CBSE Sample Papers for Class 11 Biology Set 4 with Solutions

students must start practising the questions from CBSE Sample Papers for Class 11 Biology with Solutions Set 4 are designed as per the revised syllabus.

CBSE Sample Papers for Class 11 Biology Set 4 with Solutions

Time Allowed : 3 hours
Maximum Marks: 70

General Instructions :

1. All questions are compulsory.
2. The question paper has four sections: Section A, Section B, Section C and Section D. There are 27 questions in the question paper.
3. Sedion-A has 5 questions ofl mark each. Section-B has 7 questions of 2 marks each. Section-C has 12 questions of 3 marks each and Section-D has 3 questions of 5 marks each.
4. There is no overall choice. However, internal choices have been provided in some questions. A student has to attempt only one of the alternatives in such questions.
5. Wherever necessary, neat and properly labelled diagrams should be drawn.

Section – A

Direction (Qs. 1 & 2): In the below questions, the Assertions (A) and Reasons (R) have been put forward. Read both the statements and choose the correct option from the following:

Question 1.
Assertion (A): Both hexokinase and glucokinase require divalent cation Mg⁺⁺ or Mn⁺⁺
Reason (R): The divalent cations act as catalysts.
(A) Both A and R are true and R is the correct explanation of A.
(B) Both A and R are true but R is NOT the correct explanation of A.
(C) A is true but R is false.
(D) A is false but R is true.
Answer:
(B) Both A and R are true but R is NOT the correct explanation of A.
Explanation:
Both hexokinase and glucokinase require a divalent cation as Mg2+or Mn2+ that combines with ATP to form MgATP²⁺or MnATP²⁺ to participate as catalyst.

Question 2.
Assertion (A): Red algae contribute in producing coral reefs.
Reason (R): Some red algae secrete and deposit calcium carbonate over their walls.
(A) Both A and R are true and R is the correct explanation of A.
(B) Both A and R are true but R is NOT the correct explanation of A.
(C) A is true but R is false.
(D) A is false but R is true.
Answer:
(A) Both A and R are true and R is the correct explanation of A.
Explanation:
Red algae contribute in producing coral reefs as they secrete and deposit calcium carbonate over their walls. As for example, red algae coralline algae deposit CaCO₃ in their cell wall, coral reef is made of thin layers of CaCO₃.

Question 3.
The following substances are the excretory products in animals. Choose the least toxic form among them?
(A) Urea
(B) Uric acid
(C) Ammonia
(D) Carbon dioxide
Answer:
(B) Uric acid

Question 4.
A person suffers punctures in his chest cavity in an accident, without any damage to the lungs its effect could be:
(A) Reduced breathing rate
(B) Rapid increase in breathing rate
(C) No change in respiration
(D) Cessation of breathing
Answer:
(D) Cessation of breathing

Question 5.
Bryophytes require water in their habitat for
(A) filling archegonia for fertilisation.
(B) vegetative propagation.
(C) swimming of sperms to egg in archegonium.
(D) their homosporous nature.
Answer:
(C) swimming of sperms to egg in archegonium.

Section – B

Question 6.
What is heterospory? Briefly comment on its significance. Give two examples.
Answer:
Heterospory is the production of two kinds of spores and is the first step towards seed habit. Pteridophytes such as Selaginella, Salvinia and Marsilea produce two kinds of spores-microspores and macrospores.

Significance:

1. The mega and microspores germinate and then give rise to male and female gametophytes.
2. The female gametophyte is retained on the parent sporophyte for a variable period of time.
3.  The development of zygote into young embryo occurs within the female gametophyte. This step is said to be a precursor of seed habit as exhibited by gymnosperms and angiosperms

Question 7.
How annelids have receptors to sense the environment?
Answer:

1. Annelids have several receptors to sense light. Light receptors occur in clusters in polychaetes and leeches to sense light.
2. In earthworms, they are diffused, which can differentiate only between darkness and light.
3. Chemical and taste receptors are found in the fleshy lobe called prostomium.
4. Touch receptors are found all over the body. The cell membrane is composed of lipid bilayer of phospholipid molecules into which variety of globular proteins are embedded.

Question 8.
Explain the association of carbohydrate to the plasma membrane and its significance.
Answer:
Carbohydrates are associated with phospholipids or with peripheral proteins to form glycolipids and glycoproteins respectively. This helps in cell recognition. e.g., surface of RBC has carbohydrates arranged in branched chains. This difference in the arrangement give rise to different blood group antigens i.e., AB and O.

Question 9.
Draw a diagram to show the sigmoid growth curve and write the names of the three phases in it.
Answer:
Carbohydrates are associated with phospholipids or with peripheral proteins to form glycolipids and glycoproteins respectively. This helps in cell recognition. e.g., surface of RBC has carbohydrates arranged in branched chains.
This difference in the arrangement give rise to different blood group antigens i.e., AB and O.

Question 10
Maize grain is usually called a fruit and not a seed. Why?
OR
Mention the importance of trichomes and root hair for a plant.
Answer:
Maize grain is called fruit because, it develops from the ripened ovary, which contains ripened ovule. This fruit is called caryopsis, in which the pericarp is fused with the seed coat.
OR
Trichomes are hairs which are often found as epidermal outgrowths. The hairs of aerial parts may be unicellular or multicellular, branched or unbranched.

Functions:

1. They enclose stationary air and protect the plant organ against water loss and sudden fluctuation in atmospheric temperature.
2. In some plants, the hairs are glandular which secrete essential oil and provide characteristic odours to the plant. e.g., Citrus, Ocimum, etc.

Question 11.
Can there be DNA replication without cell division?
OR
(a) What is G₀ (quiescent phase) of cell cycle?
(b) What is the average cell cycle span for a mammalian cell?
Answer:
Yes. During cell division, the parent cell gets divided into two daughter cells. However, if there is repeated replication of DNA without any cell division, then this DNA keeps on accumulating inside the cell. This would increase the volume of the cell nucleus, thereby causing cell expansion. For example, in the salivary gland of Drosophila, the chromosomes undergo repeated DNA duplication without cell division.
OR
(a) G₀ or quiescent phase is the stage wherein cells remain metabolically active, but do not proliferate unless called to do so. Such cells are used for replacing the cells lost during injury.
(b) Average cell cycle span for a mammalian cell is approximately 24 hours.

Question 12.
Differentiate between peritubular capillaries and vasa recta?
Answer:
The fine capillary network around the renal tubule formed by the efferent arteriole emerging from the glomerulus are called peritubular capillaries. The U-shaped peritubular capillary that runs parallel to the henle’s loop is called vasa recta.

Section – C

Question 13.
Each of the following terms has some anatomical significance. What do these terms mean? Explain with the help of line diagrams.
(i) Plasmadesmoses/ Plasmodesmata
(ii) Middle lamella
(iii) Secondary wall
Answer:
(i) Plasmodesmata: These are cytoplasmic bridges between the two cells through the cell wall. They form a
protoplasmic continuum called symplast. It allows communication and transport between two neighbouring cells.

(ii) Middle lamella: It is a thin layer present in the cell wall mainly made up of calcium pectate. It performs the function of cementing between the two neighbouring cells.

(iii) Secondary wall: It is the non-extensible layer made up of hemicellulose fibres, in the cell wall of plant cells. It
provides ngiclitV to the cell waLl in plant cells.

Question 14.
Differentiate between anabolic and catabolic pathways. How are the pathways regulated?
Answer:
Difference between anabolic and catabolic pathways.

Anabolic pathways	Catabolic pathways
(i) Anabolic pathway is called anabolism.	Catabolic pathway is known as catabolism.
(ii) It consumes energy to make complex molecules like glucose.	It liberates energy by breaking the chemical bond. Glucose is broken down to release energy.
(iii) Example: Photosynthesis	Example: Cellular respiration.

Question 15.
What is cephalisation?
Answer:

1. The differentiation of a definite head at the anterior end is called cephalisation.
2. It involves the concentration of nervous tissue (brain) and sense organs in the head.
3. This arrangement is an advantageous adjustment with the environment, as the anterior end of the moving animal is the first to encounter changes in the area, it is entering.

Question 16.
Distinguish between a whale and a fish.
Answer:
Differences between whale and fish are:

Whale	Fish
(i) Whale is a mammal. The hair on its body are lost due to aquatic adaptation.	Scales are present over the body of fish. It belongs to Pisces.
(ii) Respires with the help of lungs only.	Respires by means of gills.
(iii) It is viviparous i.e., give birth to young ones.	It is oviparous i.e., lays eggs.
(iv) Females have mammary glands.	Mammary glands are absent in them.
(v) The forelimbs do not have claws and are flattened and modified into paddle-like flippers. The hindlimbs are ab sent in whales.	Limbs are absent. For locomotion, the fins are present.

Question 17.
What is cyanobacteria? State some characteristics of them with example.
Answer:
(i) They are also known as blue-green algae. They are found in a wide range of habitats where sufficient moisture and suitable temperature are present. They bloom in polluted water bodies.

(ii) They show different morphological forms. Some of them are unicellular (e.g., Chroococcus), some are colonial (e.g., Microcystis) and some are filamentous (e.g., Nostoc, Anabaena). Their colonies are generally surrounded by gelatinous sheaths.

(iii) Some of the cyanobacteria like Nostoc and Anabaena have special cells called heterocysts to fix atmospheric nitrogen.

(iv) Because of the presence of chlorophyll – a these organisms are photosynthetic autotrophs.

Question 18.
Briefly describe Photorespiration process.
Answer:
It is the light-dependent process of oxygenation of RuBP and release of carbon dioxide by photosynthetic organs of plants. Photorespiration decreases the rate of photosynthesis when oxygen concentration is increased from 2-3% to 21%. Presence of light and higher concentration of oxygen results in the binding of RubisCO enzyme with O₂ to form phosphoglyceric acid and phosphoglycolate.

RuBisCO + O₂ → PGA + phosphoglycolate

This pathway involves Chloroplast, Peroxisome and Mitochondria. Photorespiration does not occurs occur in C₄ plants.

Question 19.
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 by means of 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 20.
Thrombocytes are essential for coagulation of blood. Comment.
Answer:
Thrombocytes are also called platelets. When there is an injury, the blood platelets release certain chemicals which are called platelet factors. These factors help in coagulation of blood.

Question 21.
Explain three disorders of respiratory system.
Answer:
Disorder of Respiratory System
(i) Asthma: It is due to an allergic reaction to foreign particles that affect the respiratory tract. The symptoms include coughing, wheezing and difficulty in breathing. This is due to excess of mucus in wall of respiratory tract.

(ii) Emphysema: It is the inflation or abnormal distension of the bronchioles or alveolar sacs of lungs. This occurs due to destroying of septa between alveoli because of smoking and inhalation of other smokes. The exhalation becomes difficult and lung remains inflated.

(iii) Occupational Respiratory Disorders: Occurs due to occupation of individual. This is caused by inhalation of gas, fumes or dust present in the surrounding of workplace. This includes Silicosis, Asbestosis due to exposure of silica and asbestos. The symptom includes proliferation of fibrous connective tissue of upper part of lung causing inflammation.

(iv) Pneumonia: It is acute infection or inflammation of the alveoli of the lungs due to bacterium Streptococcus
pneumonia. Alveoli become acutely inflamed and most of air space of the alveoli is filled with fluid and dead white blood corpuscles limiting gaseous exchange. (Any three)

Question 22.
Describe glomerular filtration in human nephrons.
OR
What is ADH? What are its functions?
Answer:
The glomerular capillaries are narrower than the afferent renal arterioles, therefore the blood pressure in the glomerular capillaries becomes very high and there is continuous process of ultra-filtration through the semi-permeable glomerular capillaries.

Filtration of blood occurs through three layers:
(i) The endothelium of glomerular blood vessels.
(ii) The epithelium of Bowman’s capsule and
(iii) The basement membrane between the two layers. The epithelial cells of Bowman’s capsule called podocytes are arranged intricately so as to leave minute spaces called filtration slits. The glomerular filtrate and blood plasma are similar except that glomerular filtrate does not have proteins and fats.
OR
Antidiuretic hormone (ADH) is one of the hormones that efficiently monitors and regulates the functioning of the kidneys. The Antidiuretic hormone released from the posterior pituitary, prevents wide swings in water balance, helping to avoid dehydration or water overload. ADH facilitates reabsorption of water by the distal parts of the kidney tubules and thereby prevents diuresis.

Question 23.
What is meant by the statement “aerobic respiration is more efficient.”?
OR
Anaerobic respiration cannot continue for a long in higher organisms. Why?
Answer:
Anaerobic respiration cannot continue for a long in higher organisms because of:

1. low yield of energy,
2. decomposition of large number of substrates so that little is left for growth and repairs,
3. toxic effect of end products in higher concentration,
4. inhibition of a number of physiological processes linked with aerobic respiration.

Question 24.
Suppose there were plants that had a high concentration of chlorophyll b, but lacked chlorophyll a, would it carry out photosynthesis? Then why do plants have chlorophyll b and other accessory pigments?
Answer:
Chlorophyll ” molecules act as antenna molecules. They get excited by absorbing light and emit electrons during cyclic and non-cyclic photophosphorylation. They form the reaction centres for both photosystems I and II. Therefore, chlorophyll ‘a’ is essential for photosynthesis. Chlorophyll ‘b’ and other photosynthetic pigments such as carotenoids and xanthophylls, on the other hand act as accessory pigments. Their role is to absorb energy and transfer it to chlorophyll ‘a’. Carotenoids and xanthophylls also protect the chlorophyll molecule from photo-oxidation. If any plant lack chlorophyll ‘a’ and has a high concentration of chlorophyll ‘b’, then this plant would not undergo photosynthesis.

Section – D

Question 25.
Read the following and answer any four questions from (i) to (v) given below: 5×1 = 5
Renin-Angiotensin System A fall in glomerular blood flow or glomerular blood pressure or GFR can activate the JG cells to release renin. Renin converts angiotensinogen in blood to angiotensin I and further to angiotensin II. Angiotensinogen renin Angiotensin I → Angiotensin II Angiotensin II increases the glomerular blood pressure and thereby GFR. Angiotensin II also activates the release of Aldosterone which causes reabsorption of sodium ion and water from the distal parts of the tubule.

This also causes an increase in blood pressure and GFR. This complex mechanism is called as the Renin-Angiotensin mechanism. Atrial Natriuretic Factor (ANF)releases due to an increase in blood flow to the atria of the heart. ANF can cause vasodilation (dilation of blood vessels) and thereby decrease the blood pressure. ANF mechanism, therefore, inhibits renin-angiotensin mechanism.

(i) The full form of GFR is ……………
(A) Glomerular filtration renin
(B) Growth filtration rate
(C) Glomerular filtration rate
(D) Glomerular filter rate
Answer:
(C) Glomerular filtration rate

(ii) The JGA plays a complex role.
(A) vasoconstrictor
(B) regulatory
(C) vasodilator
(D) filter
Answer:
(B) regulatory
Explanation: Juxtaglomerular apparatus play a complex regulatory role.

(iii) Angiotensin II activates the gland to release Aldosterone.
(A) Pineal
(B) Adrenal cortex
(C) Adrenal medulla
(D) Thyroid
Answer:
(B) Adrenal cortex
Explanation:
Angiotensin II activates the Adrenal cortex gland to release Aldosterone.

(iv) The actively transported substances during reabsorption of GFR is/are
(A) nitrogenous wastes
(B) glucose and amino acid
(C) nitrogenous wastes and water
(D) glucose, amino acid and sodium
Answer:
(D) glucose, amino acid and sodium

(v) We can produce a concentrated/ dilute urine. This is facilitated by a special mechanism. Identify the mechanism.
I. Countercurrent mechanism in Henle’s loop/Vasa recta
II. Reabsorption from Collecting Duct
III. Reabsorption/ Secretion in DCT
IV. Reabsorption from PCT
Choose from below the correct alternative.
(A) only I is true
(B) I and IV are true
(C) III and II are true
(D) I and III are true
Answer:
(A) only I is true

Question 26.
What is a flower? Describe the parts of a typical angiosperm flower.
Answer:
The flower can be defined as a modified shoot bearing nodes and modified floral leaves. Flowers exhibit a wide variety of shapes, sizes, colours and arrangements that have the same basic plan. It consists of the following:
(i) Calyx: It is the outermost whorl of the flower made up of sepals. This is green, leaf-like structure. It may be polysepalous (sepals free), gamosepalous (sepals united), calyx may be regular or irregular.

(ii) Corolla: It is the second whorl of the flower inside the sepals. The petals (units of corolla) are usually brightly coloured. The insects are attracted due to the attractive colour of the petals. The corolla may be polypetalous (petals not united) or gamopetalous (petals united).

(iii) Androecium: It is the third whorl of the flower inside the petals. It represents the male reproductive whorl. Its units are stamen. In each stamen there are three parts viz:

• Anther: Knob-like bilobed structure containing the pollen grains. Each lobe contains two chambers called pollen sac.
• Connective: A strip of tissue, which connects the anther lobe is called connective.
• Filament: A slender stalk by which anther lobes are attached is called filament. If the stamen is sterile then it is called ‘staminode’.

(iv) Gynoecium: It is the female part of the flower. It is made up of ‘carpels’. A typical carpel is made up of three parts:

• Stigma: Upper part which receives pollen grains.
• Style: The stalk between stigma and ovary.
• Ovary: Basal part containing ovules. The sterile gynoecium is known as ‘pistillode’.

Question 27.
Read the following and answer the questions given below with explanation: 5×1=5
Proteins are polypeptide chains made up of amino acids. There are 22 types of amino acids joined together by peptide bond between amino and carboxylic group. There are two kinds of amino acids: Essential amino acids and Non-essential amino acids. The Primary structure of protein is the linear sequence of amino acids in a polypeptide chain. The first amino acid of sequence is called N-terminal amino acids and last amino acid of peptide chain is called C-terminal amino acids. The secondary structure proteins forms helix.

There are three types of secondary structure: a helix, p pleated and collagen helix. In tertiary structure long protein chain is folded upon itself like a hollow woollen ball to give three-dimensional view of protein. In quaternary structure, each polypeptide develops its own tertiary structure and function as subunit of protein.

(i) Amino acids, as the name suggests, have both an amino group and a carboxyl group in their structure. In addition, all naturally occurring amino acids (those which are found in proteins) are called L-amino acids. From this, can you guess from which compound can the simplest amino acid be made?
(A) Formic acid
(B) Methane
(C) Phenol
(D) filter
Answer:
(D) filter
Explanation:
Glycine is the simplest amino acid which have both an amino group of a carboxyl group in their structure a single hydrogen atom as its side chain.

(ii) Many organic substances are negatively charged e.g., acetic acid, while others are positively charged e.g., ammonium ion. An amino acid under certain conditions would have both positive and negative charges simultaneously in the same molecule. Such a form of amino acid is called:
(A) Positively charged form
(B) Negatively charged form
(C) Neutral form
(D) Zwitter ionic form
Answer:
(D) Zwitter ionic form
Explanation:
Under certain condition an amino acid may have both positive and negative charges simultaneously in the same molecule. Such a form of amino acid is known as Zwitter ionic form.

(iii) How many secondary structures are there?
(A) Two
(B) Three
(C) Four
(D) Five
Answer:
Explanation:
There are three types of secondary structure: a helix, pleated and collagen helix.

(iv) The tertiary structure of a protein contains
(A) Hydrogen bonds
(B) Peptide bonds
(C) Ionic bonds and S-linkage
(D) All the above
Answer:
(D) All the above
Explanation:
Tertiary Structure of protein is maintained by several types of bonds such as hydrogen bonds, ionic bonds, sulphide bonds and hydrophilic and hydrophobic bonds formed between are part of polypeptide and another.

(v) How many amino acids are there?
(A) 20 types.
(B) 21 types.
(C) 27 types.
(D) None of the above.
Answer:
(D) None of the above.
Explanation:
Amino acids are monomers of protein and are not of nucleic acid. Proteins are built from a set of only 22 amino