2024 – Biological Sciences 

SECTION – I

Each question carries 2 marks

1.Write any two materials required to conduct an experiment to observe the internal structure of the mammalian heart.

Answer:

  1. Dissecting tools (e.g., scissors, scalpel)
  2. Preserved mammalian heart (e.g., from a cow or pig)

2.Write any two biological principles to be followed by the farmers in your surroundings for controlling pests.

Answer:

  1. Biological control – Using natural predators or parasites to control pest populations (e.g., introducing ladybugs to control aphids).
  2. Crop rotation – Changing the types of crops grown in a particular field to prevent pest buildup and reduce the likelihood of pest infestation.

3.What will happen if moisture and hairs are absent in the nasal cavity of human beings? 

Answer:
If moisture and hairs are absent in the nasal cavity, the inhaled air will not be properly warmed, filtered, or humidified, leading to irritation of the respiratory tract and an increased risk of infections or other respiratory problems.

 

SECTION – II

Each question carries 4 marks

4.Write four differences between aerobic respiration and anaerobic respiration. 

Answer:

  1. Oxygen requirement:
    • Aerobic respiration requires oxygen.
    • Anaerobic respiration does not require oxygen.
  2. End products:
    • Aerobic respiration produces carbon dioxide and water.
    • Anaerobic respiration produces lactic acid or ethanol and carbon dioxide.
  3. Energy released:
    • Aerobic respiration releases more energy (ATP).
    • Anaerobic respiration releases less energy (ATP).
  4. Occurrence:
    • Aerobic respiration occurs in the mitochondria of cells.
    • Anaerobic respiration occurs in the cytoplasm of cells.
5.Explain any two artificial propagation methods you observed in your daily life with examples. 

Answer:

  1. Cutting: Involves cutting a piece of a plant and encouraging it to grow roots. Example: Rose cutting, where a part of a stem is cut and placed in soil to develop roots.
  2. Grafting: Involves joining two plants together to grow as one. Example: Grafting of mango trees, where a bud of a desired variety is grafted onto a rootstock of a different variety to promote growth.
6.Observe the picture given below and answer the following questions.
(i) Name the scientist who conducted the experiment given in the above picture.
(ii) Which phytohormone was discovered by the above experiment?
(iii) Write the effect of the phytohormone identified in the above experiment on plants.
(iv) In the above experiment, name the material placed on the cut coleoptile tips of the oat seedling.

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Answer:
(i) The scientist who conducted the experiment is Charles Darwin.
(ii) The phytohormone discovered by the above experiment is Auxin.
(iii) The effect of auxin on plants is that it promotes cell elongation and growth in the direction of light (phototropism).
(iv) In the experiment, the material placed on the cut coleoptile tips of the oat seedling is a block of gelatin or agar containing auxin.

 SECTION – III

Each question carries 6 marks

 7. Explain the evidences of Evolution with examples.

The theory of evolution is supported by multiple lines of evidence from various fields of science, providing a strong foundation for understanding the development of life on Earth. Here are the major types of evidence:

  1. Fossil Evidence: Fossils are preserved remains of organisms that lived in the past. By studying fossils, scientists can observe how organisms have changed over time. For example, the evolution of horses is documented through fossils that show gradual changes in size, teeth, and limb structure, indicating adaptation to different environments.
  2. Comparative Anatomy: The study of the anatomical structures of different species reveals similarities that suggest common ancestry. For example:
    • Homologous structures: These are body parts that are structurally similar in different species, but may have different functions. An example is the forelimbs of humans, bats, and whales, which have similar bone structures but serve different purposes (grasping, flying, swimming).
    • Vestigial structures: These are body parts that no longer serve a critical function but were functional in ancestors. An example is the appendix in humans or the pelvic bones in whales.
  3. Comparative Embryology: The study of embryos across different species shows that early developmental stages are very similar. For instance, embryos of humans, chickens, and fish all show similar features like gill slits and a tail, suggesting a common evolutionary ancestor.
  4. Molecular Evidence: Similarities in DNA, RNA, and protein sequences provide evidence for evolution. For example, humans and chimpanzees share about 98% of their DNA, indicating a common ancestor. The more closely related two species are, the more similar their genetic material is.
  5. Biogeographical Evidence: The distribution of species across the planet supports evolutionary theory. For instance, the unique species found on isolated islands like the Galápagos Islands, such as Darwin’s finches, provide insights into how species evolve differently based on their environments.

8. Draw a labelled diagram of the internal structure of the human kidney and explain the structure.

Labelled Diagram of the Human Kidney:

Draw a well labelled diagram of L.S. of the human kidney?
Explanation of the Structure: 
The human kidney is a vital organ responsible for filtering blood, removing waste products, and regulating water and salt balance.
Here are the major parts of the kidney:
  1. Renal Capsule: The outermost layer of the kidney, providing protection.
  2. Renal Cortex: The outer region of the kidney, which contains the glomeruli and renal tubules. It is involved in filtration.
  3. Renal Medulla: The inner region that contains the renal pyramids. These structures house the loops of Henle and collecting ducts, which play roles in the reabsorption of water and salts.
  4. Renal Pyramids: Cone-shaped structures within the medulla, each of which contains the nephron’s loop of Henle.
  5. Renal Papilla: The tip of each pyramid, which drains urine into the renal calyces.
  6. Renal Pelvis: A funnel-shaped structure that collects urine from the renal papillae and channels it into the ureter.
  7. Ureter: The duct that transports urine from the renal pelvis to the bladder.

9. Explain the procedure and precautions of the experiment to prove that Oxygen is evolved during Photosynthesis.

Objective: To demonstrate that oxygen is released during the process of photosynthesis.

Materials:

  • A water plant (e.g., Elodea or Pondweed)
  • A beaker or container with water
  • A test tube
  • A lamp or light source
  • Sodium bicarbonate (to increase carbon dioxide concentration)
  • Stopwatch

Procedure:

  1. Fill a beaker with water and add a small amount of sodium bicarbonate to increase the carbon dioxide concentration.
  2. Place a water plant, like Elodea, in the beaker, ensuring the plant is submerged in water.
  3. Invert a test tube over the plant in the beaker, ensuring the open end is submerged in water.
  4. Place the beaker under a light source (lamp) and allow the plant to undergo photosynthesis.
  5. After some time, observe the formation of bubbles (oxygen) around the plant.
  6. The gas collected in the test tube is oxygen, which is being released as a byproduct of photosynthesis.

Precautions:

  1. Ensure the water is free of impurities that might interfere with the experiment.
  2. Use a consistent light source to ensure that all plants receive equal light intensity.
  3. Ensure the test tube is completely submerged to avoid air leakage and contamination.
  4. Perform the experiment at a suitable temperature as temperature affects the rate of photosynthesis.

Conclusion: The experiment demonstrates that oxygen is produced during photosynthesis as gas bubbles are observed escaping from the submerged plant, collected in the inverted test tube. This proves that oxygen is a byproduct of the process where plants use light to convert carbon dioxide and water into glucose and oxygen.