NCERT Solutions for Class 10 Science Chapter 6 Life Processes

NCERT Intext Questions

 Page Number 95

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

Ans. In multicellular organisms like humans, all the body cells are not in direct contact with the surrounding environment. Therefore, every cell of the body will not get oxygen as per need only by the process of diffusion from the environment. Also, diffusion is too slow to cover the distance between the gas exchange surface and the site where oxygen is required. Therefore diffusion is insufficient to meet the oxygen requirements of multicellular organisms.

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

Ans. The main criteria used to decide whether something is alive are breathing and respiration. However, living beings also show growth and movement.

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

Ans. The raw materials used by an organism depend on the mode of nutrition of the organism. Generally, these are organic compounds and small inorganic molecules. Autotrophic organisms such as plants and some algae use CO2, H2O and sunlight to prepare their food whereas hetrotrophic organisms such as animals and fungi use food, O2, H2O to obtain energy.

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

Ans. Processes essential for maintaining life are nutrition, respiration, excretion, metabolism, reproduction etc.

 Page Number 101

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

Ans.

Autotrophic nutrition Heterotrophic nutrition
1. In this mode of nutrition an organism makes or synthesizes its own food. In this mode of nutrition an organism cannot make or synthesize its own food.
2. Organisms use simple inorganic materials like carbon dioxide and water and synthesise their food in presence of sunlight. Organisms cannot make their own food from simple inorganic matter and depend on other organisms for their food.
3. All green plants and some algae undergo this mode of nutrition. All the animals, most bacteria and fungi undergo this mode of nutrition.

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

Ans. The following are the raw materials required for photosynthesis:

  1. Carbon dioxide: Plants get carbon dioxide from the environment/atmosphere through stomata.
  2. Water: Plants absorb water from the soil through roots and transport to leaves.
  3. Sunlight: Plants get sunlight from the sun.
  4. Chlorophy ll: It is present in chloroplast found in green leaves and green parts of plants.

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

Ans. Role of acid in our stomach is:

  1. To make acidic medium which is necessary for the activation of the enzyme pepsin.
  2. To kill bacteria which the food may contain.

4. What is the function of digestive enzymes ?

Ans. The main function of digestive enzyme is to target a specific nutrient, breakdown it to simpler form so it can be absorbed by the walls of intestine. Different types of enzymes target different types of nutrients. For example: Amylase breaks down starch, protease breaks down proteins and lipase breaks down lipids.

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

Ans. The small intestine is designed to provide maximum area for absorption of digested food and its transfer into the blood for its circulation into the body. For this the inner lining of the small intestine has numerous finger-like projections called villi. The villi are richly supplied with blood vessels which take the absorbed food to each and every cell of the body. 

 Page Number 105

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

Ans. Aquatic organisms use oxygen which is dissolved in surrounding water. Since air dissolved in water has fairly low concentration of oxygen, the aquatic organisms have much faster rate of breathing.
Terrestrial organisms take oxygen from the oxygen-rich atmosphere through respiratory organs. Hence, they have much less breathing rate than aquatic organisms.

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

Ans. There are two ways to oxidise glucose to obtain energy, i.e., aerobic respiration and anaerobic respiration.

1. Aerobic respiration: In presence of oxygen glucose breaksdown to pyruvate through glycolysis and finally to H2O and CO2 to obtain energy.

$$\text{Glucose + Oxygen} \xrightarrow[]{} \text{Carbon dioxide + Water + Energy}$$

2. Anaerobic respiration: In absence of oxygen glucose breaks down to pyruvate through glycolysis and then to either ethanol in yeast or lactic acid in muscle to obtain energy.

$$\text{Glucose}\xrightarrow[]{\text{Yeast}}\text{Ethanol + Carbon dioxide + Energy}\\\text{Glucose}\xrightarrow[]{\text{Muscle}}\text{Latic acid + Energy}$$

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

Ans. During breating, gases such as oxygen and carbon dioxide are inhaled, bind with oxygen to form oxyhaemoglobin. Through circulation of blood oxygen is supplied to all tissue. The dissolved CO2 is transported from tissues to lung through blood then this CO2 is exhaled out in the environment.

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

Ans. Within the lungs, the air passage divides into smaller and smaller tubes, called bronchi which in turn form bronchioles. The bronchioles terminate in balloon-like structures, called alveoli. The walls of alveoli are supplied with an extensive network of blood vessels. Thus lungs maximise the area for gaseous exchange through the presence of large number of alveoli which are richly supplied with blood. 

 Page Number 110

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

Ans. The transport system (circulatory system) in human beings mainly consists of heart, blood and blood vessels.

  1. Function of heart: The heart receives deoxygenated blood from the various body parts and pumps it to lungs for enriching with oxygen. It receives purified blood from lungs and pumps it around the body.
  2. Function of blood: Blood transports oxygen, carbon dioxide, digested food, hormones and nitrogeneous waste like urea. It also protects the body from diseases and regulates the body temperature.
  3. Function of blood vessels: The blood pushed by the heart flows through the blood vessels (arteries, veins and capillaries) and also comes back to the heart through them.

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

Ans. Separation of oxygenated and deoxygenated blood allows good supply of oxygen to the body. As mammals and birds require a higher supply of oxygen to get energy to keep their body warm at different climate.

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

Ans. Xylem and phloem are the two main components of the plant transport system in highly organized plants. Xylem conducts water and minerals obtained from soil to the rest of the plant where as phloem transports food materials from the leaves to different parts of plant.

4. How are water and minerals transported in plants?

Ans. Water and minerals are transported in plants by the xylem. The root hairs present at the top of roots absorb the water and minerals from soil by the process called diffusion. The water and minerals absorbed by the root hair pass from cell to cell by osmosis through epidermis, root cortex, endodermis and reach the root xylem.
The pressure at the top of xylem vessels is lower whereas the pressure at the bottom remains high. Due to this, the water and minerals flow up the xylem vessels into leaves.

5. How is food transported in plants?

Ans. Phloem transports food materials from leaves to different parts of plant. The transportation of food loaded in phloem tubes is achieved by utilizing energy from ATP which helps in creating osmotic pressure that transports food from higher concentration to lower concentration.

 Page Number 112

1. Describe the structure and functioning of nephrons.

Ans. Structure of nephrons: The main components of the nephron are glomerules, Bowman’s capsule and a long renal tubule.

  1. Bowman’s capsule: This is a cup like structure from which the renal tubule extents. Ultrafiltration takes place here.
  2. Glomerules: These are small tufts of capillaries through which blood flows in high pressure.
  3. Renal tubules: In these reabsorption of water takes place.
Life Processesans1pg112

Functions of nephron:

  1. Filteration: Filtration of blood takes place in Bowman’s capsule from the capillaries of glomerulus. The filtrate passes into the tubular part of the nephron. This filtrate contains glucose, amino acids, urea, uric acid, salts and water.
  2. Reabsorption: As the filtrate 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.
  3. Urine: The filtrate which is remained after reabsorption is called urine. Urine contains dissolved nitrogenous wastes like urea and uric acid, excess salts and water. Urine is collected from nephrons to carry it to the ureter from where it passes into urinary bladder.

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

Ans. Plants get rid of waste products in following ways:

  1. Gaseous wastes like CO2 and O2 are expelled from the stomata.
  2. Water from the leaves through transpiration.
  3. Solid wastes, through shedding of leaves, peeling of bark, falling of fruits.
  4. Gums and Resins are excreted from the lenticels in the bark.

3. How is the amount of urine produced regulated?

Ans. The amount of urine is regulated by kidney. It depends on the quantity of excess water and wastes dissolved in water.

  1. Quantity of water: When water is abundant in the body tissues, large quantities of dilute urine is excreted out. When water is less in quantity in the body tissues, small quantity of concentrate urine is excreted.
  2. Quantity of dissolved wastes: Dissolved wastes, especially nitrogenous wastes, like urea and uric acid and salts are excreted from the body. When there is more quantity of dissolved wastes in the body, more quantity of water is required to excrete them. Therefore, the amount of urine produced increases.
  3. Hormones:  The amount of urine produced is also regulated by certain hormones which control the movement of water and Na+ ions in and out of the nephrons.

NCERT Exercise Questions

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

  • (i) Nutrition
  • (ii) Respiration
  • (iii) Excretion
  • (iv) Transportation

Ans. (iii) Excretion

Explanation: The kidneys in human beings are a part of the system for excretion. Kidneys are the main excretory organs of human. They filter blood and excrete urea.

2. The xylem in plants are responsible for:

  • (i) Transport of water
  • (ii) Transport of food
  • (iii) Transport of amino acids
  • (iv) Transport of oxygen

Ans. (i) Transport of water

Explanation: Xylem in plants is responsible for transport of water and minerals from soil to different parts of plant body.

3. The autotrophic mode of nutrition requires:

  • (i) Carbon dioxide and water
  • (ii) Chlorophyll
  • (iii) Sunlight
  • (iv) All of the above
  • Ans. (iv) All of the above

Explanation: The raw materials for autotrophic nutrition required are carbon dioxide, water, chlorophyll to prepare the food in the presence of sunlight.

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

  • (i) Cytoplasm
  • (ii) Mitochondria
  • (iii) Chloroplast
  • (iv) Nucleus
  • Ans. (ii) Mitochondria
  • Explanation: In aerobic respiration pyruvate break down into CO2 and H2O. Thus produce high energy in the form of ATP. It takes place in mitochondria.

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

Ans. Digestion of fats takes place in the small intestine.

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

Lipase enzyme present in the pancreatic juice causes break down 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.

$$\text{Fats}\xrightarrow[\text{by bile salts}]{\text{emulsified}}\text{Emulsified fats}\xrightarrow[\text{lipase}]{\text{pancreatic juice}}\text{Break down of fats}\xrightarrow[\text{juice lipase}]{\text{intestinal}}\text{Fatty Acids + Glycerol}$$

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

Ans. Saliva contains salivary amylase enzyme that breaks down starch into sugars like maltose.

$$\underset{\text{(complex molecule)}}{\text{Starch + Salivary amylase}}\xrightarrow{}\underset{\text{(simple molecule)}}{\text{Starch + Salivary amylase}}$$

Saliva keeps the mouth cavity clean and moistens the food that helps in chewing and breaking down the big pieces of food into smaller ones.

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

Ans. Carbon dioxide, water, chlorophyll and sunlight are the necessary conditions required for the autotrophic nutrition.

Food (starch) and oxygen are the byproducts of autotrophic nutrition.

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

Aerobic respiration Anaerobic respiration
1. It takes place in the presence of oxygen. It takes place in the absence of oxygen.
2. Complete breakdown of glucose takes place. Partial breakdown of glucose takes place.
3. The end products are always carbon dioxide and water. The end products are ethanol and carbon dioxide (as in yeast) and lactic acid (as in animal muscles).
4. More energy is produced per molecule of glucose broken down. Less energy is produced per molecule of glucose broken down.
5. Takes place in cytoplasm and mitochondria. Takes place only in cytoplasm.

Some organisms which use anaerobic respiration are yeast, bacteria etc.

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

Ans. The alveoli are designed to maximise the exchange of gases in following ways:

  1. 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.
  2. Alveoli have balloon-like structure. Hence, provide maximum surface for exchange of gases.

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

Ans. Haemoglobin is a respiratory pigment that transports oxygen to the body cells. Therefore, deficiency of haemoglobin would lead to a shortage of oxygen in the cells of the body and it can also develop a disease called anaemia.

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

Ans. In our heart blood enters twice and is also pumped out twice from the heart. The deoxygenated blood from all the body parts is brought to the right atrium through vena cava from where it is sent to right ventricle. From right ventricle, the blood is pumped to the lungs for oxygenation through pulmonary artery. The oxygenated blood from lungs again enters the left atrium of the heart through pulmonary veins. From left atrium it is sent to left ventricle, from where this oxygenated blood is pumped to different parts of body through the arteries. In this way the blood flows through the heart twice, that’s why it is called ‘double circulation’.
Necessity of double circulation: Double circulation helps to separate oxygenated and deoxygenated blood from mixing with each other. Such separation allows a high supply of oxygen to body, which is useful for the maintenance of body temperature.

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

Ans.

Xylem Phloem
1. Xylem transports water and dissolved minerals from roots to aerial parts of the plant. Phloem transports prepared food material from leaves to other parts of plant in dissolved form.
2. In xylem, the transport of material takes place through vessels and tracheids which are dead tissues. In phloem, transport of material takes place through sieve tubes with the help of companion cells, which are living cells.
3. Transportation of material in xylem requires physical forces such as transpirational pull. Transportation of material in phloem requires energy in the form of ATP.
4. Movement of water is unidrectional i.e., upwards from the roots to the aerial parts of the plants. Movement of food is bidirectional i.e., both upward and downward.

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

Ans.

Alveoli Nephron
1. Alveoli are functional units of lungs. Nephrons are functional units of kidney.
2. A mature lung has about 30 crore alveoli. A kidney has about 10 lakh nephrons.
3. Alveoli provide a wide surface area for gaseous exchange. The surface area of a nephron is not much more.
4. The exchange of O2 and CO2 takes place through the network of capillaries in alveoli. The Bowman’s capsule in nephron regulates the concentration of water and salts.