Nutrition in Living Beings - CBSE Class 10 Biology – Long Answer Questions

Medium Level (Application & Explanation)

Answer:

Living organisms require energy not only for active movements like running or playing but also during periods of rest.
Even when a person is sitting or sleeping, the body continues to perform essential functions such as breathing, blood circulation, digestion, and cell repair.
Muscle contractions, nerve impulses, and enzyme production all consume energy.
For example, athletes need extra energy for intense training, while children require more to support growth and development.
Plants need constant energy for photosynthesis, even though they do not move, and to synthesize essential molecules for growth.
Therefore, energy is the driving force for all life processes, making it essential at every moment.

Answer:

Autotrophic nutrition refers to the process by which organisms make their own food using inorganic sources.
- Example: Green plants use sunlight, carbon dioxide, and water to prepare food through photosynthesis. Certain bacteria and algae are also autotrophic.
Heterotrophic nutrition describes organisms that depend on other organisms for their food.
- Examples:
  - Herbivores like cows eat grass and other plants.
  - Carnivores like lions eat other animals.
  - Decomposers, such as fungi, absorb nutrients from dead and decaying organic matter.
Key difference: Autotrophs convert inorganic substances into organic food, whereas heterotrophs utilize pre-formed organic food from plants or animals.

Answer:

Photosynthesis is the process by which green plants, certain bacteria, and algae convert solar energy into chemical energy.
The process takes place in the chloroplasts with the help of chlorophyll.
Plants use carbon dioxide (CO₂) from the air and water (H₂O) from the soil. Under sunlight, these substances react to form glucose (C₆H₁₂O₆) and oxygen (O₂).
The general equation:
6CO₂ + 6H₂O + sunlight → C₆H₁₂O₆ + 6O₂
Glucose serves as an immediate energy source or is stored as starch for later use.
Thus, photosynthesis enables autotrophs to be self-dependent, forming the base of the food chain and providing energy to all living beings directly or indirectly.

Answer:

Chlorophyll, the green pigment in leaves, is essential for capturing sunlight energy, which drives the synthesis of glucose.
Experiment (Variegated Leaf Activity):
- Take a plant with variegated (green and white) leaves and keep it in the dark for three days.
- Expose it to sunlight for around six hours.
- Boil a leaf, immerse in alcohol to remove chlorophyll, and then test with iodine solution.
- Observation: Only the green parts, which contain chlorophyll, turn blue-black with iodine, indicating starch (a product of photosynthesis) is formed there.
This demonstrates chlorophyll's direct involvement in photosynthesis, as only those parts with chlorophyll can manufacture food.

Answer:

Stomata are tiny pores on the surfaces of leaves surrounded by guard cells.
They regulate the entry of carbon dioxide (needed for photosynthesis) and the exit of oxygen (a byproduct).
Stomata open during the day to allow CO₂ to enter and O₂ to exit when photosynthesis is active.
To prevent water loss, especially in hot or dry conditions, guard cells close the stomata.
This balance helps plants optimize photosynthesis while conserving water.
Stomata can also adjust their opening based on environmental conditions, demonstrating their critical role in plant survival.

Answer:

Nitrogen is an essential nutrient for plant growth, required for the synthesis of proteins, nucleic acids (DNA/RNA), and chlorophyll.
In nitrogen-deficient soil:
- Plants show stunted growth with reduced height and leaf size.
- Leaves turn yellowish (chlorosis), especially older leaves, as they can’t synthesize enough chlorophyll.
- The rate of photosynthesis drops, leading to poor energy production.
- Flowers and fruits may not develop properly, impacting reproduction.
- The plant becomes weak and more susceptible to disease.
Thus, nitrogen deficiency severely affects the plant's growth, metabolism, and productivity.

Answer:

Desert plants face intense heat and water scarcity.
Their stomata show unique adaptations such as:
- Fewer stomata or stomata restricted to the leaf underside to reduce water loss.
- Opening stomata at night (CAM photosynthesis), allowing CO₂ uptake in cooler conditions, reducing evaporation.
- Some desert plants have sunken stomata or are covered with hairs to minimize direct exposure.
- In extreme drought, stomata may remain closed for extended periods.
These adaptations ensure minimal water loss while still permitting necessary gas exchange, enabling survival in harsh climates.

Answer:

Petroleum jelly blocks the stomata on the leaf surface.
Consequences:
- Gas exchange is obstructed: No entry of CO₂ or exit of O₂.
- Photosynthesis rate drops: CO₂ is essential for making glucose; without it, the process halts.
- Transpiration stops: Water movement and cooling mechanisms are hindered.
- The plant may overheat and become stressed.
- Long-term: The plant will eventually stop growing and may die due to lack of energy and accumulation of waste gases.
This highlights the importance of open stomata for photosynthesis and plant health.

Answer:

When a plant is kept in the dark, even if carbon dioxide is available, photosynthesis cannot occur as sunlight is absent.
Results of the starch test will show no blue-black coloration, indicating the absence of starch formation.
This outcome proves that both sunlight and carbon dioxide are essential for photosynthesis.
The experiment demonstrates the interdependence of factors needed for the process and helps in understanding why plants do not photosynthesize at night.

Answer:

Photosynthesis is the process by which plants produce food (glucose) using sunlight, CO₂, and water.
Plants form the base of the food chain, providing energy to herbivores, which in turn support carnivores.
The oxygen released during photosynthesis is vital for respiration in almost all living organisms.
Photosynthesis helps maintain the balance of atmospheric gases by absorbing CO₂ and releasing O₂.
Fossil fuels (coal, oil) originate from ancient plant matter—products of photosynthesis.
Human food, oxygen supply, and even materials are all directly or indirectly dependent on this process.
Thus, photosynthesis supports the existence and sustainability of life on Earth.