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(Section A: Biology)

Q1. Select the group in which all organisms have the same mode of nutrition.

A. Cuscuta, yeast, legumes, leeches and tapeworm
B. Cactus, ticks, lice, leeches and cow
C. Cuscuta, ticks, lice, leeches and tapeworm
D. Cactus, grass, lice, lion and tapeworm

Correct Answer: C
Explanation:
All the organisms in Option C are parasitic.

  • Cuscuta (a parasitic plant)
  • Ticks, lice, leeches, tapeworm – all are parasitic animals that derive nutrition from a host without killing it.
Q2.Which of the following options indicates the products formed after breakdown of the glucose in our muscle cells when there is lack of oxygen?

A. Ethanol + carbon dioxide + Energy
B. Lactic acid + Energy
C. Lactic acid + carbon monoxide + Energy
D. Carbon dioxide + Water + Energy

Correct Answer: B
Explanation:
In anaerobic respiration in muscle cells, glucose is broken down to lactic acid, releasing a small amount of energy:

Glucose → Lactic Acid + Energy

Q3. Which of the following is a correct combination of function and part of the brain?

A. Posture and balance: Cerebrum
B. Salivation: Medulla in midbrain
C. Hunger: Pons in hindbrain
D. Blood pressure: Medulla in hindbrain

Correct Answer: D
Explanation:
The medulla oblongata in the hindbrain controls involuntary functions, including blood pressure, heartbeat, and breathing.

Q4. The blood glucose level in a patient was very high. It may be due to inadequate secretion of:

A. growth hormone from pituitary gland
B. oestrogen from ovary
C. insulin from pituitary gland
D. insulin from pancreas

Correct Answer: D
Explanation:
High blood glucose is a sign of diabetes, caused by insufficient insulin production by the pancreas.

Q5. In a cross between black furred rabbit (B) and white furred rabbit (b), all offspring were found to have black fur. What can be inferred about the genetic makeup of the parent rabbits?

A. BB × bb
B. Bb × Bb
C. Bb × bb
D. bb × bb

Correct Answer: A
Explanation:
If all offspring are black-furred, black is dominant.
BB (black) × bb (white) = all offspring Bb (black)

Q6. Which are the correct statements related to ozone?

(i) Ozone layer helps in increasing the UV radiations reaching earth.
(ii) Ozone is a deadly poison.
(iii) Ozone layer shields the earth from UV radiations.
(iv) Ozone layer prevents UV rays which cause skin cancer.
(v) Ozone is formed with the help of Chloroflurocarbons.

A. (i), (ii), (iii)
B. (ii), (iii), (iv)
C. (iii), (iv), (v)
D. (i), (iv), (v)

Correct Answer: B
Explanation:
Ozone is toxic at ground level, hence (ii) is true.
It absorbs UV rays, thus (iii) and (iv) are correct.
But CFCs destroy ozone, not help form it, so (v) is incorrect.
Ozone is toxic at ground level, hence (ii) is true.
It absorbs UV rays, thus (iii) and (iv) are correct.
But CFCs destroy ozone, not help form it, so (v) is incorrect.

Q7. Which of the following human activities has resulted in an increase of non-biodegradable substances?

A. Organic farming
B. Tree plantation
C. Use of plastic for packaging
D. Composting of kitchen waste

Correct Answer: C
Explanation:
Plastic is non-biodegradable and accumulates in nature, causing pollution.

The following two questions consist of two statements – Assertion (A) and Reason (R). Answer these questions by selecting the appropriate option given below:
A. Both A and R are true, and R is the correct explanation of A.
B. Both A and R are true, and R is not the correct explanation of A.
C. A is true but R is false.
D. A is false but R is true.

Q8. Assertion (A): Tallness of a pea plant is controlled by an enzyme.
Reason (R): The gene for that enzyme makes proteins which help the plant to be tall.

Answer: A. Both A and R are true, and R is the correct explanation of A.

Explanation: Genes encode enzymes that regulate plant growth. The presence of such enzymes leads to tallness in pea plants.

Q9. Assertion (A): Vulture will always have the least amount of pesticides in a food chain.
Reason (R): Vulture occupies the last trophic level and it gets only 10% of energy of the previous trophic level.

Answer: D. A is false but R is true.

Explanation: Vultures actually accumulate more pesticides due to biomagnification. While energy transfer is only 10%, pesticide concentration increases up the food chain.

Q10. Unlike animals, plants do not have any excretory products as they do not eat food. Comment upon the statement with justification.

Answer:

The statement is not entirely true. While it is correct that plants do not consume food in the same way animals do, they still undergo metabolic processes such as photosynthesis and respiration. These processes generate waste products like oxygen, carbon dioxide, water vapor, and other compounds like resins, gums, and oils. These are excreted through different mechanisms like diffusion through stomata, storage in old tissues, or deposition in bark. Hence, plants do produce excretory products, but their excretory system is different from that of animals.

Q11. Students to attempt either option A or B.

Option A: How many chambers are there in the heart of the following organisms? How is mixing of oxygenated and deoxygenated blood prevented in their body?

  1. Fishes: 2 chambers (1 atrium, 1 ventricle). Blood passes through the heart only once during a complete cycle (single circulation). Oxygenated and deoxygenated blood do not mix because only deoxygenated blood enters the heart.
  2. Humans: 4 chambers (2 atria, 2 ventricles). There is complete separation of oxygenated and deoxygenated blood by the septum. This prevents mixing and maintains efficient double circulation.

OR

Option B: Explain the mechanism by which the water is transported in plants?

Answer:

Water is transported in plants through xylem tissue by a process known as transpiration pull. Roots absorb water from the soil by osmosis. This water moves upward due to capillary action and root pressure. Transpiration from leaf surfaces creates a negative pressure, pulling water upward in a continuous column. This cohesive and adhesive property of water enables its transport even in tall trees.

Q12. About 100 acres of forest land was declared as Natural reserve park. The following organisms were predominant in the Natural reserve park:

rabbit, frog, grass, fish, fox, water insects, zebra, peacock, snake, trees, bird, owl, insects, tiger, vulture, duck

Create a food web comprising two separate food chains with different producers by using the above data.

Answer:

Food Chain 1:
Grass → Rabbit → Fox → Vulture

Food Chain 2:
Water Plants (algae) → Water Insects → Fish → Duck → Owl

These food chains form part of a food web where different organisms are interconnected through feeding relationships. The food web helps in maintaining ecological balance in the natural reserve park.

Q13. Draw and explain how the nerve cells help in transmission of impulses?

Answer:

Nerve cells (neurons) are specialized to transmit electrical impulses. A neuron consists of:

  • Dendrites: Receive electrical messages from other neurons.
  • Cell body: Contains the nucleus and cytoplasm.
  • Axon: Transmits impulses away from the cell body.
  • Axon terminals: Pass signals to next neuron or muscle cell through synapse.

The impulse travels in the form of an electrical signal along the axon, and at the synapse, chemicals (neurotransmitters) help pass the signal to the next cell.

Q14. In a genetic experiment, plants with pure round green seeds (RRyy) were crossed with plants with wrinkled yellow seeds (rrYY).

  1. Show the gametes formed when F1 was self-pollinated.

Answer:

F1 generation genotype: RrYy (Round Yellow)
Gametes formed: RY, Ry, rY, ry

  1. A total of 144 seeds were produced which developed into saplings. Show the ratio in which these traits are independently inherited in these 144 saplings.

Answer:

This is a dihybrid cross showing independent assortment.

Phenotypic ratio of offspring: 9 (Round Yellow) : 3 (Round Green) : 3 (Wrinkled Yellow) : 1 (Wrinkled Green)

Using this ratio for 144 saplings:

  • Round Yellow = 9/16 × 144 = 81
  • Round Green = 3/16 × 144 = 27
  • Wrinkled Yellow = 3/16 × 144 = 27
  • Wrinkled Green = 1/16 × 144 = 9

Q15. Neha consumed boiled sweet potatoes and boiled eggs for breakfast. Help her to understand some steps in the process of digestion of the food taken by her by answering the questions given below.

Attempt either subpart A or B.

A. Which of these food items is rich in proteins? In which part of the alimentary canal is the digestion of this component initiated? Name the enzymes, conditions required and the glands associated with the digestion here.

Answer:

Boiled eggs are rich in proteins. Protein digestion starts in the stomach. The stomach secretes pepsin enzyme, which breaks down proteins into peptides. Pepsin works in acidic conditions created by HCl secreted by gastric glands.

OR

B. Which of these food items contains fats? How is it digested?

Answer:

Egg yolk contains fats. Fat digestion occurs in the small intestine. Bile from liver emulsifies fats, and pancreatic lipase breaks them down into fatty acids and glycerol.

C. Which of these food items is rich in starch? How is its digestion initiated?

Answer:

Boiled sweet potatoes contain starch. Starch digestion begins in the mouth. Salivary glands release amylase enzyme, which breaks down starch into maltose.

D. The figure given below represents parts of the human alimentary canal. Which of these parts will have the maximum amount of digested food as soon as the process of digestion is completed?

Answer: Part O (Small intestine) has the maximum digested food as it is the main site of digestion and absorption.

D (for visually impaired): How will the digested food be taken up by the alimentary canal?

Answer: The digested food is absorbed through the walls of the small intestine into the bloodstream and then transported to body cells.

Q16. Attempt either option A or B.

Option A: Puneet wanted to grow banana plants.

  1. Based on your knowledge on plant reproduction should he opt for seeds or any alternate method of reproduction. Justify your answer.

Answer: Puneet should opt for an alternate method of reproduction such as vegetative propagation instead of seeds. Banana plants are typically propagated through suckers (underground stems). This is because cultivated bananas are usually sterile and do not produce viable seeds. Vegetative propagation ensures faster growth and identical offsprings.

  1. Offsprings of a banana plant usually show very little variation. What causes variation and are variations good or bad? Justify.

Answer: Variations arise due to genetic changes during sexual reproduction or mutations. In asexually propagated plants like bananas, variation is minimal. However, variation is beneficial in a population as it helps organisms adapt to environmental changes and increases chances of survival during disease outbreaks or climate shifts.

Option B: Annie was conducting research on the number of fruits produced by watermelon under different conditions. She grew 25 watermelon plants each in both glass house A and B. She introduced pollinators in glass house A only.

  1. What difference will she observe in the number of fruits produced in the two glass houses? Explain with reason.

Answer: Glass house A will show more fruits compared to glass house B. This is because pollinators such as bees and butterflies help in pollination by transferring pollen from male to female flowers. Without pollinators in glass house B, pollination and hence fruit formation will be limited.

  1. List 3 changes that will occur in a flower once it gets fertilized.

Answer:

  1. The ovary develops into a fruit.
  2. The ovules develop into seeds.
  3. The petals, sepals, stamens, and style usually wither and fall off.

Section B
Section C