E X E R C I S E S CHAPTER 5 Life Processes SCIENCE NCERT TEXTBOOK (CBSE) CLASS 10:

 E X E R C I S E S  

CHAPTER  5  Life Processes


1. The kidneys in human beings are a part of the system for:

The kidneys are part of the excretory system, which helps in the removal of waste products and excess substances from the body, primarily through the process of urine formation.

Answer: (c) Excretion

2. The xylem in plants is responsible for:

The xylem in plants is responsible for the transport of water and minerals from the roots to other parts of the plant.

Answer: (a) Transport of water

3. The autotrophic mode of nutrition requires:

Autotrophic nutrition, like in plants, requires:

  • Carbon dioxide and water for the process of photosynthesis.
  • Chlorophyll to capture light energy.
  • Sunlight as the energy source.

Therefore, all of the above are necessary for autotrophic nutrition.

Answer: (d) All of the above

4. The breakdown of pyruvate to give carbon dioxide, water, and energy takes place in:

The breakdown of pyruvate occurs in the mitochondria, where the process of aerobic respiration takes place, producing carbon dioxide, water, and energy (ATP).

Answer: (b) Mitochondria

5. How are fats digested in our bodies? Where does this process take place?

Fats are digested by the enzyme lipase. The digestion process begins in the small intestine where bile (produced by the liver) emulsifies the fats, breaking them down into smaller droplets, and lipase further breaks them into fatty acids and glycerol.

6. What is the role of saliva in the digestion of food?

Saliva contains the enzyme salivary amylase, which begins the breakdown of starch (a carbohydrate) into simpler sugars, thus initiating the digestion of food.

7. What are the necessary conditions for autotrophic nutrition and what are its byproducts?

For autotrophic nutrition (photosynthesis), the following conditions are required:

  • Sunlight
  • Water
  • Carbon dioxide
  • Chlorophyll (for absorbing light energy)

The byproducts of this process are oxygen and glucose.

8. What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.

  • Aerobic respiration occurs in the presence of oxygen, produces ATP, carbon dioxide, and water as byproducts.
  • Anaerobic respiration occurs in the absence of oxygen, produces ATP, lactic acid (in animals) or alcohol and carbon dioxide (in yeast and some bacteria).

Organisms that use anaerobic respiration:

  • Yeast (produces ethanol and CO₂)
  • Bacteria (such as lactic acid bacteria)

9. How are the alveoli designed to maximize the exchange of gases?

The alveoli are small, thin-walled, and richly supplied with blood vessels. Their large surface area allows for efficient gas exchange of oxygen and carbon dioxide between the air in the lungs and the blood. Additionally, the thin walls allow gases to diffuse easily.

10. What would be the consequences of a deficiency of hemoglobin in our bodies?

A deficiency in hemoglobin can lead to anemia, a condition where there is a reduced ability to carry oxygen to tissues. Symptoms include fatigue, weakness, and pale skin due to insufficient oxygen supply.

11. Describe double circulation of blood in human beings. Why is it necessary?

In humans, blood circulates in two separate loops:

  • Pulmonary circulation: Blood is pumped from the heart to the lungs, where it is oxygenated, and then returned to the heart.
  • Systemic circulation: Oxygenated blood is pumped from the heart to the rest of the body to deliver oxygen and nutrients, and deoxygenated blood is returned to the heart.

This system is necessary because it ensures that oxygenated and deoxygenated blood are kept separate, improving the efficiency of oxygen delivery to body tissues.

12. What are the differences between the transport of materials in xylem and phloem?

  • Xylem: Transports water and minerals from the roots to other parts of the plant. It is a one-way transport system and moves materials upward.
  • Phloem: Transports food (sugars) produced in the leaves to other parts of the plant. It is a two-way transport system.

13. Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.

  • Alveoli:
    • Structure: Small, thin-walled sacs with a large surface area.
    • Function: Facilitate the exchange of gases (oxygen and carbon dioxide) between the air and blood.
  • Nephrons:
    • Structure: Tiny filtering units in the kidneys with a glomerulus and a renal tubule.
    • Function: Filter blood to remove waste products and excess substances, forming urine.

Both structures maximize surface area for efficient exchange of gases or filtration of blood.

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