Madhyamik Class 10 Life Science Solved Paper 2022

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Madhyamik Class 10 Life Science Solved Paper 2022

LIFE SCIENCE

Time: 3 Hours and 15 Minutes

(First 15 Minutes for reading the question paper only, 3 Hours for writing) 

Full Marks: For Regular Candidates – 90

For External Candidates – 100

Regular candidates will answer questions from Groups A, B, C and D. External candidates will answer questions from Group E.

(Special Instructions for visually handicapped candidates)

Answer Question 4.1(A) instead of Question 4.1 in Group D. Instruction on how many questions from a group must be attempted is provided at the beginning of the group.

Group ‘A’
(All questions are compulsory)

1. Choose the correct answer for each question and write it with its respective-serial number: [1 × 15=15]

Question 1.1

Select the correct pair —

  1. Sclera—Absorbs excess light within the eyeball
  2. Choroid—Provides definite shape of the eyeball
  3. Lens—Causes refraction of light and accomplishes accomodation
  4. Retina—Holds the lens with the help of the suspensory ligaments

Answer

Lens—Causes refraction of light and accomplishes accommodation

Question 1.2

Identify which of the following statements is not true regarding Adrenaline —

  1. Increases the rate of heartbeat
  2. Helps in the production of spermatozoa during adolescence
  3. Increases cardiac output
  4. Increases systolic blood pressure

Answer

Helps in the production of spermatozoa during adolescence

Question 1.3

Select which of the following is the feature of tropic movement —

  1. Induced movement of curvature of particular parts of plant controlled by the direction of the stimulus
  2. It is one type of turgor movement
  3. Induced movement of curvature of particular parts of plant controlled by the intensity of the stimulus
  4. Does not occur under the influence of Auxin

Answer

induced movement of curvature of particular parts of the plant controlled by the direction of the stimulus.

Question 1.3

Match the words of Column-A with that of Column-B and select which of the following options is correct —

Column-A Column-B
A. CSF

B. Meninges

C. Neuroglia

 i. Protects Central Nervous System from mechanical injury

ii. Helps in the formation of the myelin sheath

iii. Acts as a shock absorber

 

  1. A-(ii) B-(iii) C-(i)
  2. A-(iii) B-(i) C-(ii)
  3. A-(i) B-(ii) C-(iii)
  4. A-(i) B-(iii) C-(ii)

Answer

A-(i) B-(iii) C-(ii)

Question 1.5

Decide which of the following sequence is correct —

  1. Receptor → Effector → Sensory Nerve → Motor Nerve → Nerve Centre
  2. Receptor → Nerve Centre → Motor Nerve → Sensory Nerve → Effector
  3. Receptor → Sensory Nerve → Nerve Centre → Motor Nerve → Effector
  4. Receptor → Motor Nerve → Effector → Sensory Nerve → Nerve Centre

Answer

Receptor → Sensory Nerve → Nerve Centre → Motor Nerve → Effector

Question 1.6

Select the correct pair —

  1. Telophase — Movement of daughter chromosomes towards poles
  2. Telophase — Disappearance of Nuclear Membrane and Nucleolus
  3. Telophase — Formation of spindle fibre
  4. Telophase — Reappearance of Nuclear Membrane and Nucleolus

Answer

Telophase — Reappearance of Nuclear Membrane and Nucleolus

Question 1.7

The name of the terminal parts of the Chromosome is —

  1. Centromere
  2. Telomere
  3. Nucleolar Organizer
  4. Satellite

Answer

Telomere

Question 1.8

Identify which of the following statements is not true regarding cross-pollination —

  1. Requires agent
  2. Origin of new hereditary features
  3. Maintains the purity of species
  4. The rate of germination of seeds is higher

Answer

Maintains the purity of species

Question 1.8

Consider the differences between asexual and sexual reproduction and select which of the options is/are correct —

Asexual Reproduction Sexual Reproduction
I. Requires two parental organisms of opposite sex belonging to the same species.

II. This type of reproduction is completed through cell division or through the production of spores.

III. Depends on amitosis, mitosis and meiosis.

IV. Variations are found in offsprings.

 Offsprings can be formed from a single parental organism.

This type of reproduction is completed through the production of gametes and their union.

Depends on meiosis.

The offsprings become identical to their parents.

 

  1. I, IV
  2. II, III
  3. III, IV
  4. I, II

Answer

I, II

Question 1.10

Select the correct pair in the case of humans:

  1. Normal pattern of chromosome of ovum — 22A + XX
  2. Normal pattern of chromosome of ovum — 22A + Y
  3. Normal pattern of chromosome of ovum — 22A + X
  4. Normal pattern of chromosome of ovum — 22A + XY

Answer

Normal pattern of chromosome of ovum — 22A + X

Question 1.11

Determine which of the following genotypes is homozygous for both the loci

  1. BbRr
  2. BBRr
  3. BbRR
  4. bbrr

Answer

BBRR

Question 1.12

Identify the genotype of guineapig having white coat colour and rough nair —

  1. bbRR, bbrr
  2. BBRR, bbrr
  3. bbRR, bbRr
  4. BbRr, BbRR

Answer

bbRR, bbRr

Question 1.13

Decide which of the following two were selected by Mendel as dominant traits —

  1. Length of stem – Long, Shape of seed — Round
  2. Position of flower — Terminal, Colour of flower — White
  3. Colour of the cotyledon — Green, Shape of seed — Wrinkled
  4. Length of stem – Dwarf, Shape of seed — Wrinkled

Answer

Length of stem – Long and shape of seed – Round

Question 1.14

Determine the nature of the pea plant germinated from the seed produced as a result of pollination between a hybrid tall (Tt) and a pure dwarf (tt) pea plant

  1. 100% Tall
  2. 50% Tall, 50% Dwarf
  3. 100% Dwarf
  4. 75% Tall, 25% Dwarf

Answer

50% Tall, 50% Dwarf

Question 1.15

Decide which of the following diseases can be prevented by taking suggestions from pre-marital genetic counselling –

  1. Goitre
  2. Malaria
  3. Thalassaemia
  4. Tuberculosis

Answer

thalassemia

Group — ‘B’

Answer 21 questions out of 26 questions given below as instructed. [1×21=21]

Question 2.1 – 2.6

Fill in the blanks (any five) [1 × 5=5]

  1. ____ hormone is found in very high amounts in the ripe seeds of plants.
  2. Reflex action is fast, spontaneous and ____.
  3. In ____ cell division spindle fibres are not formed.
  4. ____ is an entomophilous flower.
  5. The gene having the power of the rolling tongue is ____.
  6. As the gene responsible for haemophilia is recessive, so the symptoms of this disease is only manifested in ____ condition.

Answer

  1. Abscisic acid is found in very high amounts in the ripe seeds of plants.
  2. Reflex action is fast, spontaneous and unlearned.
  3. In meiosis cell division spindle fibres are not formed.
  4. Lotus is an entomophilous flower.
  5. The gene having the power of the rolling tongue is dominant.
  6. As the gene responsible for haemophilia is recessive, so the symptoms of this disease is only manifested in homozygous recessive condition.

Question 2.2 – 2.6

Decide whether the following statements are true or false (any five) :

  1. The focal length of lens increases in case of seeing distant objects.
  2. Each nucleoside contains a nitrogenous base and phosphoric acid.
  3. There is no role of female in determining sex of human.
  4. If any pea plant contains either TT or tt trait, then the pea plant becomes heterozygous with respect to such alleles.
  5. As the flowers of pea plant are unisexual, so self-pollination and if needed, cross pollination can be performed.
  6. The daughter cells are changed and modified in different ways during cell differentiation phase to form tissue, organ and system.

Answer

  1. False; The focal length of the lens decreases when you look at distant objects.
  2. True
  3. False; The female does have a role in determining the sex of the human. The sex of the human is determined by the X and Y chromosomes. The female has two X chromosomes, while the male has one X and one Y chromosome. If the sperm that fertilizes the egg has an X chromosome, the baby will be a girl. If the sperm has a Y chromosome, the baby will be a boy.
  4. False; If a pea plant contains either TT or tt trait, then the pea plant is homozygous with respect to such alleles.
  5. True
  6. True

Question 2.3

Match the words in column-A with the most appropriate words in column B and re-write the correct pair mentioning the serial no. of both columns (any five):-  [1 × 5=5]       

Column-A Column-B
1. Diabetes insipidus

2. Schwann cell

3. Meiosis

4. Senescence phase

5. Genetic disease

6. The second law of Mendel

 a) Law of Independent Assortment

b) Brittleness of bone

c) Exists between neurolemma and myelin sheath of axon

d) Hyposecretion of ADH

e) Spore mother cell and germ mother cell

f) Colour blindness

g) Law of Segregation

Answer

1 – (d); 2 – (c); 3 – (e); 4 – (b); 5 – (f); 6 – (g)

Question 2.4

Answer in a single word or in a single sentence (any six) [1 × 6=6]

  1. Choose the odd one and write it :
    Olfactory nerve, Vagus nerve, Optic nerve, Auditory nerve
  2. What is the fate of hormones in the animal body after their function is over?
  3. A pair of related terms is given below. On the basis of the relationship in the
    first pair write the suitable word in the gap of the second pair.
    Purine: Adenine : : Pyrimidine : ____
  4. What happens if the functions of checkpoints in the cell cycle get hampered?
  5. What is hybridization?
  6. What is a dominant trait?
  7. Among the following four terms, one includes the other three. Find it out and write it :
    Increase in Basal Metabolic Rate, Thyroxine, Gradual maturation of Red Blood Corpuscle, Exopthalmic Goitre
  8. In which phase of Interphase are the proteins essential for the formation of spindle fibres is synthesized?

Answer

  1. Auditory nerve (The other options are all cranial nerves related to senses)
  2. Degradation or excretion
  3. Cytosine
  4. Uncontrolled cell division or abnormal cell growth
  5. The process of combining two different species or varieties to create a hybrid offspring.
  6. A trait is expressed when an organism has one copy of the corresponding gene, masking the effect of the recessive allele if present.
  7. Exophthalmic Goitre (Thyroxine is involved in the increased basal metabolic rate and gradual maturation of red blood corpuscles in exophthalmic goitre)
  8. S phase (Synthesis phase)

Group – ‘C’

3. Answer any 12 questions in 2-3 sentences out of 17 questions given below: [2×12=24]

Question 3.1

Prepare a list of hormones which control the following functions —

  • Causes an increase in the length of bones through mineralisation of the matrix of cartilage located at the terminal parts of long bones.
  • Transforms ruptured follicle into a temporary endocrine gland namely Corpus Luteum and provides necessary stimulation for the secretion of Progestrone hormone from that gland.
  • Inhibits the production of glucose in liver from protein and lipids.
  • Causes contraction of uterine muscles during parturition.

Answer

  • Growth hormone causes an increase in the length of bones through the mineralisation of the matrix of cartilage located at the terminal parts of long bones.
  • Luteinizing hormone (LH) transforms the ruptured follicle into a temporary endocrine gland namely Corpus Luteum and provides necessary stimulation for the secretion of Progesterone hormone from that gland.
  • Insulin inhibits the production of glucose in the liver from protein and lipids.
  • Oxytocin causes the contraction of uterine muscles during parturition.

Question 3.2

Explain the causes of Myopia and Hyperopia.

Answer

  • Myopia (nearsightedness) is caused by the eyeball being too long from front to back. This causes light to focus in front of the retina instead of on it, making distant objects appear blurry.
  • Hyperopia (farsightedness) is caused by the eyeball being too short from front to back. This causes light to focus behind the retina instead of on it, making close objects appear blurry.

Question 3.3

Explain what phenomena happen when the following muscles contract :

  • Flexor muscle
  • Extensor muscle
  • Abductor’s muscle
  • Rotator muscle

Answer

  • Flexor muscle: A flexor muscle contracts to bend a joint. For example, when you bend your elbow, the biceps muscle contracts, which is a flexor muscle.
  • Extensor muscle: An extensor muscle contracts to straighten a joint. For example, when you straighten your elbow, the triceps muscle contracts, which is an extensor muscle.
  • Abductor muscle: An abductor muscle contracts to move a limb away from the body’s midline. For example, when you move your arm out to the side, the deltoid muscle contracts, which is an abductor muscle.
  • Rotator muscle: A rotator muscle contracts to rotate a limb. For example, when you rotate your arm clockwise, the rotator cuff muscles contract, which are rotator muscles.

Question 3.4

Prepare a list of functions controlled by Auxin related to the growth of plants.

Answer

Function Description
Apical dominance Auxin inhibits the growth of lateral buds, which allows the apical bud to grow taller.
Cell elongation Auxin promotes cell elongation, which is responsible for the growth of stems and roots.
Tropism Auxin helps plants to grow in a certain direction, such as towards sunlight (phototropism) or towards gravity (gravitropism).
Formation of adventitious roots Auxin can stimulate the formation of adventitious roots, which are roots that grow from non-root tissues.
Xylem differentiation Auxin helps to differentiate xylem cells, which are the cells that transport water and nutrients up the stem of a plant.

Question 3.5

Distinguish between the mitosis of plant cells with the mitosis of animal cells on the basis of the following features —

  • Formation of spindle fibres
  • Process of cytokinesis

Answer

Formation of spindle fibres

  • Plant cells: Spindle fibres are formed by the centrioles, which are located in the centrosome.
  • Animal cells: Spindle fibres are formed by the centrosomes, but the centrioles are not always present. If the centrioles are not present, the spindle fibres are formed by the microtubules.

Process of cytokinesis

  • Plant cells: Cytokinesis in plant cells is called cell plate formation. A cell plate is a new cell wall that is formed between the two daughter cells.
  • Animal cells: Cytokinesis in animal cells is called cleavage furrow formation. A cleavage furrow is a groove that forms in the cell membrane, and it eventually pinches the cell in two.

Question 3.6

Explain how Bryophyllum undergoes vegetative propagation with the help of an adventitious bud.

Answer

Bryophyllum undergoes vegetative propagation with the help of an adventitious bud:

  • Adventitious buds arise along the margins of the leaves of Bryophyllum.
  • These buds grow and develop into small plantlets.
  • The plantlets eventually fall off the leaf and roots in the soil.
  • The plantlets then grow into new mature plants.

Question 3.7

Tabulate which changes occur in a chromosome during the Anaphase of Karyokinesis.

Answer

Change Description
Centromere splits The centromere, which is the region of the chromosome that holds the two sister chromatids together, splits.
Sister chromatids separate The sister chromatids, which are two identical copies of the chromosome, are pulled apart by the spindle fibres.
Chromosomes move to opposite poles The chromosomes are pulled towards the opposite poles of the cell by the spindle fibres.
Daughter chromosomes form The chromosomes arrive at the opposite poles of the cell, and each pole now has a complete set of chromosomes.

Question 3.8

Describe how Yeast completes the process of budding.

Answer

Yeast completes the process of budding by initiating the formation of a small bud on its surface, which grows in size and eventually separates from the parent cell. During budding, the nucleus of the parent cell replicates and migrates into the bud, ensuring that the genetic material is transferred to the new offspring. Once the bud reaches a sufficient size, it detaches, becoming an independent yeast cell capable of further growth and reproduction.

Question 3.9

Prepare a list of changes which occur during the adolescence phase of human development.

Answer

  • Growth spurt: Rapid growth in height and weight.
  • Sexual maturation: Development of secondary sex characteristics, such as breasts, pubic hair, and facial hair.
  • Acne: Breakouts of pimples on the face and body.
  • Body odour: Increased production of sweat and body odour.

Question 3.10

Explain the following two significance of meiotic cell division —

  • Maintains the constant number of chromosomes in a species
  • Origin of variation in an organism

Answer

  1. Meiotic cell division maintains the constant number of chromosomes in a species by halving the chromosome number, ensuring that offspring receive the correct amount of genetic material.
  2. Meiotic cell division is significant for the origin of variation in an organism as it allows for genetic recombination through processes like crossing over and independent assortment, leading to the creation of genetically diverse offspring with unique combinations of traits.

Question 3.11

State Mendel’s second law of heredity.

Answer

Mendel’s second law of heredity, also known as the Law of Independent Assortment, states that alleles for different traits segregate independently during the formation of gametes.

Question 3.12

Prove the authenticity of the statement — “The phenotypic and genotypic ratio remain identical in case of Incomplete Dominance”.

Answer

In the case of incomplete dominance, the phenotypic and genotypic ratios are not identical. The phenotypic ratio may differ from the genotypic ratio due to the expression of intermediate traits in heterozygous individuals, resulting in a different observable phenotype ratio compared to the underlying genotypes.

Question 3.13

Write two causes behind Mendel’s success in conducting experiments on heredity.

Answer

Two causes behind Mendel’s success in conducting experiments on heredity were:

  1. Mendel’s careful selection of pea plants as experimental organisms had distinct and easily recognizable traits that could be observed and measured accurately.
  2. Mendel’s meticulous record-keeping and quantitative analysis of the data collected from his experiments, allowed him to discern clear patterns and formulate the principles of inheritance.

Question 3.14

“Dispersal of animals is one of the driving forces of locomotion” – Judge the statement with the help of proper examples.

Answer

Dispersal of animals, which refers to their movement from one location to another, can indeed be a driving force of locomotion. For example, migratory birds travel long distances to find suitable breeding grounds or food sources. Similarly, many species of fish undertake extensive migrations to spawn in specific areas. These dispersal movements are essential for survival, reproduction, and accessing resources, making them a significant driving force behind animal locomotion.

Question 3.15

Show the chemical constituents of chromosomes with the help of a table.

Answer

Chemical Constituents Description
DNA (Deoxyribonucleic Acid) Carries genetic information in the form of nucleotide sequences
Histones Proteins that help in DNA packaging and organization
Non-histone Proteins Involved in various functions like gene regulation and replication
RNA (Ribonucleic Acid) Plays a role in gene expression and protein synthesis
Nucleotides Basic building blocks of DNA and RNA

Question 3.16

Compare DNA and RNA on the basis of the following features —

  • Nature of carbohydrate
  • Nature of pyrimidine base

Answer

Features DNA RNA
Nature of carbohydrate Deoxyribose Ribose
Nature of pyrimidine base Cytosine (C), Thymine (T) Cytosine (C), Uracil (U), Adenine (A)

Question 3.17

“Some phenotypes may have multiple genotypes and some other phenotypes may have a single genotype” —Justify the statement from the results derived from the dihybrid experiment in the case of the pea plant.

Answer

The statement “Some phenotypes may have multiple genotypes and some other phenotypes may have a single genotype” is justified by the results derived from the dihybrid experiment in the case of the pea plant. For example, the phenotype of round can be either DD or dd, while the phenotype of yellow can only be YY. This is because the round phenotype is dominant over the wrinkled phenotype, and the yellow phenotype is dominant over the green phenotype.

Group – ‘D’

(Long Answer Type Questions)

4. Write the 6 questions or their alternatives given below. Sightless candidates have to answer question No. 4.1(A) instead of question no. 4.1 The marks allotted for each question is 5 (the division of marks is either 3+2, 2+3 or 5) :

Question 4.1

Draw a scientific diagram of a neurone and label the following parts :

  1. Axon
  2. Node of Ranvier
  3. Dendron
  4. Schwann Cell

Answer

Neurone

OR

Draw a scientific diagram of the morphological structure of a eukaryotic chromosome and label the following parts

  1. Chromatid
  2. Telomere
  3. Centromere
  4. Nucleolar Organizer

Answer

morphological structure of a eukaryotic chromosome

(FOR SIGHTLESS CANDIDATES ONLY)

4.1 (A) Write the functions of each of the following parts of a neurone :

  1. Dendron
  2. Axon
  3. Myelin Sheath
  4. Schwann Cell
  5. Node of Ranvier

Answer

Part of neuron Function
Dendrites Receive signals from other neurons.
Axon Transmits signals to other neurons.
Myelin sheath Insulates the axon and speeds up the signal transmission.
Schwann cell Produces the myelin sheath.
Node of Ranvier Gaps in the myelin sheath that allow signals to jump across.

OR

Write the functions of the following structural parts of a eukaryotic chromosome:

  1. Centromere
  2. Nucleolar Organizer
  3. Chromatid
  4. Telomere
  5. Kinetochore

Answer

Part of chromosome Function
Centromere Attaches the two chromatids of a chromosome.
Nucleolar organizer Contains the genes for rRNA.
Chromatid One of the two identical copies of a chromosome.
Telomere Protects the end of a chromosome from damage.
Kinetochore Attaches the chromosome to the spindle fibers during mitosis and meiosis.

Question 4.2

Compare the antagonistic functions of the following three pairs of hormones in the human body:

  • Insulin and Glucagon
  • Estrogen and Progesterone
  • FSH and LH

Explain the relationship between the hindbrain and the function of control of the breathing mechanism.

Answer

Hormone pair Function
Insulin and glucagon Insulin lowers blood sugar levels, while glucagon raises blood sugar levels.
Estrogen and progesterone Estrogen promotes female sexual development, while progesterone prepares the uterus for pregnancy.
FSH and LH FSH stimulates the growth of eggs in the ovaries, while LH triggers ovulation.

The hindbrain is responsible for controlling the breathing mechanism. The medulla oblongata, which is part of the hindbrain, contains the respiratory centre. The respiratory centre is responsible for sending signals to the muscles that control breathing. These signals control the rate and depth of breathing.

OR

The following physiological functions of a person wounded in an accident are found hampered. Write the name of the parts of the brain attached to those functions:

  • Speech
  • Hunger, thirst and sleep
  • Posture and the equilibrium of the body
  • Movement of tongue and swallowing of food

Explain the mechanism of feedback control of the function of hormones with the help of a suitable example.

Answer

The parts of the brain that are associated with the following physiological functions:

  • Speech: Broca’s area in the frontal lobe is responsible for speech production.
  • Hunger, thirst, and sleep: The hypothalamus in the diencephalon is responsible for these functions.
  • Posture and the equilibrium of the body: The cerebellum in the hindbrain is responsible for these functions.
  • Movement of tongue and swallowing of food: The medulla oblongata in the hindbrain is responsible for these functions.

Feedback control is a mechanism that helps to keep hormones within a narrow range. This is important because hormones play a vital role in many bodily functions, and too much or too little of a hormone can have negative consequences.

One example of feedback control is the regulation of blood sugar levels by insulin. When blood sugar levels rise, the pancreas releases insulin. Insulin then binds to cells and signals them to take in glucose from the blood. This lowers blood sugar levels. When blood sugar levels fall, the pancreas stops releasing insulin.

Question 4.3

Prepare a list of role of artificial plant hormones in agriculture and horticulture. What are the influences of Insulin hormone on the absorption and metabolism of glucose in the human body?

Answer

  1. Auxin: Promotes cell elongation and root development.
  2. Cytokinin: Promotes cell division and bud formation.
  3. Gibberellin: Promotes stem elongation and seed germination.
  4. Abscisic acid: Promotes seed dormancy and leaf abscission.
  5. Ethylene: Promotes fruit ripening and leaf senescence.

OR

Write three differences between binocular vision with that of monocular vision on the following three aspects :

  • Formation of image
  • Field of vision
  • Depth

Write differences between inborn and acquired reflex actions on any two of the following aspects —

  • Nature
  • Condition
  • Prior experience
  • Neural pathway

Answer

Aspect Binocular vision Monocular vision
Formation of image Two images are formed on the retinas of the eyes, which are then fused in the brain to create a single three-dimensional image. Only one image is formed on the retina of the eye.
Field of vision The field of vision is wider than with monocular vision. This is because each eye can see a different part of the environment. The field of vision is narrower than with binocular vision. This is because only one eye can see at a time.
Depth perception Depth perception is better with binocular vision than with monocular vision. This is because the brain can use the difference in the images from the two eyes to determine the distance of objects. Depth perception is possible with monocular vision, but it is not as good as with binocular vision. This is because the brain can only use cues such as perspective and occlusion to determine the distance of objects.

The differences between inborn and acquired reflex actions on the following two aspects:

Aspect Inborn reflex Acquired reflex
Nature Present from birth Learned over time
Condition No prior experience required Requires prior experience
Neural pathway Simple reflex arc Complex reflex arc

Question 4.4

Show the alternation of generation in fern with the help of a word diagram.

Answer

Alternation of generation

OR

Show the process of sexual reproduction in flowering plants with the help of a word diagram.

Answer

Reproduction in sexual flower

Question 4.5

Distinguish between Mitosis and Meiosis on the basis of the following three aspects

  • Site of occurrence
  • Nature of division of chromosome
  • Number of cells produced

Explain the following phenomena related to meiotic cell division

  • Separation of chromosome and chromatid
  • Crossing over

Answer

The differences between mitosis and meiosis on the basis of the three aspects:

Aspect Mitosis Meiosis
Site of occurrence Somatic cells Germ cells
Nature of division of chromosome Homologous chromosomes separate Sister chromatids separate
Number of cells produced 2 4

Here are the phenomena related to meiotic cell division:

Separation of chromosome and chromatid

  • Chromosome: A chromosome is a single unit of DNA that contains many genes.
  • Chromatids: Sister chromatids are two identical copies of a chromosome that are joined together at the centromere.

Crossing over

  • Crossing over: A process that occurs during prophase I of meiosis in which genetic material is exchanged between homologous chromosomes.

OR

Distinguish between the cytokinesis of plant cells with the cytokinesis of animal cells on the basis of the following aspects :

  • Process
  • Time of initiation
  • Role of Golgi bodies

Establish the interrelationships among genes, DNA and chromosome.

Answer

Distinguish between the cytokinesis of plant cell with the cytokinesis of animal cell

Aspect Plant cell Animal cell
Process Formation of cell plate Formation of cleavage furrow
Time of initiation After telophase After anaphase
Role of Golgi bodies Releases vesicles containing cell wall material No role

Here are the interrelationships among genes, DNA, and chromosomes in very short:

  • Genes: A gene is a segment of DNA that codes for a specific protein.
  • DNA: DNA is a molecule that contains the genetic instructions for an organism.
  • Chromosome: A chromosome is a structure that contains DNA and proteins.

Question 4.6

Predict what would be the hereditary results in the following cases:

  • One of the parents is thalassaemic and the other is a carrier of the thalassaemic gene.
  • Both of the parents are carriers of the thalassaemic gene

What are the symptoms of Thalassaemia?

Answer

Case 1: One of the parents is thalassemic and the other is a carrier of the thalassemic gene.

  • Child: 50% chance of being thalassemic, 50% chance of being a carrier.

Case 2: Both of the parents are carriers of the thalassemic gene.

  • Child: 25% chance of being thalassemic, 50% chance of being a carrier, 25% chance of being unaffected.

The symptoms of Thalassaemia

  • Pale skin
  • Fatigue
  • Shortness of breath
  • Bone deformities

OR

Tabulate three pairs of opposite traits regarding the seed of the pea plant as selected by Mendel. Show the process of sex determination in men with the help of a checkerboard.

Answer

The three pairs of opposite traits regarding the seed of the pea plant as selected by Mende

Trait Dominant allele Recessive allele
Seed colour Yellow (Y) Green (y)
Flower colour Purple (P) White (p)
Pod shape Round (R) Constricted (r)

Sex determination in men

sex determination

Sex determination is the process by which an individual is identified as male or female. In humans and most animals, sex is determined by the presence or absence of specific sex chromosomes. Females typically have two X chromosomes (XX), while males have one X and one Y chromosome (XY). The presence of the Y chromosome determines maleness, while the absence of it results in femaleness. In some species, environmental factors may also play a role in sex determination. For example, in some reptiles, the temperature of the egg incubation determines the sex of the offspring.

Group – ‘E’

(For External Candidates Only)

5. Answer any four questions: [1×4=4]

Question 5.1

Write a feature of connective tissue.

Answer

Connective tissue is a type of tissue that binds, supports, and protects other tissues and organs in the body.

Question 5.2

Which cell organelle is termed the “powerhouse” of the cell?

Answer

The mitochondria are the cell organelle that is termed as the “powerhouse” of the cell.

Question 5.3

Write a function of Collenchyma tissue.

Answer

Collenchyma tissue is a type of plant tissue that provides support and flexibility to plant organs.

Question 5.4

Give an example of an ornithophilous flower.

Answer

An ornithophilous flower is a flower that is pollinated by birds. Some examples of ornithophilous flowers include:

  • The Bird of paradise flower
  • The orchid flower
  • The hibiscus flower

Question 5.5

Give an example of an amylolytic enzyme.

Answer

An amylolytic enzyme is an enzyme that breaks down starch into sugar. Some examples of amylolytic enzymes include:

  • Amylase
  • Maltase
  • Isomaltase

6. Answer any three questions : [2×3=6]

Question 6.1

Name any two structural parts of the Neurone.

Answer

The two structural parts of a neurone are:

  • Dendrites: These are short, branching projections that extend from the cell body of the neurone. They receive signals from other neurones.
  • Axon: This is a long, single projection that extends from the cell body of the neurone. It carries signals away from the cell body.

Question 6.2

Write the name of two non-nitrogenous excretory products of the plant.

Answer

Two non-nitrogenous excretory products of the plant are:

  • Oxygen: This is produced during photosynthesis.
  • Water vapour: This is released through transpiration.

Question 6.3

Write one function for each ribosome and lysosome.

Answer

One function for each ribosome and lysosome

  • Ribosome: Ribosomes are the organelles that are responsible for protein synthesis.
  • Lysosome: Lysosomes are the organelles that are responsible for digesting cellular waste.

Question 6.4

Name two endangered animals of West Bengal.

Answer

Two endangered animals of West Bengal are:

  • Gangetic dolphin
  • Indian rhinoceros

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