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Life Processes : NCERT Exercise Questions

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Q.1      The kidneys in human beings are a part of the system for
            (a) nutrition.                                    (b) respiration.
            (c) excretion.                                   (d) transportation.
Sol.      (c)

Q.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.
Sol.         (a)

Q.3       The autotrophic mode of nutrition requires
              (a) carbon dioxide and water.        (b) chlorophyll.
              (c) sunlight.                                     (d) all of the above.
Sol.        (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.
Sol.        (b)

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

Fats are present in the intestine in the form of large globules which makes it difficult for enzymes to act on them. Bile salts break them down into smaller globules increasing the efficiency of enzyme action. The pancreas secretes pancreatic juice which contains enzyme called lipase for breaking down emulsified fats. The walls of the small intestine contain glands which secrete intestinal juice. The enzymes present in it finally convert fats into fatty acids and glycerol.

Q.6       What is the role of saliva in the digestion of food?
Sol.        Saliva contains the enzyme amylase which breaks complex molecules into sugar.

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

Conditions necessary for photosynthesis:
Sunlight, carbon dioxide and chlorophyll.
Byproduct of photosynthesis: Oxygen

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

In aerobic respiration there is complete oxidation of glucose and the end product is water and carbon dioxide.
In anaerobic respiration there is incomplete oxidation of glucose and the end product is either lactic acid or alcohol.
Yeast and bacteria use anaerobic mode of respiration.

Q.9       How are the alveoli designed to maximise the exchange of gases?
Sol.       The wall of alveoli contains a fine network of blood capillaries. This ensures maximum exchange of gases.

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

Haemoglobin is the carrier of oxygen in blood. Deficiency of haemoglobin will lead to less supply of oxygen to different cells. This will, in turn lead inefficient utilization of food by the body. Finally person’s health will deteriorate.

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

In double circulation there is complete segregation of oxygenated and deoxygenated blood. Because of this the blood passes twice through the heart in one cycle of circulation hence the name double circulation.
This is necessary for optimum oxygen utilization as humans are warm blooded animals and need extra energy to maintain their body temperature.

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

Transport in xylem: The transport in xylem is from roots to upwards and takes place in only one direction. This is a kind of passive transport as no energy is required. Through xylem only water and minerals are transported.
Transport in phloem: The transport in phloem is bidirectional and food and some other products are transported. The transport in phloem is an active transport as it requires energy.

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

Alveoli Nephrons
Alveoli are sac like structure  Nephrons are a network of very fine tubules
Alveoli have network of blood capillaries on their walls Nephrons act like transit point for blood capillaries
Exchange of materials takes place through diffusion Exchange of materials takes place because of high pressure


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