with lignified walls.
• Tissue systems are three types. They are- epidermal, ground and vascular. The epidermal tissue systems are made up of epidermal cells, stomata arid the epidermal appendages.
• The ground tissue system forms the main bulk of the plant. It is divided into three zones- cortex, pericycle and pith.
• The vascular tissue system is formed by the xylem and phloem. The general plant internal structure is similar in both dicot and monocot roots.
• Root TS shows 3 regions – epidermis, cortex and stele. The epidermis is an outermost layer with unicellular root hairs. Cuticle & stomata are absent. Exodermis contains suberised cells to prevent leakage of water.
• The general cortex is made up of parenchyma. Exodermis shows Casparian bands.

Stele consists of porlcyclo, vascular bundles, conjunctive tissues and pith. Pericycle is a singlo Inyorod pnronchymatoua cells. Poricyclo gives lateral roots. Vascular bundles are separate, radial, alternate and closed. Xylem i3 exarch. Stele is a monarch to autarch, generally tetrarch in dicot root and polyarch in monocot root.

• Pith is either scanty or absent in dicot root. It is large and well-developed in monocot root. Conjunctive tissue is present between the xylem and phloem strands.
• A typical dicot stem consists of epidermis, cortex and stele. A typical monocot stem shows epidermis, hypodermis, ground tissue and vascular bundles. The epidermis is a unique protective layer covered with a cuticle. Stomata help in the exchange of gases.
• Hypodermis is coilenchymatous in the dicot stem and sclerenchymatous in the monocot I stem. The general cortex in the dicot stem and ground tissue in the monocot stem are parenchymatous.
• Endodermis is distinct only in the dicot stem with Casparian strips. Stele is eustele in dicot stem and atactostele in monocot stem.
• Vascular bundles are few and arranged in a ring inside a pericycle in a dicot stem. They are numerous and scattered in the ground tissue in the monocot stem.
• Vascular bundles are conjoint, collateral and endarch. They are open in the dicot stem and closed in the monocot stem.
• Distinct pith and medullary rays are present in the dicot stem. The dicot leaf is dorsiventral and the monocot leaf is isobilateral.
• The epidermis covers the adaxial and abaxial surfaces of the leaf. Cuticle and stomata are present.
• Mesophyll is differentiated into upper palisade and lower spongy tissues in the dorsiventral leaf. It is undifferentiated arid homogeneous in an isobilateral leaf.
• Vascular bundles are collateral and closed. The xylem is on the upper side and the phloem is on the lower side. The vascular bundle is covered with a bundle sheath.

In Monocot leaf upper epidermis shows bulliform or motor cells. Secondary growth results in an increase in girth by the addition of secondary tissues. Interfascicular and intrafascicular cambia together form vascular cambium.

• The vascular cambium forms a secondary xylem inside and a secondary phloem on the exterior.
• Cork cambium develops from the cortical region. It produces cork towards the outside and secondary cortex on the inner side.
• Secondary xylem or wood forms the bulk of the tree. Production of secondary xylem is affected by seasonal change.
• Autumn wood and spring wood formed in one year together, constitute an annual ring. .
• Wood in the centre of the tree ceases to perform the function of conduction and is blocked by gums, resins, tyloses etc. It is called heartwood. Outer lighter sapwood is functional wood.
• Cork is a dead tissue containing suberised cells.
• Phellogen (cork cambium), phellem (cork) and phelloderm (secondary cortex) constitute periderm.
• Lenticels are lens-shaped openings found in the cork for gaseous exchange.
• All tissues outside the vascular cambium constitute bark.

Anatomy of Flowering Plants Very Short Answer Questions For Class 11

Question 1. The transverse section of a plant material shows the following anatomical features The vascular bundles are conjoint, scattered and surrounded by a sclerenchymatous bundle sheaths phloem parenchyma is absent. What will you identify it as?
Answer:

Monocotyledonous stem with closed vascular bundles.

Question 2. Why are the xylem and phloem called complex tissues?
Answer:

1. Complex tissues are made of more than one type of cells that work together as a unit.
2. Xylem and phloem are made of more than one type of cells i.e., parenchyma, fibres etc.

Question 3. How is the study of plant anatomy useful to us?
Answer:

Anatomy is useful to know the internal structure of the plant. It is useful in the classification of plants based on natural relations.  It is useful to understand the plant functions, habitat of the plant and evolution of plants.

Important Questions On Anatomy Of Flowering Plants Class 11 Karnataka Board

Question 4. The protoxylem is the first formed xylem. If the protoxylem lies radially next to the phloem, what kind of arrangement of xylem would you call it? Where do you find it?
Answer:

1. Radial arrangement
2. They are found in roots.

Question 5. What is the function of phloem parenchyma?
Answer: Phloem parenchyma stores food materials and other substances like resins, latex and mucilage.

Question 6. What is present on the surface of the leaves which helps the plant to prevent loss of water but is absent in roots? What is the epidermal cell modification in plants which prevents water loss
Answer:

1. Cuticle
2. Bulliforni cells are an Isobilateral (monocotyledonous) leaf.

Question 7. Which part of the plant would show the following?

1. Radial vascular bundle
2. Polyarch xylem
3. Well developed pith
4. Exarch xylem

Answer:

1. Radio vascular bundle – Root
2. Polyarch xylem- Monocot root
3. Well-developed pith – Monocot root
4. Exarch xylem  – Root

Question 8. What are the cells that make the leaves curl in plants during water stress? Give an example.
Answer:

1. Large, colourless Bulliform cells
2. Example: Monocot (Grass) leaves

Question 9. What constitutes the vascular cambial ring?
Answer:

1. Intrafascicular cambium and interfasicular cambium.
2. A cambial ring is formed in the dicot stem during secondary growth.

Question 10. Give one basic functional difference between phellogen and phelloderm.
Answer:

1. Phellogen (cork cambium) is a meristematic tissue, formed from the primary cortex.
2. Phelloderm (secondary cortex) is a permanent tissue formed by inner cells that are cut off from phellogen.

Question 11. If one debarks a tree, what parts of the plant are removed?
Answer:

1. Periderm and secondary phloem are removed.
2. All those tissues are exterior to the vascular cambium.

Question 12. Name the various kinds of dell layers which constitute the bark.
Answer: Periderm and secondary phloem.

Question 13. A student estimated the age of a tree to be about 300 years. How did he anatomically estimate the age of this tree ?
Answer:  The age of a plant can be estimated by counting the number of annual rings.

Question 14. Assume that you have removed the duramen part of a tree. Will the tree survive of die?
Answer: Plant survives because of the presence of sapwood which is meant for the conduction of water and minerals. Duramen is not useful for conduction.

Karnataka Board Class 11 Biology Chapter On Flowering Plants Short Question And Answers

Question 1 . State the location and function of different types of Meristems.
Answer:

Based on location. Meristems are three types:

1. Apical meristems :

They are present at ” the growing tips of roots, stem, branches etc., They help in the linear growth of the plant body. These are primary meristems because they appear early in life and contribute to the formation of the primary plant body.

2. Intercalary meristem:

They are found in between permanent tissues. This meristem is separated from the. apical meristems during plant growth. They help in the linear growth of the stem and leaves. Growth of flowers and fruits after their initiation at the apex also occurs due to these meristems. They are active only for a short period. These [_ are also primary meristems.

Example: Meristems seen at the base of internodes and leaf bases of monocotyledons (particularly grasses).

3. Lateral meristems :

They are found on the lateral sides of the plant body. The cells divide periclinally and increase the thickness of the organs like the stem and root. These are secondary meristems.

Example: Vascular cambium that helps in secondary growth by producing secondary xylem and secondary phloem; phellogen (cork cambium) that helps in the formation of periderm.

Question 2. Cut a transverse section of the young stem of a plant from your garden and observe it under the microscope. How would you ascertain whether it is a monocot stem or a dicot stem? Give reasons
Answer:

Class 11 Biology Anatomy Of Flowering Plants Questions

Question 3. A transverse section of the trunk of a tree shows concentric rings which are known as annual rings. How are these rings formed? What is the significance of these rings?
Answer:

1. In temperate and cold regions, the activity of cambium is influenced by seasonal variations.
2. In favourable conditions, growth will be active. So plants require large amounts of water and minerals. During unfavourable conditions, plants are less active.
3. In spring, the wood formed shows a greater number of xylem vessels having wide lumens. This is called spring wood or early wood.
4. During autumn, wood formed shows less number of xylem vessels with narrow lumens. This is called autumn wood or latewood.
5. Springwood and autumn wood appear alternately in the form of circles in the T.S. of a tree trunk. These are called Growth rings or annual rings.
6. By counting the number of annual rings the age of a tree can be estimated approximately.

Secondary xylem in an annual ring:

Question 4. What is the difference between lenticels and stomata?
Answer:

Lenticels :

Lens-shaped openings in the cork of woody trees are called lenticels. They show closely arranged parenchymatous cells. The lenticels permit the exchange of gases between the outer atmosphere and the internal tissues of the woody organs. There is no opening and closing mechanism.

Stomata :

Stomata are present in the upper epidermis and lower epidermis of leaves. They help in the exchange of gases. In dicot leaves, on either side of stomata kidney-shaped guard cells are present. In monocot leaves, dumbbell-shaped guard cells are present. Guard cell contains chloroplast. They help in the opening and closing of the stomata. Stomata help in the gaseous exchange and also promote transpiration.

Question 5. Write the precise function of

1. Sieve tube
2. Interfasicular cambium
3. Collenchyma
4. Sclerenchyma

Answer:

1. Sieve tube: The functions of the sieve tube are controlled by the nucleus of companion cells. The companion cells help in maintaining the pressure gradient in the sieve tubes. It transports food materials from leaves to other parts.
2. Interfascicular cambium: The cells of medullary cells adjoining the intrafascicular cambium become meristematic and form interfascicular cambium. Thus a continuous ring of vascular cambium is formed.
3. Collenchyma: The collenchyma cells which contain chloroplast are green in colour. Photosynthetic in function. Intercellular spaces are absent as the corners are thickened with pectin. So they provide tensile mechanical strength. It helps in the movement of the young stem, the petiole of the leaf, pedicle of the flower.
4. Sclerenchyma:  Sclerenchyma they are dead cells. Cell walls are thickened with lignin. Intercellular spaces are absent. So they, give mechanical strength to organs.

Question 6. The stomatal pore is guarded by two kidney-shaped guard cells. Name the epidermal cells surrounding the guard cells. How does a guard cell differ from an epidermal cell? Use a diagram to illustrate your answer.
Answer:

• The epidermal cells surrounding the guard cells are called subsidiary cells or accessory cells.
• The stoma is bounded by two kidney-shaped guard cells in dicots and dumbbell-shaped guard cells in monocots.
• Unlike that of other epidermal cells, guard cells possess chloroplast. The wall of the guard cells towards the stomatal pore is thick, while the outer wall is thin.
• The stoma, guard cell and subsidiary cells together constitute the stomatal complex.

Stomata of Dicot leaf & Monocot leaf:

Question 7. Point out the differences in the anatomy of the leaf of peepal (Ficus religiosaj and maize (Zea mays].
Answer:

Dicot Leaf And Monocot Leaf:

Karnataka Board solutions for Anatomy of Flowering Plants

Question 8. Draw the diagrams and label the differences.
Answer:

1. The internal structure of the Dicot leaf:

Example: Peepal:

2. The internal structure of Monocot leaf:

Example: Maize

Question 9. The Cork cambium forms tissues that form the cork. Do you agree with this statement? Explain.
Answer:

Yes, Cork cambium or phellogen is a secondary meristematic tissue. It can divide. It divides and forms new cells on both sides. The tissue produced outside is called cork tissue or phellem. The tissue is produced towards an inner side in the secondary cortex or phelloderm.

Question 10. Name the three basic tissue systems in flowering plants. Give the tissue names under each system.
Answer:

The three basic tissue systems in flowering plants are

1. Epidermal tissue system
2. The ground or fundamental tissue system
3. The vascular or conducting tissue system.
4. The epidermal tissue system consists of parenchymatous tissue. They are epidermis, stomata and outgrowths.
5. The ground or fundamental tissue system consists of simple tissues such as parenchyma, collenchyma and sclerenchyma.
6. The vascular or conducting tissue system consists of complex tissues, the phloem and the xylem.

Question 11.  Every 50 years, for 200 years, a nail was drilled into a tree to the same depth and at exactly 1m above the soil surface [assuming the ground level has not changed). What will be the pattern of the four nails on the tree? Do you know the reason for your answer? If yes give the reason.
Answer:

• The heads of all four nails are at the same level.
• The Stem of the plant undergoes later growth due to cambial activity. Hence, the growth (circumference) of the stem increases.
• All the four nails will be seen in the xylem portion of the stem.
• There will not be a change in nail position concerning vertical position from ground level. Because the vertical growth is reduced after some period and lateral growth is promoted in plants.

Question 12. Why is wood made of an xylem and not a phloem?
Answer:

• The cambial ring produces more xylem than phloem during secondary growth.
• Xylem except parenchyma, consists of dead tissues i.e., tracheids, vessels and fibres.
• Phloem is living complex tissue, except fibres (bast).
• Hence wood is made of xylem.

Long Answer Questions On Anatomy Of Flowering Plants for Class 11

Question 1. Explain the process of secondary growth in the stems of woody angiosperms with the help of schematic diagrams. What is its significance?
Or
What is periderm? How does periderm formation take place in the dicot stems?
Answer:

The growth of a stem or root in thickness due to the formation of secondary tissues due to the activity of primary and secondary meristems is called secondary growth.

Changes during the secondary growth of a dicot stem are divided into two groups.

They are

1. Intrastelar secondary growth.
2. Extrastelar secondary growth.

1. Intrastelar secondary growth :

The changes that occur inside the stele are called Intrastelar secondary growth. They are

Formation of vascular.cambial ring :

• Indicot stem, vascular bundles are in a circular ring. They are the open type with fascicular cambium.
• Parenchyma in medullary rays dedifferentiates into secondary meristem connecting fascicular cambium. These are called interfascicular cambiam.
• Fascicular and interfascicular cambia fuse to form vascular cambial ring.

The activity of vascular cambium :

• The vascular cambium has 2 types of initials.
  1. Fusiform initials: They give rise to the secondary xylem towards the centre and secondary phloem to the outside.
  2. Ray initials: They produce phloem rays towards the outside and xylem rays towards the inside.
• More secondary xylem is formed than secondary phloem.
• The secondary xylem is called wood and the secondary phloem bast.
• Stages of secondary growth in Dicot stem
• As the stem increases in thickness primary phloem and primary xylem are crushed and removed.
• The secondary xylem has vessels, fibres and xylem perenchyma. Vessels are pitted.
• The secondary phloem has sieve tubes, companion cells, fibres and phloem parenchyma.
• Xylem rays and phloem rays are also called vascular rays. They are helpful in lateral conduction and storage.

Stages of secondary growth in Dicot stem:

2. Extrastelar secondary growth: The changes which occur outside the stele are called Extrastelar secondary growth.

1. Due to the formation of more secondary vascular tissues pressure is exerted on the epidermis causing its rupture. So a secondary protective layer (periderm) is formed.
2. Parenchyma cells in the middle or inner cortex differentiate into a ring of secondary meristem. This is called cork cambium or phellogen. It cuts off new cells on both sides
3. Tissue produced on the outside is called cork tissue or phellem. The tissue produced inside is called the secondary cortex or phelloderm.
4. The phellogen, phellem, and phelloderm together constitute periderm.
5. To facilitate gaseous exchange in the cork tissue certain bulged lens-shaped structures are formed. They are called lenticels.

Question 2. Draw illustrations to bring out the anatomical differences between

1. Monocot root and Dicot root
2. Monocot stem and Dicot stem

Answer: 

1. Monocot root and Dicot root:

2. Monocot stem and Dicot stem:

Class 11 Biology Chapter On Flowering Plants Notes And answers

Question  3. What are simple tissues? Describe various types of simple tissues.
Answer:

The tissues which are made of only one type of cells are called simple tissues. The various types of simple tissues are parenchyma, collenchyma and sclerenchyma.

Parenchyma :

1. The Parenchyma is a living tissue. It occupies a major part of the plant body. So it is known as fundamental tissue or ground tissue.
2. The cells are isodiametric. They may be spherical, oval-round, polygonal or elongated in shape.
3. Cell walls are thin, and made up of cellulose.
4. Intercellular spaces may be present or absent.
5. Parenchyma performs functions like photosynthesis, storage, and secretion.

Collonchyma :

• Collenchyma Is a living mechanical tissue.
• It Is present below the epidermis in dicot plants.
• It is present as a continuous hypodermal ring
• Example: Helianthus annus or as a discontinuous ring (Cucurbita)
  • Corners are thickened due to cellulose, hemicellulose and pectin.
  • Intercellular spaces are absent.
  • It provides mechanical support to the growing parts of the plant parts such as the young stem, petiole, pedicle etc.
  • In the cytoplasm, if chloroplast is present, photosynthetic in function.

Scelerenchyma :

• Sclerenchyma is a dead mechanical tissue.
• Cells are long and narrow.
• Cell walls are thickened with lignin with pits.
• They are dead cells. Protoplast is absent.
• Based upon the structure, origin and development sclerenchyma are two types -fibres, and sclereids.
• Fibres are thick-walled, elongated and pointed cells.
• Sclereids (stone cells) are spherical, oval or cylindrical.
• Cell walls are highly thickened, lumen is very narrow.
• Sclereides are found in fleshy fruits like guava, pear and sapota.
• Seed coat of legumes, leaves of tea, fruit wall of nuts etc.
• Their main function is to give mechanical support.

Question 4. What are complex tissues? Describe various types of complex tissues.
Answer:

• Tissues which are made up of more than one type of cells and work together as a unit are called complex tissues.
• The xylem and phloem are complex tissues.

Xylem:

The main function of the xylem is to conduct water and minerals from the roots to the stem and leaves. Xylem also provides mechanical strength to plant parts

Xylem consists of:

1. Tracheids
2. Vessels
3. Xylem fibres
4. Xylem Parenchyma.

These are 

1. Tracheids: Tracheids are elongated or tube-like cells with thick and lignified walls and tapering ends. These are dead cells without protoplasm. Its main function is water transport
2. Vessels: The presence of vessels is an important character found in angiosperms. Vessels
   are absent in Gymnosperms. Vessels are dead cells without protoplasm. The cells are elongated or tube-like cells thickened with lignin. Its main function Is water transport.
3.  Xylem fibres: These are highly thickened with lignin with a narrow central lumen. They may be septate or aseptate.
4. Xylem Parenchyma: These are living cells. Cell walls are thickened with cellulose. They store food materials like starch, fats, and tannins. The ray parenchyma cell helps in the radial conduction of water.

Primary xylem is of two types – protoxylem and metaxylem.

The first formed primary xylem elements are called protoxylem. The later-formed primary xylem is called the metaxylem.

1. In stems, the protoxylem is towards the centre and the metaxylem is towards the periphery. It is called endarch.
2. In roots, the protoxylem is towards the periphery and the metaxylem is towards the centre. It is called an exarch.

Phloem:

The main function of phloem transport food materials usually from leaves to the other parts of the plant body.

Phloem contains:

1. Sieve tube elements
2. Companion cells
3. Phloem parenchyma
4. Phloem fibres.

These are

1. Sieve tube elements:  These are long, tube-like structures arranged longitudinally and are associated with companion cells. Their end walls are perforated in a sieve¬ manner to form sieve plates. A mature sieve tube element possesses a peripheral cytoplasm and a large vacuole but lacks a nucleus. The function of sieve tubes are controlled by the nucleus of companion cells.
2. Companion cells: These are specialized parenchymatous cells which are closely associated with sieve tube elements. Both are connected by pit fields present between their common longitudinal walls.
3.  Phloem parenchyma: These are parenchyma cells in the phloem with tapering cylindrical cells which have dense cytoplasm and nucleus. They store food materials and other substances like resin, latex etc.
4.  Phloem fibres (bast fibres): These are sclerenchymatous cells. The cell wall is thick. At maturity, they lose their protoplasm and become dead.

Question 5. Describe the internal structure of the dorsiventral leaf with the help of a labelled diagram.
Answer:

The transverse section of a dicot leaf or dorsiventral leaf shows three parts- epidermis, mesophyll and vascular bundles.

1. Epidermis :

• It is the outermost layer of leaf with one cell thickness.
• Cells are barrel-shaped. They are arranged compactly without intercellular spaces.
• The epidermis present on the upper (adaxial) side is called the upper epidermis.
• The epidermis on the lower (abaxial) side Is called lower epidermis
• The outer surface of the epidermis is covered by a waxy layer called a Cuticle.
• The epidermis shows multicellular hairs.
• Stomata are present. They are more on lower surface than the upper surface.
• The epidermis gives protection to the inner tissues. The cuticle regulates transpiration. Stomata help in exchange of gases.

2. Mesophyll :

Ground tissue present in between the two epidermal layers is called Mesophyll. It is Chlorenchymatous.

• In the dorsiventral leaf, mesophyll is differentiated into two parts- palisade parenchyma and spongy parenchyma.

Palisade parenchyma: 

• Palisade parenchyma is found beneath the upper epidermis. Elongated and columnar cells are arranged in i – 3 rows.
• Intercellular spaces are narrow. Cells have a large number of chloroplasts nearer to the cell wall. (So the upper side of the leaf is dark green in colour). Palisade tissue is mainly concerned with the assimilation of carbohydrates.

Spongy parenchyma:  Spongy parenchyma Is found towards the lower epidermis.

• It has 3 rows of irregularly shaped and loosely arranged cells. Intercellular spaces are large. Air cavities are found below the stomata.
• Cells have less number of chloroplasts. (So the lower side, of the leaf is pale green) Spongy Parenchyma facilitates gaseous exchange. They also help in the synthesis of food materials;

3. Vascular Bundle :

• Vascular bundles are extended in the mesophyll in the form of veins.
• Vascular bundles are bigger at the base of the leaf blade and gradually become smaller towards the margins and apex.
• Vascular bundles are conjoint, collateral and closed. Xylem is present towards the upper side and phloem towards the lower side.
• Vascular bundles help in the conduction of water, mineral salts and food materials.
• They also provide mechanical strength to the leaf.
• Each vascular bundle is enclosed by a layer of special mesophyll cells arranged compactly. This layer is called the Bundle sheath or Border parenchyma.
• Cells of the bundle sheath divide and extend towards both epidermal layers.
• These are called bundle sheath extensions. They help in the conduction of food materials from mesophyll cells to vascular bundles.

Question 6. Describe the internal structure of an isobilateral leaf with the help of a labelled diagram.
Answer:

• The transverse section of the monocot or isobilateral leaf shows three parts- epidermis, mesophyll and vascular bundles.
• This Is the outermost layer on both sides of the leaf. Cells are one cell in thickness. They are barrel-shaped and closely packed without Intercellular spaces.
• It is covered by a waxy layer called the cuticle.
• The epidermis on the adaxial (upper) surface is called the upper epidermis. The epidermis on the abaxial (lower) surface is called the lower epidermis.
• Hairs are absent. Stomata are present on both sides in equal numbers.
• In grasses, specialised cells are present in the upper epidermis. They are called bulliform cells or motor cells. They are thin-walled and filled with water.
• They help in rolling and unrolling of the leaf.
• The epidermis gives protection to inner tissues. The cuticle regulates transpiration.
• Stomata help in the exchange of gases.

2. Mesophyll :

1. Ground tissue present between two epidermal layers is called mesophyll.
2. It is chlorenchymatous.
3. Mesophyll is undifferentiated.
4. Cells have chloroplasts and perform the assimilation of carbohydrates.
5. Sometimes patches of sclerenchyma are found beneath the epidermis.
6. They provide mechanical strength.

3. Vascular Bundles :

1. Vascular bundles are present in the mesophyll in the form of veins.
2. Vascular bundles are conjoint, collateral and endarch.
3. Xylem is present on the upper side and phloem is present on the lower
   side.
4. Veins help in the conduction of water, mineral salts and food materials. They
   also provide mechanical strength.
5. Each vascular bundle is enclosed by a layer of special mesophyll cells called
   bundle sheath or border parenchyma.
6. Cells present on either side of vascular bundles towards the upper and lower epidermis are Called bundle sheath extensions.
7. In many monocots, they are sclerenchymatous and provide mechanical support.

Question 7. Distinguish between the following :
Answer:

1. Exarch and endarch condition of protoxylem
2. Stole and vascular bundle.
3. Protoxylem and metaxylem
4. Interfasicular cambium and intrafasicular cambium
5. Open and closed vascular bundles
6. Stem hair and root hair
7. Heartwood and sap wood.
8. Springwood and autumn wood.

Answer:

1. In roots, the protoxylem lies towards the periphery and the metaxylem lies towards the centre. Such type of protoxylem is called Exarch. In stems, the protoxylem lies towards the centre (pitch) and the metaxylem lies towards the periphery of the organ. Such a type of protoxylem is called Endarch.

2. Stele :

The stele is the central conducting cylinder. Generally it may have pericycle, vascular bundle, medulla and conjunctive tissue or medullary rays.

• Vascular bundles: Xylem and phloem are present in vascular bundles. Xylem conducts water and phloem conducts food materials.

3. Protoxylem: The first formed primary xylem elements are called protoxylem.

• Metaxylem: Later-formed primary xylem elements are called metaxylem.

4. Intrafasicular cambium:

Cambium present between the primary xylem and primary phloem is called Intrafasicular cambium. It is present inside vascular bundle (Intra = Inside; fascicular = vascular bundle)

• Interfascicular cambium : The cells in medullary rays become meristematic and form interfascicular cambium (Inter = in between; fascicular = vascular bundle)

5. Open vascular bundle: The vascular bundle which have a cambium between the xylem and phloem are called the open vascular bundle.

• Closed vascular bundle: In these vascular bundles cambium is absent between the xylem and phloem.

6. Stem hair and root hair:

• Stem hair : Multicellular hairs present on the stem an stem hair or trichomes. Their main function is to prevent the entry of pathogens.
• Root hair: Unicellular hairs present on the root are root hair. Their main function is absorption of water.

7. Heartwood and sapwood :

• Heartwood: The dark brown-coloured central part of the secondary xylem comprising of dead elements with highly lignified walls is called heart wood. It is infiltrated with various organic compounds like tannins, resins, oils, gums, aromatic substances and essential oils. The heartwood does not conduct water but it gives mechanical support to the stem.
• Sapwood: The peripheral region of the secondary xylem is lighter in colour and is known as sap wood. It conducts water and minerals from root to leaf.

8. Springwood and Autumn wood:

Anatomy of Flowering Plants key questions Class 11

Question 8. What is stomatal apparatus? Describe the structure of stomata with a labelled diagram.
Answer:

Structure of stomata :

• Tiny pores in the epidermis of young aerial parts of the plant are called stomata.
• Stomata are more abundant in the leaf epidermis.
• The stoma is bounded by two kidney-shaped guard cells in dicots and dumbbell¬ shaped guard cells in monocots.
  • Example: Grasses).
• Unlike that of other epidermal cells, guard cells possess chloroplasts.
• The wall of the guard cell towards the stomatal pore is thick, while the outer wall is thin.
• Epidermal cells surrounding guard cells are called subsidiary or accessory cells.
• They differ from other epidermal cells in their shape and position.
• The stoma is followed by an air cavity called a substomatal cavity in the mesophyll.
• The stoma, guard cells and subsidiary cells together constitute the stomatal apparatus.

Question 9. Describe the T.S of a dicot stem
Answer:

Internal structure of young dlcot stem – Example: Hellanthus annuus

The transverse section of a dicot stem shows three distinct zones – epidermis; cortex and stele.

1. Epidermis :

• The outermost layer in the young dicot stem is called the epidermis. It is one cell in thickness.
• Cells are tubular or rectangular. They are arranged compactly without intercellular spaces.
• The outer surface of the epidermis is covered by a waxy substance called cutin. This layer is called the cuticle.
• Minute pores found in the epidermis are called stomata.
• Multicellular. hairs developing on the epidermis are called trichomes.
• The epidermis gives protection to the inner tissues.
• Stomata facilitate the exchange of gases and promote transpiration.
• Cuticle and trichomes check transpiration. They also protect the stem from high temperatures.
• Trichomes also help in preventing the entry of pathogenic micro-organisms.

2. Cortex :

It is extrastelar ground tissue. It shows three subzones -hypodermis, general cortex and endodermis.

 Hypodermis :

• The layer present below the epidermis is called hypodermis.
• It consists of 3- 6 layers of Collenchyma.
• Cells are arranged compactly without intercellular spaces. They show excessively thickened corners.
• Hypodermis helps in providing tensile strength to the stem.
• Hypodermis also helps in the production offood materials by having chloroplasts.

General Cortex :

• It is found below the hypodermis.
• It consists of 5-10 rows of parenchyma.
• Cells are isodiametric or oval or spherical.
• Resin or latex ducts may be present in it.
• Outer layers of cells have chloroplasts and perform assimilation of food materials.
• The inner layers are concerned with the storage of food.

 Endodermis:

• It Is the Innermost layer of the cortex.
• It Is in one layer with barrel-shaped, compactly arranged cells.
• Radial and transverse walls show Casparian bands.
• Endodermal cells store starch grains. So it is known as a starch sheath.

3. Stele: A central conducting cylinder is called a stele. It occupies a major portion of the stem. It shows four parts.

 Pericycle :

• It is the outermost layer of the stele.
• It lies, between endodermis and vascular bundles.
• It has alternate patches of sclerenchyma and parenchyma.

Vascular Bundles :

• Each vascular bundle is wedge or top-shaped.
• A limited number of vascular bundles are arranged in the shape of a circular ring. Such an arrangement is called Eustele.
• In each vascular bundle, the phloem is present outside and the xylem towards the inside on the same radius. So vascular bundle is conjoint and collateral.
• Meristematic tissue is present in between the xylem and phloem. It is called fascicular cambium. A vascular bundle with cambium is called an open type.
• The xylem is endarch (protoxylem towards the centre).
• Xylem has vessels and xylem parenchyma. Tracheids and fibres are also present. Xylem conducts water and salts.
• Phloem has sieve tubes, companion cells, phloem parenchyma and fibres. It conducts food materials.

Medulla :

The central part of the stele is called the medulla.  It is filled with parenchyma. It is well-developed and extensive. It stores food materials.

Medullary rays :

• The medulla extends, to the periphery in between the vascular bundles forming medullary rays. Parenchymatous cells are living, thin-walled and elongate radially.
• Medullary rays connect the stele and cortex. They help in lateral conduction.

Question 10. Describe the T.S. of monocot stem.
Answer:

The internal structure of Monocot Stem :

The anatomy of the Monocot stem shows four distinct parts- Epidermis, hypodermis, ground tissue, and vascular bundles. A distinct cortex is absent. Endodermis, pericycle, medulla, and medullary rays are absent.

1. Epidermis

• The outermost layer is called the epidermis. It Is made up of living, rectangular or tabular cells. They are arranged compactly without Intercellular spaces.
• A waxy layer is deposited on the outer surface of the epidermis. This is called the cuticle.
• Trichomes are absent. Numerous stomata are found in the epidermis.
• The epidermis gives protection to inner tissues. Stomata help in the exchange of gases. Cuticle prevents evaporation of water.

Hypodermis :

It is present beneath the epidermis. It is made up of 1- 4 rows of thick-walled sclerenchymatous fibres. Intercellular spaces are absent. It gives mechanical strength to the stem.

3.  Ground Tissue :

• The tissue next to the hypodermis filling the remaining part of the stem (except vascular bundles) is called ground tissue.
• It is parenchymatous.
• Cells are thin-walled with or without chloroplasts. They are loosely packed with intercellular spaces.
• It is mainly concerned with the synthesis and storage of food materials.

4. Vascular Bundles :

• Numerous bundles are irregularly scattered in the ground tissue. Such an arrangement is called Atactostele.
• Inner bundles are bigger. Peripheral bundles are small in size. They are oval in shape.
• Each vascular bundle is enclosed by a sclerenchymatous sheath. So it is called a fibrovascular bundle.
• Each bundle has a phloem towards the outside and a xylem towards the inside of the radius. So it Is described as conjoint and collateral. bundle on the same concerned with the conduction of water, salts and food
• Vascular bundles are materials.
• Cambium Is absent between the xylem and phloem. So the vascular bundle is a closed type.
• The xylem is endarch (protoxylem towards the centre). Xylem consists of tracheids, vessels, fibres and xylem parenchyma.
• The xylem is arranged in the shape of Y. Out of four xylem vessels, two are metaxylem and two are protoxylem vessels. It stores water.
• Phloem has sieve tubes and companion cells. Phloem parenchyma is an absent sheath

Question 11. Describe the internal structure of a dicot root.
Answer:

The internal structure of the primary dicot root has three zones- epidermis, cortex, and stele. The cortex is bigger than the stele.

1. Epidermis :

• It is the outermost layer of thin-walled rectangular living cells arranged compactly without intercellular spaces.
• Cuticle and stomata are absent.
• Some epidermal cells (trichoblasts) produce tubular extensions called root hairs. Cells giving rise to root hairs are smaller than other epidermal cells. The Epidermis of the root is called rhizodermis or piliferous layer or epiblema due to the presence of root hairs.
• Root hairs absorb capillary water. The epidermis gives protection to the inner tissues.

2. Cortex :

The ground tissue system extending from the epidermis to the stele is called the cortex. It is differentiated into three parts.

Exodermis :

• The outermost layer of the cortex with 2 or 3 rows of suberised thick-walled cells is called exodermis.
• It acts as a protective layer when the epidermis is removed.
• It prevents the exit of water from the cortex.

General cortex :

• It is present beneath the exodermis.
• It has several layers of loosely arranged thin-walled parenchyma intercellular.
• spaces are present.
• Cells store food materials.
• The general cortex helps in the lateral conduction of water from the epidermis to the xylem vessels.

Endodermis :

• It is the innermost layer of the cortex.
• It is made up of a single layer of barrel-shaped cells.
• Radial and transverse walls of endodermal cells show thickening due to the deposition of lignin and suberin. These are called Casparian thickenings. It is a characteristic feature of the endodermis.
• Endodermal cells present opposite to protoxylem are thin-walled without Casparian strips. These cells are called passage cells.
• Passage cells help in the entry of water and salts from the cortex into the stele.

3. Stele: The central conducting cylinder Is called the stele. It shows three parts.

• Pericyte :
  • It Is the outer layer of the stele. It Is uniseriate with thin-walled rectangular parenchymatous cells.
  • Pericycle gives rise to lateral roots.
  • It also helps in secondary growth.
• Vascular bundles: Xylem and phloem are arranged alternately on separate radii.
  • So vascular bundles are separate or radial.
  • Xylem and phloem conduct water and food materials respectively.
  • The protoxylem is towards the pericycle and the metaxylem is towards the centre. So the xylem is exarch.
  • Xylem is variable from monarch to octarch (xylem groups 1-8) usually tetrarch (4 xylem groups alternating with 4 phloem bundles). Monarch Trapa, Tetrarch – Gossypium, Octarch – Costanea,
  • Cambium is absent.
  • Parenchyma tissue extending between the xylem and phloem strands is called conjunctive tissue. It helps in the storage of food materials.
• Pith or Medulla:
  • The central portion of the stele is called the medulla or pith. It may be completely absent in the dicot root.
  • When it is present, it is parenchymatous. It helps in the storage of food and water.

Karnataka Board Class 11 Biology Chapter Question And Answers

Question 12. Describe the internal structure of a monocot root.
Answer:

The internal structure of the monocot root is differentiated into three zones- epidermis, cortex and stele.

1. Epidermis :

• The outermost layer is called the epidermis. Cells are living, rectangular, thin-walled. They are compactly arranged without intercellular spaces.
• Cuticle and stomata are absent.
• Some cells (trichoblasts) show tubular extensions- root hairs. The Epidermis of the root having root hairs is called epiblema or piliferous layer or rhizodermis.
• Root hairs help in the absorption of capillary water from the soil. The epidermis gives protection to the inner tissues.

2. Cortex :

This is the ground tissue system extending from the epidermis to the stele. It is differentiated into three parts.

Exodermis :

• It is the outermost layer of the cortex with 2 or 3 rows of cells. Cell walls are thick and suberised.
• It acts as a protective layer when the epidermis is removed.
• It prevents the exit of water from the cortex.

General cortex :

• It is present beneath the exodermis.
• It has several layers of loosely arranged thin-walled parenchyma.
• Intercellular spaces are present.
• Cells store food materials lateral conduction of water Irom epidermis to xylem vessels.

Endodermis :

• It is the innermost layer of the cortex.
• It is made up of a single layer of barrel-shaped cells.
• Radial and transverse walls of endodermal cells show thickening due to the deposition of lignin and suberin. These are called Casparian thickenings.
• Endodermal cells present opposite to protoxylem are thin-walled without Casparian strips. These cells are called passage cells.
• Passage cells help in the entry of water and salts from the cortex into the stele.

3. Stele:

The central conducting cylinder is called a stele. It is very prominent and bigger in size. It shows three parts.

Pericycle :

• It is the outermost layer of the stele. It is. uniseriate with thin-walled parenchymatous cells.
• Pericycle gives rise to lateral roots.
• In old roots it becomes sclerenchymatous and gives mechanical strength.

Vascular bundles :

• The xylem and phloem are arranged alternately on separate radii. So vascular bundles are radial or separate.
• The protoxylem is towards the pericycle and metaxylem towards the centre. So xyl is exarch.
• The xylem is polyarch (numerous xylem groups).
• Cambium is absent.
• The Xylem Is concerned with the conduction of water and salts. Phloem conducts organic solutes.
• Parenchyma tissue extending between the xylem and phloem strands is called conjunctive tissue.
• Cells are rarely thick-walled. It is helpful in the storage of food and provides mechanical strength. mechanical strength.

Karnataka Board Class 11 Biology Cell Cycle And Cell Division Synopsis

Cell division is a process by which a cell duplicates for the growth and reproduction of an organism.

• Virchow proposed that new cells arise from pre-existing cells by division. This is called cell lineage theory
• Somatic cells divide by a process of mitosis while the germ cells divide by a process called meiosis (reduction division).
• In mitosis, daughter cells have the same number of chromosomes as the parent cell.
• Duplication of DNA molecules and doubling of chromosomal constituents are observed during the S – phase of interphase.
• Mitosis includes karyokinesis and cytokinesis. Karyokinesis occurs in four stages.
• During prophase nucleolus and nuclear membrane, disappear. Chromatin condenses into chromosomes, each having two chromatids.
• During metaphase, spindle fibers are formed. Spindle fibers attach to the centromere of chromosomes. Chromosomes move to the center of the spindle.
• In Anaphase centromere divides. Daughter chromosomes move to opposite poles.
• In Telophase nucleolus and nuclear membrane reappear. Chromosomes decondense into chromatin. Two daughter nuclei are formed.
• Cytokinesis is by cell plate method. Two daughter cells are formed.
• In meiosis, karyokinesis and cytokinesis occur two times.
• Meiosis I is a reductional division.
• Prophase I is the longest stage and is divided into 5 stages.
• In leptotene, chromosomes become distinct being quite long and uncoiled.
• In zygotene, pairing of homologous chromosomes – synapsis occurs.
• In pachytene, an exchange of genetic material (crossing over) occurs between non-sister chromatids of the bivalent.
• In diplotene, repulsion starts between homologous. Chiasmata show terminalisation process.
• In diakinesis, the nucleolus and nuclear membrane disappear.
• In metaphase 1, the bivalents come to lie at the equator
• In anaphase 1, homologous chromosomes separate. Each chromosome of a pair moves to opposite poles of the spindle.
• Each chromosome of a pair moves to opposite poles of the spindle.
• Information Telophase 1 reappearance of nuclide and nuclear membrane results in the formation of two haploid nuclei.
• The events Four of meiosis 2 are similar to mitotic division. Thus it is an equational division. Four haploid cells are formed. The daughter cells produced are called gametes or spores
• Crossing and over evolution results in exchange species. of genetic information between individuals

Cell Cycle And Cell Division Very Short Question And Answers

Question 1. Between a prokaryote and a eukaryote, which cell has a shorter cell division time?
Answer:

• A prokaryotic cell has a shorter cell division time due to a shorter cell cycle.
• For instance, the bacterial cell cycle is 20 minutes as compared to 90 minutes of cell cycle in yeast.

Question 2. Among prokaryotes and eukaryotes, which one has a shorter duration of cell cycle?
Answer:

• Prokaryotes
• Bacteria (prokaryote) cell cycle is 20 minutes and in human cells (Eukaryote) it is 24 hours.

Question 3. Which of the phases of the cell cycle is of the longest duration?
Answer:

• Interphase
• In the human cell cycle of 24 hours, the interphase lasts for 23 hours (about 95% of the total duration).

Question 4. Which tissue of animals and plants exhibits meiosis?
Answer:

• Reproductive tissue – Gamete mother cells.
• Diploid cells undergo meiosis to produce haploid sex cells.

Cell Cycle and Cell Division For Class 11 Karnataka

Question 5. Given that the average duplication time of E.coli is 20 minutes. How much time will two E.coli cells take to become 32 cells?
Answer:

• 80 minutes.
• It takes 4 cell divisions to form 32 cells from the initial 2 cells.

Question 6. Which part of the human body should one use to demonstrate stages of mitosis?
Answer:

The cells of the upper layer of the epidermis, cells of the lining of the gut, and blood cells (bone marrow). The above cells of the human body are being constantly replaced.

Question 7. What attributes does a chromatid require to be classified chromosome?
Answer:

Two chromatids are attached to the centromere.

Question 8. Which of the four chromatids of a bivalent at prophase – 1 of meiosis can be involved in cross-over? 
Answer:

• Nonsister chromatids of the homologous chromosomes (a bivalent).
• Crossing over occurs in the pachytene stage of Prophase – 1 in Meiosis

Question 9. If the tissue has at a given time 1024 cells, how many cycles of mitosis, had the original parental single cell undergone? 
Answer:

• Cycles of mitosis,
• Mitosis Is equatorial cell division and the doubling of cell number occurs per cell division.

Question 10. An anther has 1200 pollen grains. How many pollen mother cells must have been there to produce them?
Answer:

• 300 pollen mother cells.
• Due to meiosis, each PMC produces 4 pollen grains.

Question 11. At what stage of the cell cycle does DNA synthesis occur?
Answer:

• S or Synthetic phase of Interphase.
• During S phase 2C DNA increases to 4C DNAnswer:

Question 12. One cycle of cell division in human cells (eukaryotic cells) takes 24 hours. Which phase of the cycle, do you think occupies the maximum part of the cell cycle?
Answer:

• Interphase occupies the maximum time i.e., 23 hours.
• It is about 95% of the total duration of the cell cycle in human cells.

Question 13. It is observed that heart cells do not exhibit cell division. Such cells do not divide further and exit phase to enter an inactive stage called
Answer:

• G phase
• Quiescent stage (Go)

Question 14. Identify the substages of prophase – 1 in Meiosis in which synapsis and desynapsis are formed.
Answer:

• Synopsis (pairing of homologous chromosomes) occurs in the zygotene substage of prophase – 1 in meiosis.
• Desynapsis (separation of homologous chromosomes) occurs in the Diplotene substage of prophase – 1 in meiosis. of cell cycle. Fill in the blanks.

Question 15. Name the stage of meiosis in which actual reduction in chromosome number occurs.
Answer:

• Anaphase – 1 in Meiosis I
• During this stage, homologous chromosomes migrate to opposite poles.

Question 16. Mitochondria and plastids have their DNA (genetic material). What is their fate during nuclear division like mitosis?
Answer:

• Mitochondria and plastids have no role during the nuclear division of mitosis.
• At the time of cytoplasmic division, mitochondria and plastids get distributed between the two daughter cells.

Question 17. A cell has 32 chromosomes. It undergoes mitotic division. What will be the chromosome number during metaphase? What would be the DNA content (C) during anaphase?
Answer:

• The chromosome number in the cell at the metaphase of mitosis is 32 only. But each chromosome consists of 2 sister chromatids.
• In anaphase, two sister (daughter) chromatids of a chromosome are separated and move to opposite poles. Each of the separated chromatids consists of 2C and DNA.

Question 18. While examining the mitotic tissue, one finds some cells with 16 chromosomes and some with 32 chromosomes. what possible reasons could you give for this difference in chromosomes that could have arisen from cells with 32 chromosomes or vice versa?
Answer:

• In mitosis cells at prophase and metaphase consist of basic sets of chromosomes, i.e., in this case, 2m = 16.
• But at anaphase splitting of two sister (daughter) chromatids of a chromosome leads to a doubling of number i.e., 32 that distribute equally (16 each) among two daughter cells formed from a mother cell.

Cell Cycle And Cell Division Key Questions Class 11

Question 19. The following events occur during the various phases of the cell cycle. Fill in the blanks with a suitable answer against each.

1. Disintegration of nuclear membrane _______________________
2. Appearance of nucleolus _______________________
3. Division of centromere _______________________
4. Replication of DNA _______________________

Answer:

1. Prophase
2. Telophase and Interphase.
3. Anaphase
4. S (Synthesis) phase in Interphase.

Question 20. Two key events take place during the s-phase in animal cells – DNA replication and duplication of centriole. In which parts of the cell do these events occur?
Answer:

• DNA replication occurs in chromosomes present in the nucleus during the s-phase of Interphase.
• Centriole duplication occurs in the cytoplasm.

Question 21. Name a cell that is found arrested in the diplotene stage for months and years. Comment in two or three sentences, how it completes cell cycle.
Answer:

• Oocytes of some vertebrates, diplotene can last for months or years.
• Terminalizationofchiasmataoccursin diakinesis and homologous chromosomes separated. Subsequently, cell enters into other stages of MeiosisI for the reduction of chromosome number
• Meiosis 2 results in the formation of 4 daughter cells each with a haploid chromosome set.

Question 22. Name a stain commonly used to color chromosomes.
Answer: Acetocarmine

Question 23. Name the pathological condition when uncontrolled cell division
Answer: Cancer

Question 24. Meiosis has events that lead to both gene recombinations as well as Mendelian recombinations! Discuss,
Answer:

Both chiasmata and crossing over occur between non-sister chromatids. Due to crossing over, genetic recombinations are caused. During Anaphase – 1 of meiosis – 1, Mendelian recombination takes place.

Question 25. Both unicellular and multicellular organisms undergo mitosis. What are the differences, if any, observed between the two processes?
Answer:

In unicellular organisms, a cell divides into two halves by binary fission. Stages like Prophase, Metaphase, Anaphase, and Telophase are present in multicellular organisms. It’s not present in unicellular organisms

Karnataka Board Solutions For Class 11 Biology Chapter 10 Cell Cycle And Cell Division Short Question And Answers

Question 1. In which phase of meiosis are the following forms? Choose the answers given below 

1. Synaptonemal complex ________________________
2. Recombination nodules _______________________
3. Appearance/activation of _______________________
4. Termination of chiasmata  _______________________
5. Interkinesis _______________________
6. Formation of dyad of cells. _______________________

Answer:

1. Synaptonemal complex – Zygotene
2. Recombination nodules-  Pachytene
3. Appearance/ activation of Pachytene Enzyme recombinase
4. Termination of chiasmata – Diakinesis
5. Interkinesis-  After Telophase – 1 / Before Meiosis – II
6. Formation of the dyad of cells – Telophase – 1 / After Meiosis – 1

Question 2. Mitosis results in the production of two cells that are similar to each other. What would be the consequence if each of the following irregularities occurs during mitosis?

1. The nuclear membrane fails to disintegrate.
2. Duplication of DNA does not occur.
3. Centromeres do not divida.
4. Cytokinesis does not occur.

Answer:

• If the nuclear membrane fails to disintegrate chromosomes cannot spread through the cytoplasm of the cell. Metaphase cannot take place.
• If Duplication of DNA does not occur equal number of chromosomes cannot enter into daughter cells, resulting in a variable number of chromosomes.
• If centromeres do not divide chromatids cannot move to opposite poles, then daughter cells have the same chromosome number with two chromatids.
• If cytokinesis does not occur then after cell division each cell contains two nuclei. Resulting in multinucleate condition.

Question 3. Comment on the statement “Meiosis enables the conservation of specific chromosome number of each species even though the process per second, results in a reduction of chromosome number.
Answer:

• Meiosis is the mechanism, by which chromosome number is reduced to half in sexually reproducing organisms.
• Enzyme recombinase
• Meiosis produces 4 haploid daughter cells (sex cells or gametes) from a diploid mother cell.
• Fertilization or union of sex cells again gives rise to diploid (2n) organisms.
• So, Meiosis is the mechanism, by which the conservation of the specific chromosome number of each species is achieved across generations.
• It also increases the genetic variability in the population of organisms from one generation to the next, which leads to evolution.

Question 4. How does cytokinesis in plant cells differ from that in animal cells?
Answer:

• Cytokinesis refers to the division of a mother cell into 2 daughter cells.
• This occurs after the Karyokinesis, the division of a mother nucleus into 2 daughter nuclei.
• In an animal cell, cytokinesis is achieved by the appearance of a furrow in the plasma membrane.
• The furrow gradually deepens and ultimately joins in the center, dividing the cell cytoplasm into two.
• Plant cells are enclosed by a relatively inextensible (rigid) cell wall.
• So in those cells, wall formation starts in the center of the cell and grows outward to meet the existing lateral walls.

Question 5. Which division is necessary to maintain constant chromosome number in all body cells of multicellular organisms and why?
Answer:

• Cell division Meiosis is necessary to maintain constant chromosome numbers in all body cells of multicellular organisms.
• The reason is mitosis divides and forms two daughter cells which are similar to the parent cell.
• The chromosome number remains constant in all the cells.
• Growth occurs due to mitosis.
• Mitosis also helps in cell repair and growth.

Question 6. Though redundantly described as a resting phase, the interphase does not involve rest. Comment.
Answer:

In the cell cycle, the stage at which the nucleus is not in a state of division is called interphase. It occurs between two successive divisions. During interphase, the cell prepares for division by undergoing growth as well as DNA replication in an orderly manner, though considered as the resting phase.

Based on biochemical studies, interphase is subdivided into 3 stages :

1. G₁: phase,
2. S: phase, and
3. G₂ phase.

These are

1. G₁: phase: Cell increases in size, RNA and proteins are synthesized in large quantity
2. S phase: DNA replication occurs and its content increases to 4c from 2c.
3. G₂ phase: Synthesis of proteins and RNA is continued. Various cell Organelles are newly synthesized. The proteins and energy pools associated with the structure and movement of chromosomes are established.

Important Long Answer Questions On Cell Cycle and Cell Division Class 11 Karnataka Board

Question 1. Discuss the statement – Telophase is the reverse of prophase.
Answer:

• The changes occurring in telophase are almost reversed to those that take place in prophase.
• The daughter chromosomes reach opposite poles.
• These daughter chromosomes lengthen and their visibility decreases due to decondensation of chromatin. The kinetochore fibers disappear.
• The nuclear membrane reappears. Nucleolus, Golgi complex, and ER reform.
• Thus at the end of telophase, two independent daughter nuclei are organized in the same mother cell.

Telephone:

Karnataka Board Chapter 10 Cell Cycle and Cell Division Solutions

Question 2. What are the various stages of meiotic prophase – 1 ? Enumerate the chromosomal events during each stage.
Answer:

Meiotic prophase I is longer and more complex when compared to the prophase of mitosis.

Prophase 1 is divided into 5 substages. They are

1. Leptotene
2. Zygotene
3. Pachytene
4. Diplotene
5. Diakinesis.

1. Leptotene

: Nucleus enlarges in size. Chromosomes are visible. They are long and slender.

2. Zygotene:

• Homologous chromosomes attract each other and form pairs. These are called bivalents.
• The process of pairing is called synapsis.
• Electron micrographs of this stage indicate that chromosome synapsis is accompanied by the formation of a complex structure called synaptonemal complex

3. Pachytene: It is the most significant substage of Meiosis I.

• Each chromosome divides into two chromatids. Thus in each bivalent, 4 chromatids can be seen. These are called pachytene tetrads.
• In a bivalent, chromatids of the same chromosome are called sister chromatids and those of two different chromosomes are called non-sister chromatids.
• The Pachytene stage Is characterized by the appearance of recombination nodules, the sites at which crossing over occurs between non-sister chromatids,
• The non-sister chromatids exchange their parts mutually at one or two or more places. Such points where the non-sister chromatids physically contact each other are called chiasmatAnswer: Chiasmata appear as X – shaped structures
• Crossing over is also an enzyme-mediated process and the enzyme involved is called recombinase.’
• By the end of pachytene, recombination between homologous chromosomes is completed leaving the chromosome linked at the side of crossing one.

4. Diplotene:

The beginning of diplotene is recognized by the dissolution of the synaptonemal complex and the tendency of the homologous chromosomes of the bivalent to separate from each other except at the site of charismata.

5. Diakinesis:

• Charismata moves toward the ends of chromosomes. This is called terminalisation.
• Bivalents become very thick and short.
• The nucleolus begins to disappear.
• The nuclear membrane disappears.
• Chromosomes are released into the cytoplasm.

Question 3. Differentiate between the events of mitosis and meiosis
Answer:

Differentiate between the events of mitosis and meiosis:

Class 11 Biology Cell Cycle and Cell Division Questions 

Question 4. Write a brief note on the following :

1. Synaptonemal complex
2. Metaphase plate

Answer:

1. Synaptonemal complex:

During the heptotene of prophase I, chromosomes start pairing together and this process of association is called synapsis.

1. Such paired chromosomes are called homologous chromosomes.
2. Electron micrographs of this stage indicate that chromosome synapsis is accompanied by the formation of a complex structure called synaptonemal complex.
3. The complex formed by a pair of homologous synapsed homologous chromosomes is called a bivalent or a tetrad of chromatids.

2. Metaphase plate:

In Metaphase two important changes take place.

• Formation of bipolar spindle fibers and attach the same to the kinetochores of chromosomes.
• All the chromosomes lie at the equator.
• The plane of alignment of the chromosomes at metaphase is referred to as the metaphase plate or equatorial plate.

Question 5. Write briefly the significance of mitosis and meiosis in multicellular organisms.
Answer:

Significance of mitosis:

• Growth in organisms is caused by mitosis and it restores the surface or volume ratio of the cell.
• The daughter cells formed by mitosis are identical to the mother cell. Hence it is important in conserving the genetic integrity of the organism.
• In unicellular organisms, mitosis helps in reproduction.
• Mitosis helps in wound healing and regeneration of lost plant parts.
• Mitosis helps with grafting in vegetative reproduction.
• It maintains a constant number of chromosomes in all the cells of the body.

Significance of meiosis:

• It helps in the maintenance of a constant chromosome number from one generation to the next.
• Due to crossing over, genetic recombinations are caused which help in genetic variation and origin of new species and leads to evolution.

Question 6. An organism has two pairs of chromosomes (i.o., chromosome number = 4). Diagrammatically represent the chromosomal arrangement during different phases of meiosis – 2
Answer:

Karnataka Board Class 11 Biology The Unit Of Life Synopsis

Coll is the basic unit of life In all living organisms.

• Cytology Is the study of the structure and functions of cells and cell organelles.
• Cell theory was proposed by Schlelden and Schwann and later by Rudolf Virchow.
• Cells that have membrane-bound nuclei are called eukaryotic cells.
• In prokaryotic cells, genetic material is naked, not enveloped by a nuclear: membrane.
• The plasma membrane or cell membrane is lipoproteinaceous. Unit membrane (Sandwich model) and Fluid mosaic models explain the structure and properties of plasma membranes.
• Part of the protoplasm except the nucleus is called cytoplasm. It exhibits active movements. It shows a cytoskeleton formed of microtubules and microfilaments.

Plastids, mitochondria and ER are double-membraned cell organelles.

• Lysosomes, dictyosomes, glyoxisomes and peroxisomes are single membranes.
• Ribosomes are membranous.
• Plastids are of 2 types- Leucoplasts and Chromoplasts.
• Chloroplasts are green plastids concerned with photosynthesis.
• Mitochondria are also called ‘powerhouses of cells’. Cellular respiration occurs in these cell organelles.
• The endoplasmic reticulum consists of tubules, vesicles and cisternae. It is concerned with protein and lipid synthesis. It is an intracellular transportation channel.

Ribosomes are nucleoprotein particles. They are sites of protein synthesis. Golgi complex (dictyosomes) consists of cisternae, vacuoles and tubules. They help in the synthesis of cell wall materials and the formation of cell plates during cell division.

• Lysosomes are single membrane-bound organelles with enzymatic matrix. They help in intracellular digestion. They also cause. autolysis of cell contents (suicidal bags of cells).
• Peroxisomes are involved in photorespiration and oxidation of fatty acids.
• Glyoxysomes contain enzymes related to the glyoxalate cycle.
• Fluid-filled sacs of cells having sap bound by tonoplast are called vacuoles. A vacuole acts as a ‘storehouse of cells’ or ‘repository of cells’. It helps in the osmoregulatory processes of cells.
• The nucleus It dynamic centre of the cell or cell brain. It plays an important role In heredity.
• Chromosomes are composed of cells of DNA bound to basic proteins- histones.
• Choromatlds are vertical halves of a chromosome attached attached at the centromere.
• Based on the position of centromere chromosomes are 4 types- metacentric, submetacentric, acrocentric and telocentric.
• Chromosomes are the physical basis of heredity.

The Unit of Life Class 11 Very Short Question And Answers

Question 1 . What is the significance of vacuole in a plant cell?
Answer:

1. In plant cells, vacuole plays an important role in osmoregulation.
2. In some plant cells, vacuolar sap contains pigments like anthocyanin, which impart colour to the plant parts.

Question 2. What does ‘S’ refer to in the 70S & and 80S ribosomes?
Answer:

1. ‘S’ refers sedimentation coefficient (expressed in Svedburg unit)
2. It is indirectly a measure of density and size.

Question 3. Mention a single membrane-bound organelle which is rich in hydrolytic enzymes.
Answer:

1. Lysosomes.
2. They contain hydrolases capable of digesting carbohydrates, proteins, lipids and nucleic acids.

Class 11 Biology Chapter 8 The Unit of Life 

Question 4. What are gas vacuoles? State their functions.
Answer:

Gas vacuoles are inclusion bodies in the cytoplasm of Blue-green, purple and green photosynthetic bacteria. They are filled with air and help the bacteria to float on the surface of water.

Question 5. What is the function of a polysome?
Answer:

1. In prokaryotes, several ribosomes may attach to a single m RN A and form a chain called a polysome.
2. The ribosomes of a polysome translate the m RNA into proteins.

Question 6. What is the feature of a metacentric chromosome?
Answer:

1. The metacentric chromosome has a middle centromere
2. Hence this chromosome consists of two equal arms.

Question 7. What is referred to as a Satellite Chromosome?
Answer:

1. Satellite Chromosome: Chromosome with non-staining secondary constriction at a constant location.
2. This gives the appearance of a small fragment called the satellite

Question 8. What are microbodies? What do they contain?
Answer:

1. Peroxysomes and glyoxysomes called microbodies
2. Glyoxysomes contain enzymes of the glyoxylate cycle which convert stored lipids into carbohydrates. Peroxysomes contain enzymes which convert acids into carbohydrates

Question 9. What is middle lamella made of? What is Its functional significance?
Answer:

1. Middle lamella is made of calcium pectate.
2. It holds or glues the different neighbouring cells together.

Question 10. What is osmosis?
Answer:

• The movement of water by diffusion across the membrane is called Osmosis.
• In this process, water moves from a higher concentration to a lower concentration across the plasma membrane.

Question 11. Which part of the bacterial cell is targeted in gram staining?
Answer:

• Chemical composition of cell envelop.
• Bacteria that take up gram stain are called Gram-positive and those that do not are called Gram-negative.

Question 12. Which of the following is not correct?

1. Robert Brown discovered the cell.
2. Schleiden and Schwann formulated the cell theory.
3. Virchow explained that cells are formed from pre-existing cells.
4. A unicellular organism carries out its life activities within a single cell.

Answer: 1. Robert Brown discovered the cell – not correct.

Question 13. New cells generate from

1. Bacterial fermentation
2. Regeneration of old cells
3. Pre-existing cells
4. Abiotic materials

Answer:  3. Pre-existing cells

Class 11 Biology Chapter 8 The Unit of Life 

Question 14. Match the following.

Answer: 1- B, 2- C, 3- A

Question 15. Which of the following is correct?

1. Cells of all living organisms have a nucleus.
2. Both animal and plant cells have a well-defined cell wall.
3. In prokaryotes, there are no membrane-bound organelles.
4. Cells are formed de novo from abiotic materials.

Answer: 3. In prokaryotes, there are no membrane-bound organelles – correct.

Karnataka Board Solutions For Class 11 Biology Chapter 8 The Unit Of Life Short Question And Answers

Question 1. Discuss briefly the role of nucleolus in the cells actively involved in protein synthesis.
Answer:

• A spherical body is present in the nuclear matrix, the. nucleoplasm is called as nucleolus (plu. Nucleoli). It is not a membrane-bound structure.
• In some nuclei, one or more nucleoli may be present.
• It is a site for the active synthesis of ribosomal RNA.
• rRNA makes cell organelles ribosomes, the sites of protein synthesis, several ribosomes may attach with an mRNA to form a chain, referred to be polyribosomes (polysome.) The ribosomes of a polysome translate the mRNA into proteins.
• Larger and more numerous nucleoli are present in cells actively carrying out protein synthesis.

Question 2. Explain the association of carbohydrates to the plasma membrane and its significance.
Answer:

• The lipid component of the plasma membrane mainly consists of phosphoglycerides.
• Biochemical investigations revealed that the cell membranes also possess carbohydrates.
• Carbohydrates present outside the plasma membrane and are attached to extrinsic proteins, integral proteins and also hydrophilic (polar) heads of the lipids. They may be glycoproteins or glycolipids.

The Unit of Life key questions for Class 11

Question 3. Comment on the cartwheel structure of the centriole.
Answer:

• A centrosome is an organelle usually containing two cylindrical structures called centrioles.
• They are surrounded by amorphous pericentriolar materials.
• Both the centrioles in a centrosome lie perpendicular to each other in which each has an organisation like the cartwheel.
• They are made up of nine. evenly spaced peripheral fibrils of tubulin.
• Each of the peripheral fibrils is a triplet. The adjacent triplets are also linked.
• The central part of the centriole is also proteinaceous and called the hub, which is connected with tubules of the peripheral triplets by radial spokes made of protein.
• The centrioles form the basal body of the cilia or flagella, and the spindle fibres that give rise to spindle apparatus during cell division in animal cells.

Question 4. Briefly describe the cell theory.
Answer:

1. Cell theory was proposed by MJ. Schleiden, a German botanist and T. Schwann; a British zoologist.
2. The cell theory states that
   • The cell is the structural unit of all organisms.
   • The cell is the functional unit of all organisms.
   • R. Virchow proposed that new cells arise from pre-existing cells (Omnis cellular-cellula) or the parent cell.

Question 5. Differentiate between Rough Endoplasmic Reticulum (RER) and Smooth Endoplasmic Reticulum (SER).
Answer:

Differentiate between Rough Endoplasmic Reticulum (RER) and Smooth Endoplasmic Reticulum (SER):

Question 6. Give the biochemical composition of the plasma membrane. How are lipid molecules arranged in the membrane?
Answer:

The biochemical composition of the plasma membrane is lipids, proteins and carbohydrates. In the membrane lipids are arranged in a bilayer.

• Within the membrane lipids are arranged with the polar (hydrophilic) head towards the outer side.
• This ensures that the non-polar tail of saturated hydrocarbons is protected from the aqueous environment.
• The Fluid Mosaic Model was proposed by Singer and Nicolson. It is the most widely accepted model.
• They described the cell membrane as “Protein icebergs in a sea of lipids”.
• According to this model, lipids are quasi-fluid. This enables lateral movement of proteins within the overall bilayer.

Question 7. What are plasmids? Describe their role in bacteria.
Answer:

• Small circular DNA molecules found outside genomic DNA in many Bacteria are called plasmids.
• The plasmid DNA confers certain unique phenotypic characteristics such as resistance to antibiotics in bacteria.
• Plasmid DNA is also useful to monitor bacterial transformation with foreign DNA.

Question 8. What are histones? What are their functions?
Answer:

Basic proteins associated with DNA In eukaryotes are called Histones.

• A typical nucleosome contains 200 bt of DNA double helix wrapped (2 turns) around a core of histone octamer having 2 copies each of 4 types of histone proteins (H2A, H2B, H3 and H4).
• The H1 histone molecule lies outside the nucleosome core and seals the 2 turns of DNA by binding at the point where DNA enters and leaves the core.
• The association between negatively charged DNA and positively charged histones allows for meaningful DNA packaging inside the nucleus.

Question 9. What is a Cytoskeleton? What functions is it involved in?
Answer:

An elaborate network of filamentous proteinaceous structures present in the cytoplasm is collectively referred to as the cytoskeleton.

• Eukaryotic cells contain three major components of the cytoskeleton- namely microfilaments, intermediate filaments and microtubules.
• The cytoskeleton in a cell is involved in many functions such as mechanical support, maintenance of cell shape, cell motility, intracellular transport, signalling across the cell and karyokinesis (movement of chromosomes during cell division).

Question 10. What is an endomembrane system? What cell organelles are not included in it? Why?
Answer:

Each of the membranous organelles is distinct in terms of its structure and function.

• Many of these membranous organelles are together considered an endomembrane system because their functions are coordinated.
• The endomembrane system includes the endoplasmic reticulum (ER), Golgi complex, lysosomes and vacuoles.
• Since the functions of mitochondria, chloroplast and peroxisomes are not coordinated with the above components, these are not considered as part of the endomembrane system.

Question 11. Distinguish between active transport and passive transport.
Answer:

• The molecules that move across the membrane without any requirement of energy is called passive transport.
• A few ions or molecules are transported across the membrane through its carrier proteins against their concentration gradient, i.e., from lower to higher concentration.
• Such a transport is an energy-dependent process, in which ATP is utilised and it is called active transport.

Example:  Na⁺/K⁺ pump.

Karnataka Board Class 11 Biology Chapter 8 

Question 12. What are mesosomes? What do they help in plasma?
Answer:

Plasma membrane Infoldings In some bacteria are called mesosomes.

• These special membranous extensions are in the form of vesicles, tubules and lamellae.
• Mesosomes help in cell wall formation, DNA replication and its distribution to daughter cells.
• They also help in respiration, secretion, and processes, to increase the surface area of the plasma membrane (helps in the absorption of nutrients) and enzymatic content.

Question 13. What are nucleosomes? What are they made of?
Answer:

• Chromatin appears as beads on a string. The beads are known as nucleosomes. A typical nucleosome contains 200 bp of
• DNA double helix wrapped (two turns) around a core of histone octamer having two copies ofeach of four types of histone proteins viz., H2A, H2B, H3 and H4.

Question 14. How do neutral solutes move across the plasma membrane? Can the polar molecules also move across it in the same way? If not, then how are these transported across the membrane?
Answer:

Neutral solutes move across the plasma membrane using diffusion along the concentration gradient.

• It moves from higher to lower concentration.
• No, the polar molecule cannot move across it in the same way.
• Polar molecules require a carrier protein of the membrane to facilitate their transport across the membrane.
• Some ions or molecules are transported across the membrane against their concentration gradient, which is an energy-dependent process. It is called active transport. In active transport, ATP is utilised.

Question 15. What are the characteristics of a prokaryotic cell?
Answer:

Prokaryotic cell organisation is fundamentally similar.

• Prokaryote shows a wide variety of shapes and functions.
• All prokaryotic cells have a cell wall surrounding the cell membrane.
• The fluid matrix filling the cell is the cytoplasm.
• There is no well-defined nucleus.
• The genetic material is naked, which means not enveloped by a nuclear membrane.
• In addition to the genomic DNA (circular DNA), many bacteria have small circular DNA outside the genomic DNA. These smaller DNAs are called plasmids.
• No organelles like in eukaryotes are found except in ribosomes.
• A specialized differentiated form of the cell membrane called mesosome is a characteristic of prokaryotic cells.
• It is essentially an infolding of the cell membrane.

Question 16. Multicellular organisms have division of labour. Explain.
Answer:

• Multicellular organisms have numerous cells.
• The cells in multicellular organisms originate from the division of the single-celled zygote.
• Newly formed cells are specialised to perform specific functions and a division of labour is established between these cells which co-exist in the body.
• Specialization of cells into tissues, organs and organ systems is advantageous for multicellular organisms.
• Different functions are carried out by different groups of cells in an organism.
• This is known as division of labour.

Question 17. The cell is the basic unit of life. Discuss in brief.
Answer:

• All life begins as a single cell.
• A cell is a unit of structure and function. Unicellular organisms complete their entire life cycle as a single cell.
• In multicellular organisms, cells are grouped into tissues, tissues into organs and organs into organ systems. So cell is a basic unit of every small or complex organism.
• Each cell is made up of several organelles Just like the one carried by different organ systems.
• Thus all the life activities of an organism are present in miniature form In every cell of Its body.

Question 18. What are nuclear pores? State their function.
Answer:

• At several places, the nuclear envelope is interrupted by minute pores which are formed by the fusion of its two membranes.
• These are called nuclear pores. A nuclear pore has a complex structure.

Nuclear pores Function:

The nuclear pores are the passage through which the movement of RNA and protein molecules takes place in both directions between the nucleus and the cytoplasm.

Question 19. Both lysosomes and vacuoles are endomembrane structures, yet they differ in terms of their functions. Comment.
Answer:

• Both lysosomes and vacuoles are endomembrane structures. Yet they differ in terms of their function because they contain different materials.
• The isolated lysosomal vesicles are very rich in almost all types of hydrolytic enzymes such as lipase, protease, and carbohydrates.
• These enzymes can digest carbohydrates, proteins, lipids and nucleic acids.
• Vacuoles contain water sap, excretory products etc. In
• Amoeba, conctratile vacuole is important for excretion. In plants, it plays an important role in osmoregulation.
• Thus though lysosomes and vacuoles are endomembrane, they are not similar in structure and function.

Question 20. Briefly give the contribution of the following scientists in formulating the cell theory.

1. Rudolf Virchow
2. Schleiden and Schwann

Answer:

1. Rudolf Virchow :

First explained that cells divide and new cells are formed from pre-existing cells (Omnis cellula-e cellula). He modified the hypothesis of Schleiden and Schwann to give the cell theory. Cell theory is

1. All living organisms are composed of cells and products of cells.
2. All cells arise from pre-existing cells.

2. Schleiden and Schwann:

Schleiden, a German botanist, examined a large number of plants and observed that all plants are composed of different kinds of cells which form the tissues of the plant

• Schwann, a British zoologist, studied different types of animals and reported that cells had a thin outer layer which is today known as a plasma membrane.
• He also concluded, based on his studies on plant tissue, that the presence of a cell wall is a unique characteristic of plant cells. wall Is a unique character of plant cells,
• Based on this Schwann proposed the hypothesis that the bodies of animals and plants are composed of cells and products of cells.

Question 21. Is extra dynamic DNA present in prokaryotes and eukaryotes? If YOB, indicate their location In both the types of organisms.
Answer:

1. Yes.
2. In prokaryotes, in addition to the genomic DNA (single chromosome / circular DNA), many bacteria have small circular DNA outside the genomic DNA. These smaller DNAs are called plasmids.
3. In Eukaryotes extra genomic DNA is present in mitochondria and chloroplast. The nucleolus has little amount of DNA.

Question 22. Structure finds function or a correlatable In living organisms. Can you justify this by diking plasma membrane as an example?
Answer:

• The structure of the plasma membrane is similar in all organisms- ranging from unicellular prokaryotes to multicellular eukaryotes.
• The plasma membrane in all organisms is made of the lipid bilayer. The polar (hydrophilic) heads of lipids are faced towards the outside and hydrophilic tails are faced towards the inside.
• The function of the plasma membrane as a semi-permeable membrane is also similar in all living organisms.
• Neutral solutes and solvents like water move across the plasma membrane passively according to their concentration gradient.
• Polar molecules like ions move across the plasma membrane with the help of carrier proteins against their concentration gradient. It is called active transport.

Question 23. What is a mesosome in a prokaryotic cell? Mention the functions that it performs.
Answer:

The plasma membrane is made up of lipids and proteins.

• A mesosome is a special membranous structure which is formed by the extensions of the plasma membrane into the cell.
• These extensions are in the form of vesicles, tubules and lamellae.
• They help In cell wall formation, DNA replication and Its distribution to daughter cells.
• They also help in respiration, and secretion processes to increase the surface area of plasma membrane and enzymatic content.

Question 24. How do neutral solutes move across the plasma membrane? Can the polar molecules also move across it in the same way? If not, then how are these transported across the membrane?
Answer:

• Neutral solute may move across the membrane by the process of simple diffusion along the concentration gradient i.e., from higher concentration to lower concentration.
• Polar molecules require carrier proteins of the membrane to facilitate their transport across the membrane.
• In active transport, a few ions or molecules

Example: Na⁺/ K⁺ pumps are transported across the membrane by carrier proteins against their concentration gradient (i.e. from lower to higher concentration) with the utilization of ATP.

Class 11 Biology The Unit Of Life Long Question And Answers

Question 1. What structural and functional attributes must a cell have to be called a living cell?
Answer:

• The cell which has a nucleus is called a living cell. It was first observed by Robert Brown.
• The cell in which the nucleus is absent is called a dead cell.
• The nucleus controls and regulates the function of all the cell organelles. It is, therefore, referred to as the dynamic centre of the cell or master control of the cell or cell brain.
• Nucleus Involves In Heridltary.
• Nucleus plays an important role In reproduction in unicellular organisms.

Cytoplasm:

Cytoplasm is a semi-fluid matrix. It occupies the volume of the cell.

• Cytoplasm is the main area of cellular activities in both plant and animal cells.
• Various chemical reactions occur in it to keep the cell in a living state.

Cell organelles:

The cytoplasm shows several membrane-bound structures called cell organelles which perform different functions and keep the cell in a dynamic state.

• Cell organelles are endoplasmic. reticulum (ER), the Golgi complex, lysosomes, mitochondria, plastids, microhardness and vacuoles
• In prokaryotic cells membrane-bound cell organelles are absent.

Ribosomes:

• Ribosomes are considered as smallest cell organelle in the cells.
• Ribosomes are not bounded by a definite unit membrane within the cell
• Ribosomes are called protein factories as they are important in protein synthesis.

Question 2. Eukaryotic cells have organelles which may
Answer:

1. Not be bound by a membrane
2. Bound by a single membrane
3. Bound by a double membrane

Group the various sub-cellular organelles into these three categories.
Answer:

Eukaryotic cells have organelles which may:

1. Not being bound by a membrane are Ribosomes.
2. Bound by a single membrane are lysosomes, vacuoles, microbodies (Peroxysomes and Glyoxysomes)
3. Bound by a double membrane are the Endoplasmic reticulum, Golgi bodies, mitochondria, chloroplast, and nucleus.

Question 3. The genomic content of the nucleus is constant for a given species whereas the extra chromosomal DNA is found to be variable for the members of a population. Explain.
Answer:

• For a given species the genomic content of the nucleus is constant to maintain specificity and stability.
• Some bacteria have extrachromosomal DNA called plasmids.
• They can exist independently in the cytoplasm or may be integrated with the chromosome among
• The plasmids can render bacteria drug-resistant, give them pathways and make them pathogenic.
• The presence of DNA in the chloroplast and mitochondria helps in self-duplication,
• Hence both chloroplast and mitochondria are called new metabolic semi-autonomous organelles.

Question 4. Justify the statement. “Mitochondria are powerhouses of the cell wall ”
Answer:

• Mitochondria occur In all eukaryotic cells.
• Mitochondria possess a double membrane envelope. Two unit membranes are separated by per mitochondrial space.
• The outer membrane is smooth. The inner membrane shows invaginations called cristae.
• The inner space is filled with a fluid matrix.
• Matrix consists of 70S ribosomes, circular DNA and RNA. The matrix also comprises respiratory enzymes.
• Many stalked particles present on the surface of cristae are called FQ- Fx particles.
• Krebs cycle of respiration occurs in the matrix and electron transport takes place in cristae.
• Mitochondria are concerned with cellular respiration. Food materials are oxidised and potential energy is converted into kinetic energy.
• It is stored in the form of adenosine triphosphate (ATP). So mitochondria are called powerhouses of the

Structure of mitochondrion (Longitudinal section):

Question 5. Is there a species-specific or region-specific type of plastids? How does one distinguish one from the other?
Answer:

Plastids bear specific pigments, thus imparting specific colours to the part of the plant which possesses them.

Based on the type of pigments plastids can be classified into chloroplasts, chromoplasts and leucoplasts:

1. Chloroplasts: They contain chlorophyll and carotenoid pigments which are responsible for photosynthesis.
2. Chromoplasts: In chromoplasts soluble carotenoid pigments like carotene, xanthophylls and others are present. This gives the part of the plant a yellow, orange or red colour.
3. Leucoplasts: They are colourless plastids of varied shapes and sizes with stored nutrients.
   • Amyloplasts store carbohydrates (starch)
     • Example: Potato
   • Elaioplasts Store oils and fats
   • Aleutoplasts store proteins.

Question 6. Write the functions of the following.

1. Centromere 
2. Cell wall
3. Smooth ER
4. Golgi Apparatus
5. Centrioles

Answer:

1. Centromere :

• Every chromosome has a centromere. On the sides of the centromere, disc-shaped structures called kinetochores are present.
• These are the sites of implementation of the microtubules of spindle fibres.
• During anaphase (cell division) based on the position of the centromere, chromosomes exhibit V, L, J and I shapes during their movement towards opposite poles.

2. Cell wall functions:

1. The cell wall protects the protoplast.
2. It gives a definite shape to the cells and provides mechanical strength.
3. Cell Wallis permeable in nature and allow the substances to pass through.

3. Smooth ER:

• Smooth ER is the major site for the synthesis of lipids.
• In animal cells, lipid-like steroidal hormones are synthesized in SER.

4. Golgi Apparatus functions are:

• It performs the function of packaging materials to be delivered either to the intra-cellular targets or secreted outside the cell.
• Several proteins synthesised by ribosomes are modified in the cisternal of the Golgi apparatus before they are released.
• It is an important site for the formation of glycoproteins and glycolipids.
• In plants, the Golgi complex is involved in synthesising cell wall materials.

It is important in “ceil plate formation” during cell division.

5. Centrlole function:

• It forms the basal body of cilia or flagella.
• It forms spindle fibres that give rise to spindle apparatus during cell division in animal cells.

Question 7. Are the different types of plastids interchangeable? If yes, give examples where they are getting converted from one type to another.
Answer:

• Yes, plastids are interchangeable.
• During various stages of growth, the plastids change their colour from one type. to other.
•  For instance, in potatoes when tubers are exposed to air, leucoplasts convert into chloroplasts.
• In tomatoes and chillies, the Ovaries contain leucoplasts, which change into chloroplasts after fertilisation and in ripe condition, the chloroplasts are transformed into chromoplasts.
• Chloroplasts can be seen in the petals which are green initially but later become coloured.

Question 8. Describe the structure of the following with the help of labelled diagrams.

1. Nucleus
2. Centrosome
3. Nucleus

Answer:

• The nucleus was first described by Robert Brown.
• The nucleus consists of highly extended and elaborate nucleoprotein fibres called chromatin, nuclear matrix and spherical bodies called nucleoli.
• The nuclear envelope consists of two membranes with a space between them called the perinuclear space.
• The outer membrane is continuous with the endoplasmic reticulum and also bears ribosomes on it.
• At several places, the nuclear envelope is interrupted by minute pores, which are formed by the fusion of its two membranes.
• The nuclear pore establishes a contact between nucleoplasm and cytoplasm.
• The nuclear matrix or the nucleoplasm contains nucleolus and chromatin.
• Nucleoli are spherical structures present in the nucleoplasm.
• The content of nucleolus is continuous with the rest of the nucleoplasm as it is not a membrane-bound structure.
• The nucleolus is a site for active ribosomal RNA synthesis. Numerous nucleoli carry out protein synthesis.

Structure of nucleus:

2. Centrosome :

• A centrosome is an organelle usually containing two cylindrical structures called centrioles.
• They are surrounded by amorphous periventricular materials.
• Both the centrioles in the centrosome lie perpendicular to each other in each has an organisation like a cartwheel.
• They are made up of nine evenly-spaced peripheral fibrils of tubulin.
• Each of the peripheral fibrils is a triplet.
• The adjacent triplets are also linked.
• The hub of the centriole is connected with tubules of the peripheral triplets by radial spokes made of protein.

Diagrammatic representation of internal structure:

Question 9. What in centromere? How does the position of the centromere form the basis of the classification of chromosomes? Support; You answer with a diagram showing the position of the centromere on different types of chromosomes.
Answer:

1. The region of the chromosome where two chromatids are held together at a point along their length is called primary constriction or centromere.
2. Two disc-like structures present on either side of the centromere are known as kinetochores.

Based on centromere position monocentric chromosomes are 4 types :

1. Metacentric: The centromere is present in the middle point of the chromosome. Both arms are equal in length. Chromosome appears in a V shape during anaphase.
2. Submetacentric: Centromere is slightly away from the middle point of the chromosome and both arms are unequal in length. Chromosome appears in an L shape during anaphase.
3. Acrocentric: Centromere is present towards one side. One arm is very long and the other arm is very short. Chromosome appears in a T shape during anaphase.
4. Telocentric: Centromere is present at the end of the arm. Only one arm is present. Chromosome appears in a T shape during anaphase.

Question 10. Name two cell-organelles that are double membrane-bound. What are the characteristics of these two organelles? State their functions and draw labelled diagrams of both. 
Answer:

1. Chloroplast

Chloroplast is the cell organelle which contains chlorophyll pigment.

• Chloroplasts are double membrane-bound structures.
• If the two membranes, the inner membrane is relatively less permeable.
• The inner space of chloroplast is filled with a colourless matrix called stroma.
• Flattened sacs called thylakoid mo are present In the stroma
• The Lakolds arc is arranged as a pile of coins called grana
• Thylakoids enclose space called lumen
• Lumen contain pigments

Chloroplast Function:

• Stroma contains enzymes required for the synthesis of carbohydrates and proteins
• Chloroplasts are photosynthetic in function.

 A sectional view of Chloroplast:

2. Mitochondria

• Mitochondria  is also called the powerhouses of the cell
• Mitochondria are double membrane-bound structures.
• Mitochondria is sausage shape or cylindroma;
• Each mitochondrion is a double membrane-bound structure with outer and inner membranes.
• Structure of Mitochondrion (Longitudinal Section)
• The outer membrane is smooth. The inner membrane divides the lumen into the outer compartment and inner compartment.
• The inner compartment is filled with a matrix.
• The inner membrane forms several infoldings called cristae towards the matrix

Mitochondria Function:

• Mitochondria are the sites of aerobic respiration. They produce cellular energy in the form of ATP. hence they are called powerhouses of the cell.
• Matrix possesses a single circular DNA molecule, a few RNA molecules, ribosome (70S) required for protein synthesis.

Diversity of Living World Class 11 Biology Synopsis

• Biology is the science of life and living processes.
• Cells of an organism are the ‘Basic Units’ of ‘structure’ and ‘function’.
• The fundamental source of energy for all biological systems is the ‘Sun’.
• ‘ Diversity in living organisms comes from their ability to change.
• Evolution is the ‘Fundamental Organising Principle’ of life and it answers many questions about life and its complexity.
• The increase in complexity is right from the simple cellular level to the organism level followed by populations, communities, and ecosystem levels in the Biosphere.
• All the habitable zones of life on the earth constitute the Biosphere.
• Growth is one of the fundamental characteristics of living beings.
• ATP is the chief energy carrier for various reactions in living systems and it is appropriately described as the “Cellular Energy Currency”.
• + Lamarck (1809), a French Biologist coined the term ‘Biology’.
• So far over 1.25 million animal species have been identified and described.
• Carolus Linnaeus (1707 – 1788) Father of Taxonomy and Founder of Modern
• Systematics introduced the system of hierarchical classification.
• Three Domain classifications include Domain I – Bacteria, Domain ll.-Archaea,  Domain – III – Eukarya.
• Carolus Linnaeus popularised the “Binomial Nomenclature” in the 10th edition of his book “Systema Naturae”.
• Species is the ‘basic unit’ of classification. John Ray coined the term species.
• Buffon, in his book ‘Natural History’, proposed the idea of the evolution of species.
• “The Origin of Species” is a book by Charles Darwin.
• Dobzhansky introduced the concept of “Mendelian Population” while defining species. Biology
• Kingdom Animalia includes eukaryotic, multicellular heterotrophs.
• The variation of life at various levels of biological organization is termed as Biodiversity.
• The term biodiversity was popularized by the sociobiologist “Edward Wilson”.

Class 11 Biology Diversity of Living World Very Short Question And Answers

Question 1. Define the term metabolism. Give any one Example.
Answer: The total of all the chemical reactions occurring in the bodies of organisms constitute metabolism and it is a defining feature of all living organisms without exception.

Example: Photosynthesis and respiration.

Question 2. How do you differentiate between growth in a living organism and a nonliving object?
Answer: Growth in living beings is ‘growth from inside’ whereas growth in non-living things is by accumulating material on the surface.

Question 3. What is biogenesis?
Answer: ‘Life comes only from life and not from non-living substances’ is known as biogenesis.

Question 4. Define the term histology. What is it otherwise called?
Answer: Histology is the study of the microscopic structure of different tissues. This branch is also referred to as “Microanatomy”.

Class 11 Biology Diversity of Living World notes 

Question 5. Distinguish between embryology and ethology.
Answer:

1. Embryology deals with the study of events that lead to fertilization, cleavages, early growth, and differentiation of a zygote into an embryo.
2. The study of animal behavior based on the systematic observation, recording, and analysis of functions of animals, with special attention to ecological, physiological, and evolutionary aspects is called Ethology.

Question 6. ‘In a given area, remains of an animal that lived in the remote past are excavated for study. Which branch of science is it called?
Answer: Palaeontology, (specifically palaeozoology – study of fossils of animals)

Question 7. “Zoos are tools for classification” Explain.
Answer:

Zoos are the places where wild animals, taken out of their natural habitat, are placed in protected environments under human care. This enables us to study the various aspects of animal living. Thus it allows us to systematize the organism and position it in the animal world.

Question 8. Where and how do we preserve skeletons of animals, dry specimens, etc?
Answer: In Museums, animal specimens may also be preserved as dry specimens. Museums often have collections of skeletons of animals too.

Question 9. What In Trinominal nomenclature? Give Example
Answer:

The normal nomenclature Is the extension of the binominal system of nomenclature. This system permits the designation of subspecies with a three-worded name called Trinominal  Subspecies is a category below the level of species.

Example: Corvus splendens splendens.

Question 10. What is meant by tautonymy? Give two examples.
Answer:

The practice of naming animals, in which the generic name and species name are the same, is called tautonymy. So the name is called tautonym.

Example:  Naja naja (the Indian cobra), Axis axis (spotted deer).

Question 11. Differentiate between Protostomia and Deuterostomia.
Answer:

• Protostomia: The eumetazoans in which blastopore develops into the mouth are referred to as the protostomians.
  • Example: Annelida
• Deuterostomia: These are coelomates in which the anus is formed from or near the blastopore
  • Example: Echinodermata

Question 12. ‘Echinoderms are enterocoelomates’. Comment.
Answer:

Enterocoel is a true coelom formed from the archenteron. In phylum Echinodermata, the true coelom is formed from the primitive gut called archenteron. Hence Echinoderms are enterocoelomates.

Question 13. What does ICZN stand for?
Answer:

ICZN stands for International Code of Zoological Nomenclature.

Class 11 Biology Diversity of Living World Question And Answers 

Question 14. Give the names of any four protostomian phyla.
Answer:

Four protostomian phyla:

1. Platyhelminthes
2. Nematoda
3. Annelida
4. Arthropoda.

Question 15. Nematode is a protostomian but not a eucoelomate. Justify the statement.
Answer:

In Nematodes the blastopore becomes mouth and the group belongs to protostomia. However, the body cavity is not a true coelom as it is not lined by mesodermal epithelial layers. Their body cavity is a pseudocoel.

Question 16. What is ecological diversity? Mention the different types of ecological diversities.
Answer:

Diversity at the ecosystem level is called “Ecological diversity”. The different types of ecological diversities are Alpha, Beta, and Gamma diversities.

Question 17. Define species richness.
Answer:

Species richness in simple terms, it is the number of species per unit area. The more the number of species in an area the more is the species richness.

Question 18. Mention any two products of medical importance obtained from Neturo.
Answer:

Quinine (a drug for Malaria) is obtained from the bark of cinchona officinalis.

1. Vin blasting (anti-cancer drug) from Vinca
2. Digitalin from the ’fox glove’ plant (Digitalis purpurea).

Question 19. Invasion of an Alien species leads to Justify this with two examples.
Answer:

Nile perch introduced into Lake Victoria, in East Africa led to the extinction of 200 species of cichlid fish in the lake.

The illegal introduction of exotic African catfish, Clarias gariepinus, for aquaculture purposes, is posing a threat to the indigenous catfishes.

Question 20. Write the full form of IUCN. In which book threatened species enlisted.
Answer:

1. International Union for the Conservation of Nature and Natural Resources (IUCN)
2. All the threatened species are listed in the Red Data Books published by the IUCN.

Short Answer Questions For Class 11 Biology Diversity of Living World

Question 1. Explain the Phylogenetic system of biological classification.
Answer:

Carolus Linnaeus introduced the system of hierarchical classification. Phylogenetic system of biological classification (cladistic classification) . It is an evolutionary classification based on how a common ancestry was shared. Cladistic classification summarizes the ‘genetic distance’ between all species in the ‘phylogenetic tree’.

In cladistic classification characters such as analogous characters (Characters shared by a pair of organisms due to convergent evolution

• Example: Wings in sparrows and patagia (wing-like structures in flying squirrels)

And homologous characters (characters shared by a pair of organisms, inherited from a common ancestor

• Example:  Wings of sparrows and finches) are followed/ taken into consideration.

Ernst Haeckel introduced the method of representing phylogeny by ‘trees’ or branching diagrams.

Question 2. Explain the Monarchy  Classification 
Answer:

Linnaeus was the first taxonomist to establish a definite hierarchy of taxonomic categories called taxa (singular: taxon) like kingdom, class, order, genus, and species.

Haeckel introduced the taxon phylum. A species sometimes may have more subspecies, which shows some morphological variations (intra-specific variations). Taxonomic Categories: Nowadays the three-domain classification is followed.

CARL WOESE and co-workers observed that many prokaryotes previously classified under ‘Prokaryota/ Monera’ are more closely related to the ‘eukaryotes’ and classified them under a separate Domain the ARCHAEA. This type of study is called ‘MOLECULAR SYSTEMATICS’.

Now there is a general agreement on the

Three domestic classifications of the living organisms namely:

DOMAIN -1: BACTERIA

DOMAIN – 2: ARCHAEA, and

DOMAIN – 3: EUKARYA

Note: DOMAIN is a taxon higher than ‘Kingdom’

Question 3. What is meant by classification? Explain the need for classification.
Answer:

Need for classification:

• It is impossible to study all living organisms. So, it is necessary to devise some means to make this possible. This process is called ‘classification’.
• Classification is defined as the process by which anything is grouped into convenient categories based on some easily observable characteristics
• . The scientific term used for these categories is ‘TAXA’ (singular: taxon). Taxa can indicate categories at different levels

Example: Animalia (which includes multicellular animals), chordata, mammalia, etc., represent taxa at different levels.

Hence, based on characteristics, all living organisms can be classified into different taxa  This process of classification is called taxonomy.

Question 4. Define species. Explain the various aspects of ‘species’.
Answer:

Species:

Species is the ‘basic unit’ of classification. Species is a Latin word meaning ‘kind’ or ‘appearance’. John Ray in his book ‘Historia Generalis Plantarum’, used the term ‘species’ and described it based on common descent (origin from common ancestors) as a group of morphologically similar organisms.

Linnaeus considered species, in his book ‘Systema Nature‘, as the basic unit of classification.

Buffon’s biological concept of species explains that a species is an interbreeding group of similar individuals sharing the common ‘gene pool’, and producing fertile offspring.

Class 11 Biology Diversity of Living World

Species are considered as a group of individuals which are :

1. Reproductively isolated from the individuals of other species – a breeding unit.
2. Sharing the same ecological niche – An ecological unit.
3. Showing similarity in the karyotype – a genetic unit.
4. Having similar structure and functional characteristics – an evolutionary unit.
5. Species are dynamic.

Question 5. What is genetic diversity and what are the different types of genetic diversity
Answer:

Genetic diversity:

It Is the diversity of genes within In species, A single species may show high diversity at the genetic level over Its distributional range,

For example:

Rauwolfia vomitoria, a medicinal plant growing In the Himalayan ranges shows great genetic variation, which might be in terms of potency and concentration of the active chemical (reserpine extracted from It is used In treating high blood pressure) that the plant produces. India has more than 50,000 different strains of rice and 1,000 varieties of mangoes. Genetic diversity increases with environmental variability and is advantageous for its survival.

Question 6. What are the reasons for greater biodiversity in the tropics?
Answer:

Reasons for greater biodiversity in the tropics:

• Reason 1: Tropical latitudes have remained relatively undisturbed for millions of years and thus had a long ‘evolutionary time’. As long duration was available in this region for speciation, it led to the species diversification
• Reason 2: Tropical climates are relatively more constant and predictable than that of the temperate regions. Constant environment promotes niche specialization (how an organism responds and behaves with the environment and other organisms of its biotic community), and this leads to greater species diversity.
• Reason 3: Solar energy, resources like water, etc., are available in abundance in this region. This contributed to higher productivity in terms of food production, leading to greater diversity.

Question 7. What is the “evil quartet”?
Answer:

The following are the four major causes of accelerated rates of species extinction in the world. These causes are referred to as the evil quartet.

• Habitat loss and fragmentation: These are the most important reasons for the loss of biodiversity.
• Over-exploitation: When need turns to greed, it leads to over-exploitation.
• Invasion of Alien species: When Alien species are introduced into a habitat, they turn invasive and establish themselves at the cost of indigenous species.
• Co-extinctions: In an obligate association between a plant and an animal, if a plant becomes extinct, the animal also becomes extinct as seen in a parasitic and host association.

Question 8. Explain In brief “Biodiversity Hot Spots”
Answer:

Conservationists Identified certain regions by name ‘Biodiversity hot spots for maximum protection as they are characterized by very high levels of species richness & high degree of endemism.

By definition ‘Biodiversity hot spot’ Is a ‘Biogeographic Region’ with a significant reservoir of biodiversity that is under threat of extinction from humans. They are Earth’s biologically ‘richest’ and ‘most threatened’ terrestrial Ecoregions.

Biodiversity hot spots:

The concept of biodiversity originated by Norman Myers. There are about 34 biodiversity hot spots in the world.

As these regions are threatened by destruction, habitat loss is accelerated examples:

1. Western Ghats and
2. Srilanka
3. Indo Burma
4. Himalayas in India

Ecologically unique and biodiversity-rich regions are legally protected.

1. Biosphere Reserves – 14
2. National Parks – 90
3. Sanctuaries -448.

Question 9. Explain the ‘Rivet Popper” hypothesis.
Answer:

This hypothesis is mainly for a reason, what happens if we lose a few species?

Will it affect man’s life? Paul Ehrlich’s experiment ‘The RIVET POPPER’ hypothesis, taking an airplane as an ecosystem, explains how the removal of one by one ‘rivets’ (species of an ecosystem) of various parts can slowly damage the plane (ecosystem) – shows how important a ‘species’ is in the overall functioning of an ecosystem.

Removing a rivet from a seat or some other relatively minor important parts may not damage the plane, but the removal of a rivet from a part supporting the wing can result in a crash. Likewise, the removal of a critical species’ may affect the entire community and thus the entire ecosystem.

Question 10. Write short notes on In-situ conservation.
Answer:

In-situ conservation is the process of protecting an animal species in its natural habitat.

The following are the types:

1. Biosphere Reserves:

An area that is set aside, and minimally disturbed for the conservation of the resources of the biosphere is a ‘Biosphere reserve’. The latest biosphere reserve (17th biosphere reserve in India) is Seshachalam Hills.

2. National Parks:

A National Park is a natural habitat strictly reserved for the protection of natural life. National Parks, across the country, offer a fascinating diversity of terrain, flora, and fauna.

Some important National Parks in India are – Jim Corbett National Park (the first National Park in India located in Uttarakhand), Kaziranga National Park (Assam), Kasu Brahmananda Reddy National Park, Mahavir Harina Vanasthali National Park (Telangana), Keoladeo Ghana National Park (Rajasthan), etc.

3. Sanctuaries :

Specific endangered faunal species are well protected In wildlife sanctuaries which permit eco-tourism (as long as animal life is undisturbed). Some Important sanctuaries in India (AP) include – Koringa Sanctuary, Eturnagaram Sanctuary, and Papikondalu Sanctuary.

4. Sacred Groves:

• A smaller group of trees than a forest is called a grove.
• A grove of trees of special religious importance to a particular culture is called a sacred grove.
•  In these regions, all the trees of wildlife were venerated (respected) and given total protection.

 The following is a list of Sacred Groves in INDIA:

In Meghalaya, Sacred Groves are the last refuges for a large number of rare and threatened species