Class 10 Board examination- Biological science mock test paper

Class 10 Board Examination — Biological Science Mock Test Paper — 2 Time: 3 Hours | Maximum Marks: 60

General Instructions: 1. Section A contains MCQs (1 mark each) 2. Section B contains Short Answer questions (2 marks each) 3. All questions are compulsory 4. Draw neat diagrams wherever necessary

SECTION A — Multiple Choice Questions

(1 Mark Each | 10 × 1 = 10 Marks)

Q1. Which of the following is the correct path of urine in the human excretory system? (a) Kidney → Urethra → Ureter → Urinary bladder (b) Kidney → Ureter → Urinary bladder → Urethra (c) Kidney → Urinary bladder → Ureter → Urethra (d) Kidney → Ureter → Urethra → Urinary bladder

Q2. The process by which green plants prepare their food is called: (a) Respiration (b) Transpiration (c) Photosynthesis (d) Digestion

Q3. Which of the following hormones regulates blood sugar levels? (a) Adrenaline (b) Thyroxine (c) Insulin (d) Testosterone

Q4. The male reproductive part of a flower is called: (a) Pistil (b) Sepal (c) Stamen (d) Ovary

Q5. Which of the following is an example of vegetative propagation? (a) Seed formation (b) Budding in yeast (c) Potato growing from tuber (d) Spore formation in ferns

Q6. In a monohybrid cross between a tall (TT) and a dwarf (tt) pea plant, the phenotypic ratio in F2 generation is: (a) 1:2:1 (b) 3:1 (c) 1:1 (d) 9:3:3:1

Q7. The evolutionary theory of natural selection was proposed by: (a) Gregor Mendel (b) Jean-Baptiste Lamarck (c) Charles Darwin (d) Hugo de Vries

Q8. Which of the following is a greenhouse gas? (a) Nitrogen (b) Oxygen (c) Carbon dioxide (d) Argon

Q9. The transfer of energy through a food chain follows which law? (a) Law of conservation of mass (b) 10% law of energy transfer (c) Law of limiting factors (d) Law of independent assortment

Q10. Which of the following is an example of an ex-situ conservation method? (a) Wildlife sanctuary (b) National park (c) Biosphere reserve (d) Zoological park

SECTION B — Short Answer Questions

(2 Marks Each | 15 × 2 = 30 Marks)

Q11. What is nutrition? Differentiate between autotrophic and heterotrophic nutrition with one example each.

Q12. Describe the role of the following organs in human digestion: (i) Stomach (ii) Small intestine

Q13. What is double circulation? Why is it necessary in human beings?

Q14. What is the difference between breathing and respiration? State the steps involved in cellular respiration.

Q15. What are stomata? State their two functions in a plant.

Q16. Explain the structure and function of a neuron with a neat labelled diagram description.

Q17. What is a reflex action? Describe the reflex arc with a suitable example.

Q18. Differentiate between sexual and asexual reproduction. Give two examples of each.

Q19. What is the significance of DNA copying during reproduction? What happens if errors occur during copying?

Q20. Explain Mendel's Law of Independent Assortment with a suitable example.

Q21. What is the difference between homologous and analogous organs? Give one example of each.

Q22. Define food chain and food web. Give one example of a food chain with four trophic levels.

Q23. What are the causes and effects of ozone layer depletion? State two measures to prevent it.

Q24. What is bioaccumulation? How does it affect organisms at higher trophic levels?

Q25. State any four human activities that have led to environmental degradation and suggest one solution for each.

ANSWERS

Section A — Answers

A1. (b) Kidney → Ureter → Urinary bladder → Urethra

A2. (c) Photosynthesis

A3. (c) Insulin

A4. (c) Stamen

A5. (c) Potato growing from tuber

A6. (b) 3:1

A7. (c) Charles Darwin

A8. (c) Carbon dioxide

A9. (b) 10% law of energy transfer

A10. (d) Zoological park

Section B — Answers

A11. Nutrition is the process by which organisms obtain and utilise food for energy, growth, repair, and maintenance of body functions.

Autotrophic nutrition: Organisms that prepare their own food using simple inorganic substances like CO₂ and water in the presence of sunlight and chlorophyll. Example: Green plants (e.g., mango tree)

Heterotrophic nutrition: Organisms that depend on other organisms for their food as they cannot prepare their own. Example: Animals and fungi (e.g., human beings, mushroom)

A12. (i) Stomach: The stomach is a muscular bag-like organ that stores food temporarily. It secretes gastric juice containing hydrochloric acid (HCl), pepsin, and mucus. HCl makes the medium acidic and kills harmful bacteria. Pepsin digests proteins into peptides. Mucus protects the inner lining of the stomach from the acidic medium.

(ii) Small intestine: It is the longest part of the digestive system where complete digestion of carbohydrates, proteins, and fats takes place. It receives bile from the liver and pancreatic juice from the pancreas. The inner walls have finger-like projections called villi that increase the surface area for absorption of digested food into the bloodstream.

A13. Double circulation is the type of blood circulation in which blood passes through the heart twice in one complete circuit of the body — once through the pulmonary circuit (heart to lungs and back) and once through the systemic circuit (heart to body and back).

Necessity in human beings: Since human beings are warm-blooded animals, they need a constant and sufficient supply of energy to maintain their body temperature and carry out various activities. Double circulation ensures that oxygenated and deoxygenated blood are completely separated, preventing mixing, and ensuring that all body tissues receive a rich supply of oxygenated blood efficiently.

A14. Breathing: It is a physical process involving the intake of oxygen from the environment and the release of carbon dioxide. It involves the movement of the chest and diaphragm. It is also called external respiration.

Respiration: It is a biochemical process occurring inside cells where glucose is broken down to release energy in the form of ATP. It is also called cellular or internal respiration.

Steps involved in cellular respiration:

Glycolysis — Glucose (6C) is broken down into pyruvate (3C) in the cytoplasm. 2 ATP molecules are produced.
Krebs cycle (in mitochondria) — Pyruvate is fully oxidised to CO₂ and H₂O, producing more ATP.
Electron transport chain — Maximum ATP is produced using the electrons released during the above steps.

A15. Stomata are tiny pores present on the surface of leaves (mainly the lower epidermis) surrounded by two kidney-shaped guard cells that regulate the opening and closing of the pore.

Two functions of stomata:

Gaseous exchange: Stomata allow the exchange of gases (CO₂ and O₂) between the plant and the atmosphere, which is essential for photosynthesis and respiration.
Transpiration: Stomata allow the evaporation of excess water from the plant in the form of water vapour, which helps in the upward movement of water and minerals from roots to leaves and also cools the plant.

A16. A neuron (nerve cell) is the structural and functional unit of the nervous system.

Structure (describe diagram with labels):

Cell body (cyton): Contains the nucleus and cytoplasm. It is the metabolic centre of the neuron.
Dendrites: Short, branched extensions from the cell body that receive nerve impulses from other neurons or sensory receptors.
Axon: A long, slender projection that carries nerve impulses away from the cell body to other neurons or effector organs.
Myelin sheath: A fatty covering around the axon that insulates and speeds up nerve impulse transmission.
Synaptic knobs: Terminal ends of the axon that release neurotransmitters to pass impulses to the next neuron.

Function: A neuron receives, processes, and transmits electrical impulses (nerve signals) throughout the body, enabling quick responses to stimuli.

(Draw and label: dendrites, cell body/cyton, nucleus, axon, myelin sheath, node of Ranvier, synaptic knob)

A17. Reflex action is a spontaneous, involuntary, and rapid response to a stimulus that is controlled by the spinal cord without the involvement of the brain.

Reflex arc: The pathway taken by a nerve impulse during a reflex action is called a reflex arc.

Example — Withdrawing hand from a hot object:

Receptor (skin of hand) detects heat (stimulus).
Sensory neuron carries the impulse to the spinal cord.
The spinal cord (nerve centre) processes the information and sends a response signal.
Motor neuron carries the response impulse to the effector (muscles of the hand).
Effector (muscles) contract and the hand is pulled away.

The pathway is: Receptor → Sensory neuron → Spinal cord → Motor neuron → Effector (muscle)

A18.

	Sexual Reproduction	Asexual Reproduction
Gametes	Involves fusion of male and female gametes	Does not involve gametes
Parents	Two parents usually required	Single parent is sufficient
Variation	Offspring show genetic variation	Offspring are genetically identical (clones)
Process	Slow and complex	Fast and simple

Examples of sexual reproduction: Humans, flowering plants (through seeds)

Examples of asexual reproduction: Budding in Hydra, binary fission in Amoeba, spore formation in Rhizopus, regeneration in Planaria

A19. DNA copying is essential during reproduction because DNA carries all the genetic information (blueprint) of an organism. When cells divide during reproduction, DNA replication ensures that each new cell receives an exact copy of the genetic information, maintaining the characteristics of the species from generation to generation.

If errors occur during DNA copying: These errors are called mutations. They lead to changes in the DNA sequence which may result in altered proteins or traits. Minor errors may cause slight variations in offspring, which can be beneficial (leading to evolution and adaptation), neutral, or harmful. Severe mutations can cause genetic disorders or may be lethal to the offspring. Over many generations, accumulated variations through errors in DNA copying contribute to the process of evolution.

A20. Mendel's Law of Independent Assortment: When two pairs of contrasting traits are considered simultaneously, the alleles of one pair of traits assort (separate) independently of the alleles of the other pair during gamete formation.

Example — Dihybrid cross: Mendel crossed pea plants with round yellow seeds (RRYY) with wrinkled green seeds (rryy).

F1 generation: All seeds were round and yellow (RrYy) — round and yellow being dominant.

When F1 plants were self-pollinated (RrYy × RrYy), four types of offspring appeared in F2 in the ratio 9:3:3:1:

9 Round Yellow (R_Y_)
3 Round Green (R_yy)
3 Wrinkled Yellow (rrY_)
1 Wrinkled Green (rryy)

This shows that seed shape and seed colour genes assorted independently of each other during gamete formation.

A21. Homologous organs: Organs that have the same basic structural plan and origin (same ancestral origin) but are adapted to perform different functions in different organisms. Example: The forelimbs of a human (for grasping), a whale (for swimming), a bat (for flying), and a horse (for running) are homologous organs. They indicate divergent evolution.

Analogous organs: Organs that have different structural plans and origins but perform the same function in different organisms. Example: The wings of a bird (made of bones and feathers) and the wings of an insect (made of chitin) are analogous organs. They indicate convergent evolution.

A22. Food chain: A linear sequence showing the transfer of energy from one organism to another through feeding relationships is called a food chain. Each organism in the chain represents a trophic level.

Food web: A network of interconnected food chains in an ecosystem is called a food web. It gives a more realistic picture of feeding relationships in nature.

Example of a food chain with four trophic levels: Grass → Grasshopper → Frog → Snake

Trophic levels:

Grass — Producer (1st trophic level)
Grasshopper — Primary consumer (2nd trophic level)
Frog — Secondary consumer (3rd trophic level)
Snake — Tertiary consumer (4th trophic level)

A23. Causes of ozone layer depletion: The main cause is the release of chlorofluorocarbons (CFCs) from refrigerators, air conditioners, and aerosol sprays. CFCs react with ozone (O₃) in the stratosphere and break it down, thinning the ozone layer.

Effects of ozone layer depletion:

Increased ultraviolet (UV) radiation reaching the Earth's surface causes skin cancer, cataracts, and weakened immune systems in humans.
UV radiation damages phytoplankton in oceans, disrupting aquatic food chains and reducing marine biodiversity.

Two measures to prevent ozone depletion:

Banning or phasing out the production and use of CFCs and other ozone-depleting substances globally (as done under the Montreal Protocol).
Using CFC-free refrigerants and eco-friendly alternatives in air conditioners and refrigerators.

A24. Bioaccumulation (also called biological magnification or biomagnification) is the progressive increase in the concentration of harmful, non-biodegradable substances (such as pesticides like DDT, heavy metals like mercury) in the bodies of organisms at each successive trophic level of a food chain.

Effect on organisms at higher trophic levels: Since these substances cannot be broken down or excreted by the body, they accumulate in fatty tissues and become more and more concentrated as they move up the food chain. Organisms at higher trophic levels (such as large fish, birds of prey, and humans) accumulate the highest concentrations of these toxic substances. This causes serious health problems including reproductive failure, nerve damage, hormonal disruption, weakening of eggshells in birds, and even death in severe cases.

Example: DDT sprayed on crops → absorbed by insects → eaten by small fish → eaten by large fish → eaten by fish-eating birds. The concentration of DDT increases at each level, causing reproductive problems in top predators like eagles and ospreys.

A25. Four human activities causing environmental degradation and their solutions:

Deforestation — Large-scale cutting of trees for agriculture, urbanisation, and industry destroys habitats, causes soil erosion, and increases CO₂ levels. Solution: Practice afforestation and reforestation; adopt sustainable forestry practices.
Industrial pollution — Discharge of untreated chemical waste into rivers and emission of harmful gases from factories causes water, air, and soil pollution. Solution: Industries must treat their waste (effluents) before disposal and install pollution control devices like scrubbers in chimneys.
Use of chemical pesticides and fertilisers — Excessive use in agriculture leads to soil degradation, water pollution, and bioaccumulation in food chains. Solution: Promote organic farming and the use of biological pest control methods instead of chemical pesticides.
Burning of fossil fuels — Burning of coal, petrol, and diesel in vehicles and power plants releases CO₂, SO₂, and other greenhouse gases, leading to global warming and acid rain. Solution: Shift to renewable energy sources such as solar, wind, and hydroelectric power, and promote the use of electric vehicles.

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