CBSE Sample Papers for Class 11 Biology Set 1 with Solutions

students must start practicing the questions from CBSE Sample Papers for Class 11 Biology with Solutions Set 1 are designed as per the revised syllabus.

CBSE Sample Papers for Class 11 Biology Set 1 with Solutions

Time Allowed : 3 hours
Maximum Marks: 70

General Instructions :

All questions are compulsory.
The question paper has four sections: Section A, Section B, Section C and Section D. There are 27 questions in the question paper.
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.
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.
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): An anti-coagulant hirudin is present in salivary glands of leech.
Reason (R): It leads to blood clotting while the leech is feeding.
(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) Q A is true but R is false.
(D) A is false but R is true.
Answer:
(C) Q A is true but R is false.
Explanation:
An anti-coagulant hirudin is present in the salivary glands of leech. It prevents the blood from clotting while the leech is feeding.

Question 2.
Assertion (A): Rheumatoid arthritis is an autoimmune disease.
Reason (R): It is an inflammation of the synovial membrane in synovial joints.
(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:
Rheumatoid arthritis is an inflammation of the synovial membrane in synovial joints. It is classified as an autoimmune disease because it is caused by the cells of the body’s immune system attacking the cells that line the joints, known as the synovial cells.

Question 3.
What would be the cardiac output of a person having 72 heartbeats per minute and a stroke volume of 50 ml?
(A) 360 ml.
(B) 3600 ml.
(C) 5000 ml.
(D) 7200 ml.
Answer:
(B) 3600 ml.
Explanation:
The cardiac performance of a person can be measured by multiplying the stroke volume and heart rate. To change the human’s cardiac output, the stroke volume, as well as the heart rate, will also be changed.
Thus, 72 × 50 = 3600 mL is a person’s cardiac output of 72 heartbeats per minute and 50 mL of stroke volume.

Question 4.
Many elements are found in living organisms either free or in the form of compounds. One of the following is
NOT found in living organisms:
(A) Silicon.
(B) Magnesium.
(C) Iron.
(D) Sodium.
Answer:
(A) Silicon.
Explanation:
The other elements are found in living organisms.

Question 5.
A common characteristic feature of plant sieve tube cells and most of the mammalian erythrocytes is:
(A) Absence of mitochondria
(B) Presence of cell wall
(C) Presence of haemoglobin
(D) Absence of nucleus
Answer:
(D) Absence of nucleus

Section – B

Question 6.
What is the difference between stele and vascular bundle?
Answer:
Difference between Stele and Vascular bundle:

Stele	Vascular bundle
(i) It is a conducting tissue or the central part of the root or stems in plants.	Vascular bundles are conducting tissues of xylem or phloem.
(ii) It comprises vascular tissue, ground tissue and pith and limiting boundaries i.e., endodermis and Pericycle.	It comprises xylem, phloem and cambium.

Question 7.
What are glycans? How are they formed?
Answer:
Complex carbohydrates or polysaccharides are called glycans. They are long chains formed by polymerisation of large number of monosaccharide monomers and are joined by glycosidic bonds with loss of water.

Question 8.
(a) What will happen if a plant is given only green light?
(b) Mention the difference between the structure of chlorophyll ‘a’ and chlorophyll ‘b’.
Answer:
(a) If a plant is given only green light, no photosynthesis will occur. Green light is not absorbed by the photosynthetic pigments as it is reflected back.
(b) Chlorophyll ‘a’ has methyl (CH₃ ) group and Chlorophyll ‘b’ has an aldehydes (CHO) group.

Question 9.
(a) What is meant by the term osmoregulation?
(b) A healthy adult human excretes (on an average) gm of urea/day.
Answer:
(a) Osmoregulation is a process that regulates the body’s salt and water concentration.
(b) 25-30 g of urea/day

Question 10.
Which portal system is present in man? Write its two advantages.
Answer:
Hepatic portal system is present in man. It has the following significance:
(i) The blood which comes from the alimentary canal contains digested food like glucose and amino acids. The excess glucose is converted into glycogen which is stored in the liver for later use. When an individual feels deficiency of food, the glycogen is converted into glucose and is transferred to the bloodstream via hepatic veins.

(ii) Harmful nitrogenous waste like ammonia is converted into urea which is later removed by kidneys. Thus, the blood is detoxified (purified) of harmful nitrogenous waste

Question 11.
List two ways by which molecules of ATP are produced in glycolysis during aerobic respiration in a cell.
Answer:
Molecules of ATP are produced in two ways in glycolysis by:

Direct transfer of phosphate from biphosphoglycerate to ADP
During formation of phosphoenol pyruvate. The phosphate radical picks up energy which helps in the production of ATP.

Question 12.
What do you understand by interphase?
Answer:

Interphase is a series of changes that occur in a newly formed cell and its nucleus before it becomes capable of division again.
It is also called inter mitosis. It is non-dividing state of the cell and its nucleus is called interphase nucleus.

Section – C

Question 13.
Describe the following:
(i) Synapsis
(ii) Bivalent
(iii) Chiasmata
Draw a diagram to illustrate your answer.
Answer:

(i) Synapsis: It is the pairing of homologous chromosomes during cell division. It occurs in Zygotene stage of Prophase I.

(ii) Bivalent: Complex formed by a pair of synapsed homologous chromosomes is called a bivalent. It is also known as a tetrad. It occurs in Zygotene stage of Prophase I.

(iii) Chiasmata: It is the point of crossing of two non-sister chromatids. It is X-shaped point of interchange of chromosomes. It is formed during diplotene stage of Prophase I.

Question 14.
What is the role played by Renin-Angiotensin in the regulation of kidney function?
Answer:
A fall in glomerular blood flow/glomerular blood pressure/GFR activates the JG cells to release renin. Renin converts angiotensinogen in blood to angiotensin I and further to angiotensin II (avasoconstrictor).

Angiotensinogen renin → Angiotensin I → Angiotensin II

Angiotensin II is a powerful vasoconstrictor that increases the glomerular blood pressure and thereby GFR. Angiotensin II also stimulates the adrenal cortex of the adrenal gland to produce aldosterone. Angiotensin II increases glomerular blood pressure and thereby GFR. It also activates adrenal cortex to release Aldosterone. Aldosterone increases the rate of absorption of sodium ions and water from the distal convoluted tubule and the collecting duct. This also leads to an increase in blood pressure and glomerular filtration rate. This mechanism, known as renin-angiotensin mechanism, ultimately leads to an increased blood pressure.

Question 15.
What is the importance of morphology?
Answer:
Importance of Morphology:

Knowledge of morphology is essential for the recognition or identification of plants.
Certain important criteria for classification of plants are obtained from morphology.
It gives information about the range of variations found in a species.
Knowledge of morphology is required for studying various aspects of plant life like genetics, ecology, anatomy, etc. (Any three)

Question 16.
Write the functions of the following
(i) Smooth ER
(ii) Golgi Apparatus
(iii) Centrioles
Answer:
(i) Smooth ER: SER is involved in steroid synthesis, intercellular transport and detoxification.

(ii) Golgi apparatus: Secretion is the major function of Golgi apparatus. All types of substances that are secreted and excreted are packed in vesicles by Golgi bodies for passage to the outside. It is the secretory organelle of the cell. Golgi apparatus is the important site of formation of glycoproteins and glycolipids.

(iii) Centriole: Centriole helps in the formation of spindle fibres during cell division. Centriole also produces basal
bodies that form cilia and flagella. Basal bodies direct the formation of cilia and flagella.

Question 17.
Write three important features of cartilaginous fish and bony fish. Also give one examples of each of these.
OR
Describe the structure of viruses.
Answer:
Special characters present in cartilaginous and bony fish:

Cartilaginous Fish	Bony Fish
(i) Skin is covered by small placoid scales.	Skin is covered with large cycloid or ganoid or ctenoid scales.
(ii) Endoskeleton is cartilaginous.	Endoskeleton is partly or whole bony.
(iii) Tail fin is heterocercal.	Tail fin is homocercal.
Example: Sharks, Rays.	Example: Labeo Rohita, Catla Catla.

Viruses means venom or poisonous fluid. These were discovered by Ivanovsky. Viruses are composed of nucleoproteins. Structurally a virus consists of following major parts:
(i) Nucleoid: It is the core of nucleic acid and is infective part of the virus. It is the genetic material in the form of either DNA or RNA. The nucleic acid of viruses can be of four types:
(a) Double-stranded DNA
(b) Single-stranded DNA
(c) Single-stranded RNA
(d) Double-stranded RNA.

(ii) Capsid: The nucleoid is covered by a protein coat called capsid. It is made up of specifically arranged sub-units called capsomeres.

(iii) Envelope: Some animal viruses like HIV have loose covering over the capsid called envelope. It is made up of proteins, lipids and carbohydrates. The proteins of the capsid or envelope act as antigens.

(iv) Enzymes: A few proteins in some viruses are enzymatic in functions. e.g., lysozyme in bacteriophage. Viruses causes serious disease in humans, animals and plants like mumps, small pox, herpes, influenza and AIDS, etc.

Question 18.
Name the T3 and T4 components of the thyroid hormone. Explain their specific functions.
Answer:
T3-Tri-iodo-thyronine and T4-tetraiodothyronine or thyroxine.
Thyroid hormones perform the following functions:

They regulate the metabolic rates of the body and thus maintains basal metabolic rate.
Thyroid hormones control the metabolism of carbohydrates, proteins and fats.
They promote the growth of the body tissues.

Question 19.
What are the modifications that are observed in bird that help them fly?
OR
What is the basis of classification of algae?
Answer:

Birds have feathers which help them to fly.
Forelimbs are modified into wings for flight.
The avian flight muscles are used for flying.
The long bones are hollow and contain air cavities to reduce weight.
The bones are light.
Feathers decrease water loss from the body.
High metabolic rate to lift body from the ground.
Urinary bladder is absent. Excreta is passed out at once these features help in reducing the weight of the body.

OR
Algae are classified on the basis of:

Type of pigments they possess.
Chemical nature of reserved food material.
Kinds, number and points of insertion of motile cells and
The presence or absence of organised nucleus in the cell.

Question 20.
In mammals, the lungs replace the skin very effectively as respiratory organ. Explain giving three reasons.
Answer:

Lungs provide very large surface area for the exchange of gases. Total alveolar surface area is nearly 100 m² whereas the total surface area of skin is around 1.6 m² only.
Alveoli are lined by a thin highly permeable membranous wall. These are surrounded by many blood capillaries.
Endothelium of blood capillaries and membranous walls of alveoli are highly permeable to respiratory gases.

Question 21.
Mention two similarities between

Aves and mammals
A frog and crocodile
A turtle and pila

Answer:

Similarities between Aves and Mammals: They both have a four-chambered heart and are warm blooded animals.
Similarities between frog and crocodile: They both are poikilothermous (cold-blooded animals) and are oviparous.
Similarities between turtle and Pila: Both are aquatic animals. Their body is covered with dry and cornified skin. (In turtle, the epidermal covering is known as scales while in case of Pila, it is known as calcareous shell).

Question 22.
Does it make any difference to have the haemoglobin in the corpuscles rather than in plasma? Explain.
Answer:
There is great difference in respects of efficiency of carrying the oxygen from respiratory organs to the body tissue
as follows:

Haemoglobin in corpuscles	Haemoglobin in plasma
As RBC are small, rounded and in more in quantity, so haemoglobin is exposed with large, combined surface area to absorb O₂.	It is the study of diversity of organisms and all their comparative and evolutionary relationships.
When RBC pass through the small capillaries of respiratory organs, one by one, they have ample time and surface, to absorb oxygen.	The haemoglobin dissolved in plasma has lesser time as it passes quickly, (being liquid) through the wall of capillaries.

Question 23.
Describe the fluid mosaic model of plasma membrane with the help of a labelled diagram.
(A) indole compounds.
(B) adenine derivatives
Answer:
Fluid mosaic model:

The fluid mosaic model was proposed by Singer and Nicolson.
According to this model, there is a central lipid bilayer of phospholipids with their polar head group towards the outside and the non-polar tails pointing inwards.
Some proteins which are embedded in the lipid layer are called integral or intrinsic proteins and they cannot be separated from the membrane.
There are large globular integral proteins which project beyond the lipid layer on both the sides are believed to have channels through which water-soluble materials can pass across.
Superficially attached proteins are called extrinsic or peripheral proteins and can be easily removed.
Some membrane lipids and integral proteins remains bound to oligosaccharides which project into the extracellular fluid and influence the manner in which cells interact with one another.

Question 24.
Define differentiation, development, dedifferentiation, re-differentiation, determinate growth and meristem.
Answer:

Differentiation: Differentiation is a permanent localised qualitative change in size, biochemistry, structure and function of cells, tissues or organs.
Development: It is the sequence of events that occurs in the life history of a cell, organ or organism which includes growth, differentiation, maturation, and senescence.
Dedifferentiation: The sum of events that bestow the regaining capacity in differentiated cells to divide once again are termed as dedifferentiation.
Re-differentiation: The product of dedifferentiated cells or tissues which lose the ability to divide is called re-differentiated cells or tissues and this event is called as re-differentiation.
Determinate growth: It refers to limited growth. It occurs in certain regions of a plant.
Meristem: The meristem refers to the cells that remain dividing. It is located at root and shoot tips.

Section – D

Question 25.
Schematically represent the steps of glycolysis. 5×1=5
OR
Read the following to answer any four questions from (i) to (v) given below: Give explanation of your answer: The current and projected changes in abiotic stresses such as heat, cold, drought and salinity adversely affect the plant growth that ultimately limits productivity and is the leading cause of crop losses worldwide. During stress conditions, plants reduce the growth and development process, which ultimately affects the yield. In stress conditions, plants develop various stress mechanisms to face the magnitude of stress challenges.

Therefore, many strategies have been used to produce abiotic stress tolerance crop plants, among them, Abscisic acid (ABA) phytohormone engineering could be one of the methods of choice. ABA regulates various physiological processes ranging from stomatal opening to protein storage and provides adaptation to many stresses like drought, salt, and cold stresses. ABA acts as the signalling mediator for regulating the adaptive response of plants to different environmental stress conditions.
Answer:

OR
(i) According to the chemical composition, ABA is:
(A) adenine derivatives
(B) indole compounds.
(C) derivatives of carotenoids
(D) terpenes
Answer:
(C) derivatives of carotenoids

(ii) Abscisic acid treatment results in:
(A) root elongation
(B) abscission of flowers and fruits
(C) stem elongations
(D) leaf expansion
Answer:
(B) abscission of flowers and fruits

(iii) The role of ABA is antagonistic to:
(A) Ethylene.
(B) Gibberellic acid
(C) Cytokinin
(D) IAA
Answer:
(B) Gibberellic acid

(iv) Choose the correct option:
(A) ABA causes stomatal opening.
(B) ABA causes stomatal opening and Cytokinin cause stomatal closing.
(C) Cytokinin cause stomatal closing.
(D) ABA causes stomatal closing and Cytokinin cause stomatal opening.
Answer:
(D) ABA causes stomatal closing and Cytokinin cause stomatal opening.

(v) Direction: In the following question, the Assertions (A) and Reason (R) have been put forward. Read both the statements and choose the correct option from the following:
Assertion (A): Abscisic acid stimulates the senescence of leaves.
Reason (R): During desiccation and other stresses, the concentration of abscisic acid increases in the leaves of the plants.
(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:
Abscisic acid stimulates senescence of leaves by destroying chlorophyll and inhibiting of protein and RNA synthesis. During drought and other stress, the concentration of Abscisic acid increases in the leaves of the plants which causes closure of stomata and hence prevents transpiration through the leaves.

Question 26.
(a) Differentiate between hypogynous and epigynous flowers. Give one example of each. 2+1+2
(b) What is mother axis?
(c) What do you understand by staminode and pistillode? Differentiate between staminate and pistillate flower.
OR
What do you understand by aestivation? How many types of aestivation are found?
Answer:
(a) Difference between hypogynous and epigynous flowers.

Hypogynous flowers	Epigynous flowers
(i) The ovary or gynoecium develops at the top while other floral organs are inferior.	The ovary or gynoecium develops below the level of other floral organs.
(ii) The ovary is said to be superior.	The ovary is said to be inferior.
Example: Mustard, china rose, brinjal, etc.	Example: Apple, sunflower, cucumber, guava, etc.

(b) A small circle drawn above the floral diagram represents the mother axis. Position of all the floral parts are drawn in relation to mother axis.
(c) (i) Staminode: In Verbascum and Salvia, some stamens are without pollen grains and are sterile. They are known as staminode.
(ii) Pistillode: A sterile pistil is called pistillode.

Differences between staminate flower and pistillate flower:

Staminate flower	Pistillate flower
In dioecious (unisexual) flowering plants, the male flower is called staminate.	The ovary or gynoecium develops below the level of other floral organs.

Aestivation: The arrangement of sepals or petals with respect to one another in floral bud is called ‘aestivation’.

Types of aestivation:

Valvate: The sepals or petals are arranged in a whorl which just touch one another at the margin. They do not overlap. e.g., Acacia, Calotropis.
Twisted: In this type of aestivation, one margin of a sepal or petal overlaps the next sepal or petal, and next margin is overlapped by the proceeding one, resulting in a twisted appearance. Overlapping is always in one direction. for e.g., China rose (petals), Cotton and lady’s finger.
Imbricate: In this type of aestivation, the margins of sepals or petals overlap one another but not in any definite direction. e.g., Cassia and gulmohur.
Vexillary: In this type of aestivation, the posterior petal is the largest and covers almost

Question 27.
Read the following to answer any four questions from (i) to (v) given below: 5×1=5
The gametophyte is a dominant phase in the life cycle of a bryophyte. It is more conspicuous, long-living, independent, green and freely branched whereas, the sporophytic phase is short-lived and dependent upon the gametophyte. The main plant body is haploid and bears sex organs i.e., antheridium and archegonium.

Antheridium produces a large number of flagellated male gametes called antherozoids and archegonium is flask-shaped with tubular neck and swollen venter. The gametophytic plant body of bryophytes is thalloid in liverworts whereas foliose in mosses. In liverworts, the thallus is differentiated into a dorsal photosynthetic and ventral storage region. In mosses, the gametophyte has two growth stages , protonema stage and leafy stage or gametophore.

(i) Protonema is …………
(A) Haploid and in mosses.
(B) Diploid and in liverworts.
(C) Haploid and in pteridophytes.
(D) Haploid and in pteridophytes.
Answer:
(A) Haploid and in mosses.
Explanation: Protonema is a juvenile filamentous stage of moss gametophyte.

(ii) 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.
Explanation:
Bryophytes are amphibians of plant kingdom. They grow in soil but require water for sexual reproduction. Their sperms require water to swim into the egg, also named as caecilians.

(iii) In a moss, sporophyte:
(A) manufactures food for itself as well as for gametophyte.
(B) is partially parasitic on gametophyte.
(C) produce gametes that give rise to gametophyte.
(D) arises from a spore produced from the gametophyte.
Answer:
(B) is partially parasitic on gametophyte.
Explanation:
Moss sporophyte remain attached on gametophyte and absorb nutrient from it. It becomes green in some region and thus, becomes photosynthetic and prepares it own food, thus it is partially parasitic on gametophytic.

(iv) Plants which produce spores and embryo but lack vascular tissue and seeds are:
(A) Bryophytes
(B) Pteridophytes
(C) Gymnosperm
(D) Algae
Answer:
(A) Bryophytes
Explanation:
Bryophytes are non-vascular embryophytes.

(v) Direction: Assertions (A) and Reasons (R) have been put forward. Read both the statements and choose the correct option from the following:
Assertion (A): Moss protonema resemble green alga.
Reason (R): It develops unicellular sex-organs.
(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:
(C) A is true but R is false.
Explanation:
Moss protonema unlike green alga bears oblique septa and produces, not sex organs, but gametophores.