NCERT Solutions for Class 10 Science Chapter 6 Life Processes

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Chapter 6 Life Processes Class 10 Science NCERT Solutions

In Text Questions

Page No: 95

1. Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?

Solution

Diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans because:

(i) The body design is very complex and the oxygen demand is quite high. The oxygen requirements of an animal cannot be met by the process of diffusion as it is a very slow process.

(ii) All the cells of the body are not in direct contact with the surrounding environment.

(iii) Intake of oxygen in multicellular organism takes place by one organ and used in another organ.

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

Solution

The movement of a body is the most important criterion to decide whether something is alive. A living organism can also have movements at molecular level which are not visible to the naked eyes. Therefore, living organisms perform certain life processes which include respiration, excretion, reproduction, growth etc., which enables it to sustain itself.

3. What are outside raw materials used for by an organism?

Solution

The raw materials required by an organism will vary depending on the complexity of the organism and its environment. An organism use various outside raw materials given below:

(i) Food to supply energy, materials like minerals, vitamins etc. for working and maintenance of cells/tissues.

(ii) Water to provide medium in the body to live and carry out all the metabolic reactions necessary for life.

(iii) Oxygen is used for respiration.

4. What processes would you consider essential for maintaining life?

Solution

Life processes like nutrition, respiration, transportation, excretion, locomotion, reproduction etc., are essential for maintaining life.

Page No: 101

1. What are the differences between autotrophic nutrition and heterotrophic nutrition?

Solution

Autotrophic Nutrition	Heterotrophic Nutrition
It is the nutrition in which organic food is manufactured from inorganic raw materials.	It is the nutrition in which organic food is obtained from various sources.
It is a type of nutrition in which organism synthesise their own food by converting simple inorganic substances into complex organic substances.	It is a type of nutrition in which an organism can not synthesise their own food but obtain its nutrition or food from the autotrophs directly or indirectly.
Food is generally prepared during day time.	Food can be obtained at all time.
Inorganic substances constitute the raw materials for synthesis of food.	Inorganic substances are not much required.
Chlorophyll is present for trapping light energy.	Chlorophyll is absent.
Organisms performing autotrophic nutrition function as producers.	Organisms performing heterotrophic nutrition function as consumers.
All green plants and some bacteria have this type of nutrition.	All animals and fungi have this type of nutrition.

2. Where do plants get each of the raw materials required for photosynthesis?

Solution

Photosynthesis requires carbon dioxide, sunlight, water and chlorophyll as its basic raw materials for photosynthesis.

• Carbon dioxide: Plants absorb carbon dioxide present in the atmosphere through small pores called stomata on the surface of their leaves.

• Water: It is absorbed by the roots transported through the stem to leaves by a special structures called as xylem tissues.

• Sunlight: It is absorbed by the chlorophyll and other green parts of the plants.

3. What is the role of the acid in our stomach?

Solution

The role of the acid in our stomach:

• It creates acidic medium by which inactive enzyme pepsinogen is converted to active pepsin, which is a protein digesting enzyme. 

• It give signals to pancreas for producing digestive juices and enzymes to further breakdown food.

• It gets mixed with food and kills bacteria present in food.

4. What is the function of digestive enzymes?

Solution

Digestive enzymes such as amylase, lipase, pepsin, trypsin, etc. break down the complex food molecules like carbohydrates, proteins and fats into such small particles which can be absorbed from the alimentary canal into the blood stream.

5. How is the small intestine designed to absorb digested food?

Solution

The inner surface of small intestine has millions of tiny, finger-like projections called villi. The presence of villi gives the inner walls of the small intestine a very large surface area. And the large inner surface area of small intestine helps in the rapid absorption of the digested food.

Page No: 105

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

Solution

Terrestrial organisms take up oxygen from the atmosphere whereas aquatic animals obtain oxygen from water. The amount of oxygen dissolved in water is, however, limited. The terrestrial organisms take oxygen from air which contains much higher amount of oxygen. Thus, a terrestrial organism has an advantage over an aquatic organism in regard to obtaining oxygen because it is surrounded by an oxygen rich air and do not need adaptations for gaseous exchange.

2. What are the different ways in which glucose is oxidized to provide energy in various organisms?

Solution

Glucose is the nutrient of food which provides energy on decomposition. At first glucose (6 carbon molecules) is broken in the cytoplasm of cells of all organisms. This process yields a 3 carbon molecule compound called pyruvate.

• Anaerobic Respiration: This process takes place in absence of oxygen, e.g. in yeast during fermentation. In this case, pyruvate is converted into ethanol and carbon dioxide.

• Aerobic Respiration: In aerobic respiration, the breakdown of pyruvate takes place in presence of oxygen to give rise to 3 molecules of carbon dioxide and water. The release of energy in aerobic respiration is much more than anaerobic respiration.

• Lack of Oxygen: Sometimes, when there is lack of oxygen, especially during vigorous activity, in our muscles, pyruvate is converted into lactic acid (3 carbon molecule compounds). Formation of lactic acid in muscles causes cramp.

3. How is oxygen and carbon dioxide transported in human beings?

Solution

• Transport of Oxygen: Oxygen is carried from the lungs by the respiratory pigment haemoglobin which is present in red blood corpuscles.

• Transport of carbon dioxide: Carbon dioxide is more soluble in water than oxygen. So, most of the carbon dioxide produced during respiration in the human body is transported in the dissolved form in our blood.

4. How are the lungs designed in human beings to maximize the area for exchange of gases?

Solution

There are millions of alveoli in the lungs. The presence of millions of alveoli in the lungs provides a very large area for the exchange of gases. By lifting our ribs and flatten the diaphragm, the chest cavity becomes spacious. Air is sucked into the lungs and alveoli. The oxygen from the breath, diffuses into the blood and CO₂ from the blood brought from the body, diffuses out into the air.

Page No: 110

1. What are the components of the transport system in human beings? What are the functions of these components?

Solution

The main components of the transport system in human beings are the heart, blood, and blood vessels.

• Heart: Heart pumps oxygenated blood throughout the body. It collects deoxygenerated blood from various body parts and pumps oxygenated blood.

• Blood : It supply nutrients and oxygen to all the living cells and taking away waste products as well as carbon dioxide away from them.

• The blood vessels (arteries, veins, and capillaries) carry blood either away from the heart to various organs or from various organs back to the heart.

2. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?

Solution

As both birds and mammals are warm-blooded animals so they maintain their constant body temperature by cooling themselves when they are in a hotter environment and by warming their bodies when they are in a cooler environment. Hence, these animals require more oxygen for more cellular respiration so that they can produce more energy to maintain their body temperature. Thus, it is necessary for them to separate oxygenated and de-oxygenated blood, so that their circulatory system is more efficient and can maintain their constant body temperature.

3. What are the components of the transport system in highly organised plants?

Solution

The highly organised plants have the following components of transport system:

• Xylem: It consists of vessels and tracheids. Xylem helps to conduct water and minerals from soil to the leaves.

• Phloem: It consists of sieve tubes and companion cell. Phloem helps to transport food materials from leaves to various parts of the plant including roots.

4. How are water and minerals transported in plants?

Solution

The water and minerals are transported by xylem tissue in the plants. Xylem vessels and tracheids form a continuous system of water conducting channels reaching all parts of the plant. The process of transpiration also plays an important role in transport of water and minerals in the plants.

• Transport of water and minerals by root pressure: The xylem tissue is present in stems, roots, leaves of the plant. The root cells that are in close contact with the soil actively uptake ions, which create a difference between in the concentration of soil and roots cells, due to this difference water and minerals moves into the root cells and transported in various parts of the plant.

• Transport of water and minerals by transpiration: There is a continuous loss of water through stomata in the form of water vapour, this process is known as transpiration. Transpiration creates a suction which helps in absorption and upward movement of water and minerals from roots to leaves of the plant.

5. How is food transported in plants?

Solution

The transport of food from the leaves to the other parts of the plant occurs through the vascular tissue called phloem. The food (sugar) made in leaves is loaded into the sieve tubes of phloem tissue by using the energy derived from ATP. As a result, the osmotic pressure in the tissue increases, causing the water to move into it. This high pressure produced in the phloem, moves the food to all the parts of the plant that have less pressure in their tissues. This process is helpful in moving the food materials according to the needs of the plant.

Page No: 112

1. Describe the structure and functioning of nephrons.

Solution

Nephrons are the basic filtering units of kidneys. It has a cup-shaped bag at its upper end which is called Bowman's capsule. The lower end of Bowman's capsule is tube-shaped and it is called a tubule. The Bowman's capsule and the tubule taken together make a nephron. Each kidney possesses large number of nephrons, approximately 1-1.5 million.

Functioning of nephrons:

• The blood enters the kidney through the renal artery, which branches into many capillaries associated with glomerulus.

• As the blood flows along the tubule, useful substances such as glucose, amino acids, salts and water are selectively reabsorbed into the blood by capillaries surrounding the nephron tubule.

• The filtrate which remains after reabsorption is called urine. Urine is collected from nephrons by the collecting duct to carry it to the ureter.

2. What are the methods used by plants to get rid of excretory products?

Solution

• During photosynthesis, oxygen is produced as a by-product which is passed out from the plant body through stomata.

• The plants take in excess amount of water from the soil which is released through transpiration.

• Some waste products such as resins and gums are stored, especially in non-functional old xylem.

• Some waste products such as tannins, resins, gums are stored in bark, thereby removed as peeled off.

• Plants excrete some waste products through roots into the soil around them.

3. How is the amount of urine produced regulated?

Solution

The amount of urine produced is regulated by reabsorption of water and some of the dissolved substances into the blood through blood capillaries surrounding the tubules of nephrons. The amount of urine produced depends on how much excess water is present in the body and how much of dissolved wastes are to be excreted.

Page No: 113

Exercises

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

(b) respiration.

(c) excretion.

(d) transportation.

► (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.
► (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.
► (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.
► (b) mitochondria.

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

Solution

Fats are present in the form of large globules in the small intestine. are digested in the small intestine in our body. The liver secretes an alkaline liquid called bile into small intestine. The salts present in bile emulsify or break large globules of fat present in our food into smaller globules making it easy for the enzymes to act on them and digest them.  This is referred to as emulsification of fats. Pancreas secretes pancreatic juice into small intestine that breaks down the emulsified fat further. Finally, the enzymes present in intestinal juice brings about the complete digestion of fats by converting them into fatty acids and glycerol.

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

Solution

The role of saliva in the digestion of food:

• It 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?

Solution

The necessary conditions for autotrophic nutrition:

• Presence of chlorophyll in the living cells.

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

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

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

Carbohydrates (food) and O2 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.

Solution

Aerobic respiration	Anaerobic respiration
Takes place in the presence of oxygen.	Takes place in the absence of oxygen.
Complete breakdown of food occur.	Partial breakdown of food occur.
It always releases CO2 and H2O.	End products vary.
It occurs in cytoplasm and mitochondria.	It occurs only in cytoplasm.

Anaerobic mode of respiration is used by certain microorganisms such as yeast and some bacteria known as anaerobic bacteria.

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

Solution

The presence of millions of alveoli in the lungs provides a very large area for the exchange of gases. By lifting our ribs and flatten the diaphragm, the chest cavity becomes spacious. Air is sucked into the lungs and alveoli. The oxygen from the breath, diffuses into the blood and CO₂ from the blood brought from the body, diffuses out into the air.

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

Solution

The oxygen required for breathing and respiration is carried by haemoglobin present in our blood. The deficiency of haemoglobin in the blood of a person reduces the oxygen-carrying capacity of blood resulting in breathing problems, tiredness and lack of energy. The person looks pale and loses weight.

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

Solution

Double circulation is a process in which blood flows twice through the heart.

• The blood from all body parts is brought to the right auricle which pumps it into the right ventricle. From right ventricle blood is pumped to the lungs( for pulmonary artery) for oxygenation.

• The oxygenated blood from the lungs is

brought to the left auricle which pumps it left ventricle. From the left ventricle, oxygenated blood then distributed to all body parts through larger artery called Aorta.

Double circulation is necessary in human being to separate oxygenated and deoxygenated blood because this makes their circulatory system more efficient and helps in maintaining constant body temperature.

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

Solution

Xylem	Phloem
Xylem tissue helps in the transport of water and minerals.	Phloem tissue helps in the transport of food.
It carries the water and dissolved minerals only upwards from the roots of the plant.	Food is transported in both upward and downward directions.
Transport in xylem occurs with the help of simple physical forces such as transpiration pull.	Transport 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.

Solution

Alveoli	Nephrons
Structure	Structure
Alveoli are tiny balloon-like structures present inside the lungs.	Nephrons are tubular structures present inside the kidneys.
The walls of the alveoli are one cell thick and it contains an extensive network of blood capillaries.	Nephrons are made of glomerulus, bowman’s capsule, and a long renal tube.
Function	Function
Alveoli are the site of gaseous exchange.	Nephrons are the basic filtration unit.
The exchange of O2 and CO2 takes place between the blood of the capillaries that surround the alveoli and the gases present in the alveoli.	The blood enters the kidneys through the renal artery. The blood is entered here and the nitrogenous waste in the form of urine is collected by collecting duct.

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