Science Chapter - 6: Life Processes

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

(a) nutrition.

(b) respiration.

(c) excretion.

(d) transportation.

Answer: (c) excretion.

2. The xylem in plants are responsible for

(a) transport of water.

(b) transport of food.

(c) transport of amino acids.

(d) transport of oxygen.

Answer: (a) transport of water.

3. The autotrophic mode of nutrition requires

(a) carbon dioxide and water.

(b) chlorophyll.

(c) sunlight.

(d) all of the above.

Answer: (d) all of the above

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

(a) cytoplasm.

(b) mitochondria.

(c) chloroplast.

(d) nucleus.

Answer: (b) mitochondria.

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

Answer: Fats are present in the form of large globules in the small intestine. The small intestine gets the secretions in the form of bile juice and pancreatic juice respectively from the liver and the pancreas. The bile salts break down the large fat globules into smaller globules so that the pancreatic enzymes can easily act on them. This is referred to as emulsification of fats. It takes place in the small intestine

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

Answer: Saliva moistens the food for easy swallowing. It contains a digestive enzyme called salivary amylase, which breaks down starch into sugar.

7. What are the necessary conditions for autotrophic nutrition and what are its by-products?

Answer: Carbon dioxide, water, chlorophyll pigment, and sunlight are the necessary conditions required for autotrophic nutrition. Carbohydrates and Oxygen are the by-products of photosynthesis.

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

Answer:

Aerobic Respiration	Anaerobic Respiration
It occurs in presence of Oxygen.	It occurs in absence of Oxygen.
It occurs in cytoplasm and mitochondria.	It occurs only in cytoplasm.
It releases Carbon Dioxide and Water.	Released products vary.
It yields 36 ATPs.	It yields 2 AAPs.

Anaerobic respiration occurs in the roots of some waterlogged plants, some parasitic worms, animal muscles, and some micro-organisms such as yeasts.

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

Answers: The alveoli are the small balloon-like structures present in the lungs. The walls of the alveoli consist of extensive network of blood vessels. Each lung contains 300−350 million alveoli, making it a total of approximately 700 million in both the lungs. The alveolar surface when spread out covers about 80 meter square of area. This large surface area makes the gaseous exchange more efficient.

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

Answer: Hemoglobin is the respiratory pigment that transports oxygen to the body cells for cellular respiration. Therefore, deficiency of hemoglobin in blood can affect the oxygen supplying capacity of blood. This can lead to deficiency of oxygen in the body cells. It can also lead to a disease called anemia.

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

Answer: The human heart is divided into four chambers − the right atrium, the right ventricle, the left atrium, and the left ventricle.

Flow of blood in the human heart

• The right atrium then contracts and passes the de-oxygenated blood to the right ventricle, through an auriculo-ventricular aperture.
• Then the right ventricle contracts and passes the de-oxygenated blood into the two pulmonary arteries, which pumps it to the lungs where the blood becomes oxygenated. From the lungs, the pulmonary veins transport the oxygenated blood to the left atrium of the heart.
• Then the left atrium contracts and through the auriculo-ventricular aperture, the oxygenated blood enters the left ventricle.
• The blood passes to aorta from the left ventricle. The aorta gives rise to many arteries that distribute the oxygenated blood to all the regions of the body.

Therefore, the blood goes twice through the heart. This is known as double circulation.

Importance of double circulation:

The separation of oxygenated and de-oxygenated blood allows a more efficient supply of oxygen to the body cells. This efficient system of oxygen supply is very useful in warm-blooded animals such as human beings to maintain their body temperature. Hence, they require more oxygen for more respiration so that they can produce more energy to maintain their body temperature.

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

Answer:

Xylem	Phloem
Xylem helps in the transportation of water and minerals.	Phloem helps in the transportation of food.
Water is transported from roots to upward direction.	Food is transported from leaves to all the directions.
Transportation in xylem occurs with the help of simple physical forces like transpiration pull.	Transportation of food in phloem requires energy in the form of ATP.

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

Answer: Structure -

Alveoli are tiny balloon-like structures present inside the lungs.The walls of the alveoli are one cell thick and it contains an extensive network of blood capillaries.

Nephrons are tubular structures present inside the kidneys.Nephrons are made of glomerulus, bowman’s capsule, and a long renal tube. It also contains a cluster of thin-walled capillaries.

Function -

The exchange of oxygen and carbon dioxide takes place between the blood of the capillaries that surround the alveoli and the gases present in the alveoli. Alveoli are the site of gaseous exchange.

Nephrons are the basic filtration unit. They filter the blood to remove harmful toxins of of the blood and forms urine.