CBSE NCERT Class 10th Science 

Life Processes NCERT Text Book Questions & Answers

Question: 1: Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?

Answers:- The size of the multicellular organisms is very large compare to unicellular organisms. Diffusion is a passive mode of transport of substances and can transfer gases up to a very small distance only. This will not be sufficient for multicellular organisms’ needs.

Question: 2. What criteria do we use to decide whether something is alive?

Answer:- The main criteria to check for life, is the sign of breathing and respiration. If there is no sign of breathing or respirations then the given organism is not alive.

Question: 3:- What are outside raw materials used for by an organism?

Answer: Minerals and water and gases are outside raw materials used by an organism.

Question: 4:- What processes would you consider essential for maintaining life?

Answer: Processes essential for maintaining life are as follows:
Nutrition
Respiration
Reproduction
Excretion
Locomotion or movement

Question: 5. What are the differences between autotrophic nutrition and heterotrophic nutrition?

Answer: Autotrophic nutrition means that the organism is preparing its own food and is not dependent on any other organism for food. Green plants are autotrophs.
Heterotrophic nutrition means that the organism does not prepare its own food and is dependent on other organisms for food. All organisms which are not among green plants are heterotrophic.

Question: 6. Where do plants get each of the raw materials required for photosynthesis?

Answer:

Question: 7. What is the role of the acid in our stomach?

Answer: The hydrochloric acid is found in our stomach. It helps in killing harmful germs which may have come along with food.

Question: 8. What is the function of digestive enzymes?

Answer: The function of digestive enzyme is to hasten the process of breaking up of complex molecules into simpler and absorbable molecules. This makes it easy for the body to absorb food.

Question: 9. How is the small intestine designed to absorb digested food?

Answer: In the small intestine the innermost layer is in the shape of finger like structures. These are known as villi. Several folds because of villi increase the absorbing surface of small intestine. The blood capillaries in villi absorb simpler molecules from food.

Question: 10. What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?

Answer: In the aquatic habitat the concentration of oxygen is good up to a certain depth only. Moreover, as oxygen is available as dissolved in water, so taking oxygen from there is not a very efficient method to that.
In terrestrial habitat oxygen is available in free form so it is easier to absorb by organisms. This is more efficient so terrestrial organisms can facilitate better utilization of food by way of respiration.

Question: 11. What are the different ways in which glucose is oxidised to provide energy in various organisms?

Answer: There are two types of respiration for oxidization of glucose.
(a) Aerobic respiration: This involves complete oxidation of glucose hence optimum output of energy is achieved. This happens in presence of oxygen.
(b) Anaerobic respiration: As the name suggests this happens in the absence of oxygen hence complete oxidation of glucose does not take place. Usually bacteria show anaerobic respiration. Even sometimes in our calf muscles anaerobic respiration takes place.

Question: 12. How is oxygen and carbon dioxide transported in human beings?

Answer: Oxygen and carbon dioxide are transported in human beings with a dedicated gas transportation system. This system is mainly composed of following parts:
Lungs: Lungs help in breathing in oxygen rich air and breathing out carbon dioxide rich air.
Heart: Heart pumps deoxygenated blood to lungs for oxygenation and pumps oxygenated blood to different organs of body.
Veins: Veins usually carry deoxygenated blood from different body parts to the heart. One exception is the pulmonary vein which carries oxygenated blood from lungs to heart.
Arteries: Arteries usually carry oxygenated blood from heart to different parts of the body. One exception is pulmonary artery which carries deoxygenated blood from heart to lungs.

Question: 13. How are the lungs designed in human beings to maximise the area for exchange of gases?

Answer: The bronchioles in lungs are finely branched and end up in air sacs. The structure of air sac increases the surface area inside lungs. This helps in making a larger area for exchange of gases.

Question: 14. What are the components of the transport system in human beings? What are the functions of these components?

Answer: The transport system is mainly comprised of following organs:
Heart: Heart is a pumping organ and pumps blood. As blood carries gases and food and waste product along with it so heart plays a major role in transportation.
Lungs: The main job of lungs is in facilitating transport of oxygen and carbon dioxide to and from the body respectively.
Liver: Food goes to liver after it is absorbed by small intestine. From liver the food is distributed to different parts of body. This system is also called as hepatic portal system.

Question: 15. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?

Answer: Mammals and birds are warm blooded animals. This means they can control their body temperature and don’t have to depend on environment for their body temperature regulation. Because of this birds and mammals require optimum oxidization of glucose which would be possible with good supply of oxygen. By developing four chambered heart they have made it possible to completely segregate the oxygenated and deoxygenated blood in their bodies which is their need because of their habit and habitat.

Question: 16. What are the components of the transport system in highly organized plants?

Answer: The plant transport system in highly organized plants contains following:
(a) Xylem: To transport water and minerals from roots to other parts.
(b) Phloem: To transport food from leaves to other parts.

Question: 17. How are water and minerals transported in plants?

Answer: Water and minerals are transported from roots. At the level of roots the root pressure helps in rise of water and minerals up to some height. After that there is complex mechanism at work. The transpiration taking place in leaves creates a suction effect which pulls up water in minerals to great heights.

Question: 18. How is food transported in plants?

Answer: Food is transported in plants through phloem. The transport in phloem is an active process and involves use of energy. The energy in the form of ATP created osmotic gradient which results in transportation of food through phloem.

Question: 19. Describe the structure and functioning of nephrons.

Answer: The nephron is the functioning unit of kidneys. Nephron consists of a capsule shaped structure called Bowman’s capsule. The filtration of blood takes place in Bowman’s capsule under very high pressure. After that waste product goes to a network of collecting tubules which finally meet in a common collecting duct. The collecting duct meet in ureter which carries urine to the urinary bladder.

Question: 20. What are the methods used by plants to get rid of excretory products?

Answer: Plants get rid of carbon dioxide and oxygen through diffusion. Old branches and leaves are shed off when they become useless. Plants release some waste products through roots also. Some waste products are deposited near bark as raisins or gums.

Question: 21. How is the amount of urine produced regulated?

Answer: The kidney has a mechanism to reabsorb water from the filtrate. This depends on how much water is left in the body and in the filtrate. The comparative concentration of water gives a signal to the brain which then takes the required corrective action of either reabsorbing water or releasing more water. Thus the amount of urine formation is regulated by kidneys.

Question: 22. The kidneys in human beings are a part of the system for

(a) nutrition.
(b) respiration.
(c) excretion.
(d) transportation.
Answer: (c)

Question: 23. 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)

Question: 24. The autotrophic mode of nutrition requires

(a) carbon dioxide and water.
(b) chlorophyll.
(c) sunlight.
(d) all of the above.
Answer: (d)

Question: 25. The breakdown of pyruvate to give carbon dioxide, water and energy takes place in

(a) cytoplasm.
(b) mitochondria.
(c) chloroplast.
(d) nucleus.
Answer: (b)

Question: 26. How are fats digested in our bodies? Where does this process take place?

Answer: 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.

Question: 27. What is the role of saliva in the digestion of food?

Answer: Saliva contains the enzyme amylase which breaks complex molecules into sugar.

Question: 28. What are the necessary conditions for autotrophic nutrition and what are its byproducts?

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

Question: 29. What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.

Answer: 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.

Question: 30. How are the alveoli designed to maximise the exchange of gases?

Answer: The wall of alveoli contains a fine network of blood capillaries. This ensures maximum exchange of gases.

Question: 31. What would be the consequences of a deficiency of haemoglobin in our bodies?

Answer: 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.

Question: 32. Describe double circulation in human beings. Why is it necessary?

Answer: 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.

Question: 33. What are the differences between the transport of materials in xylem and phloem?

Answer: 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.

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