CBSE Science, Class X | Chapter 6, Life Processes | NCERT Textbook Exercise (Answers)

Class 10 Science, Chapter - 6, LIFE PROCESSES

NCERT (CBSE) Textbook Exercise Questions

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

(a) nutrition

(b) respiration

(c) excretion

(d) transpiration

Ans: (c)

Q.2: The xylem in plants is responsible for

(a) transport of water

(b) transport of food

(c) transport of amino acids

(d) transport of oxygen.

Ans: (a)

Q.3: The autotrophic mode of nutrition requires

(a) carbon dioxide and water

(b) chlorophyll

(c) sunlight

(d) all of the above. 

Ans: (d)

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

(a) cytoplasm

(b) mitochondria

(c) chloroplast

(d) nucleus.  

Ans: (b)

Q.5: How are fats digested in our body? Where does this process takes place?

Ans: Digestion of Fat:

Digestion of fat takes place in the small intestine. The fats are present in the form of large globules in the small intestine. Fat-digesting enzymes are not able to act upon large globules efficiently.

Bile juice secreted by the liver is poured into the intestine along with pancreatic juice. The bile salts present in the bile juice emulsify the large globules of fats. So, due to emulsification large globules breakdown into small globules, which provide larger surface area to act upon by the enzymes.

Lipase enzyme present in the pancreatic juice causes breakdown of emulsified fats. Glands present in the wall of small intestine secrete intestinal juice which contains lipase enzyme that converts fats into fatty acids and glycerol.      

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

Ans: Saliva is secreted by salivary glands.  It has important roles in the digestion of food:
(a) It moistens the food which help in chewing and breaking of the food particles into smaller ones, so that the  digestive enzyme salivary amylase can digest the starch efficiently.
(b) Saliva contains a digestive enzyme called salivary amylase, which breaks down starch into sugars like maltose.   

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

Ans: The following the necessary conditions for autotrophic nutrition:

1. Presence of chlorophyll in the living cells.

2. Provision of supply of water to green parts or cells of the plant either through roots or by surrounding environment.

3. Availability of sufficient sunlight to provide the energy required to carry out photosynthesis.

4. Sufficient supply of carbon dioxide which is one of the important components for the formation of carbohydrates during photosynthesis.

The by-products of autotrophic nutrition are starch (carbohydrate) and oxygen. 

Q.8: What are the differences between aerobic and anaerobic respirations? Name some organisms that use the anaerobic respirations.   

Ans: The differences between aerobic and anaerobic respirations:

Aerobic respirations

Anaerobic respirations

1. Aerobic respiration takes place in the presence free oxygen. 2. In Aerobic respiration complete oxidation of glucose takes place. 3. End products of Aerobic respiration are CO2, water and energy (686 kcal).   4. Large amount of energy is released, i.e. 36 ATP molecules per glucose molecule.   5. First step of Aerobic respiration (glycolysis) takes place in cytoplasm while the next step takes place in mitochondria. 6. It takes place in all higher organisms.

1. Anaerobic respiration takes place in the absence of free oxygen. 2. In Anaerobic respiration the glucose molecule is incompletely broken down. 3. End products of Anaerobic respiration are ethyl alcohol (or lactic acid), CO2, and a little energy (58 kcal).   4. Small amount of energy is released, i.e. 2 ATP molecules per glucose molecule. 5. Complete anaerobic respiration occurs in cytoplasm. 6. It takes place in lower organisms like yeast and muscles of man.

Organisms which use anaerobic respiration are yeasts, bacteria and parasites like tapeworm, Ascaris, etc.  

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

Ans: The alveoli are thin walled and richly supplied with a network of blood vessels to facilitate exchange of gases between blood and the air filled in alveoli. they have balloon - like structure that provide maximum surface area for exchange of gases.  

Q.10: What would be the consequences of deficiency of haemoglobin in our bodies?

Ans: In respiration, Haemoglobin helps in the transportation of oxygen to the body cells .  In case of deficiency of haemoglobin in blood, its oxygen carrying capacity decreases  resulting into a deficiency of oxygen in our body cells. Because of this the person suffers from breathlessness, an indication of anaemia.  

The average haemoglobin content of blood, irrespective of sex, is 14.5 gm per 100 mL.   

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

Ans: In human beings, the blood goes through the heart twice during each cycle i.e. the blood passes through the human heart two times to supply once to the whole body. So, it is called Double Circulation of blood.

The double circulation of blood includes:

(i) Systematic Circulation

(ii) Pulmonary Circulation

Systematic Circulation: It supplies oxygenated blood from left auricle to left ventricle, thereby pumped to various body parts. The deoxygenated blood is collected from the various body organs by the veins to pour into vena cava and finally into the right atrium (auricle). Right atrium transfers the blood into the right ventricle.

Pulmonary Circulation: The deoxygenated blood is pumped by the right ventricle into the lungs for oxygenation. The oxygenated blood is brought back to left atrium (auricle) of the human heart. From left atrium, the oxygenated blood is pushed into the left ventricle. The left ventricle pumps oxygenated blood into aorta for systematic circulation. 

Fig:- Schematic representation of blood circulation

[Source: NCERT Science Textbook for Class X, page 106] 

Necessity (Importance) of Double Circulation:

There is a partition between the right side and the left side of human heart which is particularly useful to prevent mixing of deoxygenated with oxygenated blood. This type of separation of deoxygenated and oxygenated blood ensures highly efficient supply of oxygen to the body. This is important in case of humans because it constantly gives energy to maintain their body temperature.

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

Ans: Xylem and Phloem are two types of vascular tissues for the transport of substances in plants. The differences in the transport of materials are summarized below:

Xylem

Phloem

1. Xylem conducts water and dissolved mineral from roots to leaves and other part. 2. In xylem, transport of material takes place through vessels and tracheids which are dead tissues. 3. In xylem, upward movement of water and dissolved materials is mainly achieved by transpiration pull. It is caused due to suction created by evaporation of water molecules from the stomata of a leaf.   4. Movement of water is achieved by simple physical forces. There is no expenditure of energy. So, ATP molecules are not required.

1. Phloem conducts prepared food material from leaves to other parts of plant in dissolved form. 2. In phloem, transport of material takes place through sieve tubes with the help of companion cells, which are living cells. 3. In translocation, material is transferred into phloem tissue using energy from ATP. This increases the osmotic pressure that moves the material in the phloem to the tissues which have less pressure. 4. The translocation in phloem is an active process and requires energy. This energy is taken from ATP.

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

Ans:

Comparison between Alveoli and Nephron

Alveoli

Nephron

1. Alveoli have thin walled balloon - like structure. Surface is fine and delicate. 2. Alveoli are supplied with extensive network of thin walled blood vessels, i.e. capillaries for exchange of gases. 3. Alveoli increase surface area for diffusion of CO2 from blood to air and O2 from air to blood. 4. Alveoli only provide surface for exchange of gases in the lungs. 5. Alveoli are very small and a large number of them are present in each lung.

1. Nephron have thin walled cup-shaped structure attached with thin walled tubule. 2. Bowman’s capsule is supplied with a cluster of capillaries called glomerulus for filtration. A network of blood vessel is present around the tubular part of nephron for re-absorption of useful substances and water.    3. Nephrons also increase surface area for filtration of blood and re-absorption of useful substances and water from filtrate leaving behind urine. 4. Tubular part of nephron also carries the urine to collecting duct.    5. A large number of nephrons, the basic filtration unit, are present in each kidney.

FURTHER STUDY on the Chapter 'Life Processes'

• Life Processes | Class 10, CBSE Biology | NCERT Science, Chapter 6, Textbook In-text Questions - Answers  
• Class 10 NCERT (CBSE) Science | Life Processes | Sample Questions - Study Material