NCERT Solutions Class 10 (Science) Chapter 6 (Life Process)

NCERT Solutions Class 10 Science 

The NCERT Solutions in English Language for Class 10 Science Chapter 6 (Life Process) have been provided here to help the students solve the questions from this exercise. 

Chapter – 6 (Life Process) 

Questions

1. Why is diffusion insufficient to meet the oxygen requirement of multicellular organisms like us ?
Answer – Multicellular organisms such as humans possess complex body designs. They have specialised cells and tissues for performing various necessary functions of the body such as intake of food and oxygen. Unlike unicellular organisms, multicellular cells are not in direct contact with the outside environment. Therefore, diffusion cannot meet their oxygen requirements.

2. What criteria do we use to decide whether something is alive ?
Answer – Any visible movement such as walking, breathing, or growing is generally used to decide whether something is alive or not. However, a living organism can also have movements, which are not visible to the naked eye. Therefore, the presence of life processes is a fundamental criterion that can be used to decide whether something is alive or not.

3. What are outside raw materials used by an organism ?
Answer – Food by heterotrophic organisms ; carbon dioxide, minerals, sunlight and water by autotrophic organisms ; oxygen by all aerobic organisms.

4. What processes would you consider essential for maintaining life ?
Answer – Life processes of nutrition, metabolism, respiration, exchange of materials, transportation, excretion and awareness.

Questions

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

2. Where does the plant get each of the raw materials for photosynthesis ?
Answer – Plants require the following raw material for photosynthesis:
1. Carbon Dioxide: At through stomata.
2. Water: Soil through roots.
3. Minerals: Soil through roots. ,

3. What is the role of acid in our stomach ? 
Answer – The hydrochloric acid (HCl) present in our stomach dissolves bits of food and creates an acidic medium. In this acidic medium, ezyme pepsinogen is converted to pepsin, which is a protein- digesting enzyme.

4. What is the junction of digestive enzymes ? 
Answer – Digestive enzymes such as amylase, lipase, pepsin, trypsin, etc. help in the breaking down of complex food particles into simple ones. These simple particles can be easily absorbed by the blood and thus transported to all the cells of the body.

5. How is small intestine designed to absorb digested food ?
Answer – The small intestine has small projections called microvilli, which increase the surface volume, making the absorption more effective. Within the villi, there are numerous blood vessels that absorb digested food and carry it to the bloodstream. Blood transports food to each part of our body.

Questions

1. What advantage does a terrestrial organism possess over aquatic organism with regard to obtaining oxygen for respiration ?
Answer – Air contains about 21% of oxygen while water haà less than 1% oxygen in dissolved state. A terrestrial organism is able to get several times more oxygen than an aquatic organism.

2. What are the different ways in which glucose is oxidised to provide energy in various organisms ?
Answer – Glucose is first broken down in the cell cytoplasm into a three carbon molecule called pyruvate. Pyruvate is further broken down by different ways to provide energy.
The breakdown of glucose by different pathways can be illustrated as follows.

In yeast and human muscle cells, the breakdown of pyruvate occurs in the absence of oxygen whereas in mitochondria, the breakdown of pyruvate occurs in the presence of oxygen.

3. How is oxygen and carbon dioxide transported in human beings ? 
Answer –
Oxygen:
1. 97% in combined state with haemoglobin called oxyhaemoglobin.
2. 3% dissolved in plasma.

Carbon Dioxide:
1. 5-7% as dissolved in plasma.
2. 70% as sodium bicarbonate in plasma.
3. 23% in combined state with haemoglobin called carbaminohaemoglobin.

4. How are lungs designed in human beings to maximise the area for exchange of gases ?
Answer – The exchange of gases takes place between the blood of the capillaries that surround the alveoli and the gases present in the alveoli. Thus, alveoli are the site for exchange of gases. The lungs get filled up with air during the process of inhalation as ribs are lifted up and diaphragm is flattened. The air that is rushed inside the lungs fills the numerous alveoli present in the lungs. lung contains 300-350 million alveoli. These numerous alveoli increase the surface area for gaseous exchange making the process of respiration more efficient.

Questions

1. What are the components of the transport system in human beings ? What are the junctions of these components ?
Answer – Human transport system has two components, blood vascular system and lymphatic system..
Blood Vascular System: It consists of blood, blood vessels (tubes) and heart.
Heart: It is pumping organ of blood vascular system.
Blood : Blood transports oxygen, nutrients, CO2, and nitrogenous wastes.
Blood vessels : Blood vessels, arteries and veins carry blood to all parts of the body.

2. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds ? 
Answer – Mammals and birds are warm blooded animals. They constantly use energy to maintain their body temperature. They have a higher energy need and require more oxygenated blood for their cells. It is important that their oxygenated blood does not mix up with deoxygenated blood.

3. What are the components of the transport system in highly organised plants ? 
Answer – Transport system of highly organised plants consists of xylem and phloem.
Xylem: It is used in transport of water and minerals. Xylem is made of tracheids, vessels, xylem fibres and xylem parenchyma. Tracheids and vessels constitute the tracheary elements or channels for transport of water and minerals.
Phloem: It is used for transport or translocation of organic solutes or food. Phloem consists of sieve tubes, companion cells, phloem fibres and phloem parenchyma. Sieve tubes constitute the channels for transport of food materials.

4. How are water and minerals transported in plants ?
Answer – In plants, water and minerals are transferred from the soil to the leaves by the xylem cells. Root cells obtain salts from the soil, this creates a difference in the concentration of soil and root salts, due to which there is a constant movement of water in the xylem. Due to transpiration, there is a continuous loss of water and there is suction, due to which the constant movement of water is maintained, thus water and minerals are transported.

5. How is food transported in plants ?
Answer – Phloem transports food materials from the leaves to different parts of the plant body. The transportation of food in phloem is achieved by utilizing energy from ATP. As a result of this, the osmotic pressure in the tissue increases causing water to move into it. This pressure moves the material in the phloem to the tissues which have less pressure. This is helpful in moving materials according to the needs of the plant. For example, the food material, such as sucrose, is transported into the phloem tissue using ATP energy.

Questions

1. Describe the structure and functions of nephron.
Answer – Nephrons are the basic filtering units of kidneys. Each kidney possesses large number of nephrons, approximately 1-1.5 million. The main components of the nephron are glomerulus, Bowman’s capsule, and a long renal tubule.
Functioning of a nephron:

• The blood enters the kidney through the renal artery, which branches into many capillaries associated with glomerulus.
• The water and solute are transferred to the nephron at Bowman’s capsule.
• In the proximal tubule, some substances such as amino acids, glucose, and salts are selectively reabsorbed and unwanted molecules are added in the urine.
  
• The filtrate then moves down into the loop of Henle, where more water is absorbed.
• From here, the filtrate moves upwards into the distal tubule and finally to the collecting duct. Collecting duct collects urine from many nephrons.
• The urine formed in each kidney enters a long tube called ureter. From ureter, it gets transported to the urinary bladder and then into the urethra.

2. What are the methods used by plants to get rid of excretory products ?
Answer – Plants can get rid of excess of water by transpiration. Waste materials may be stored in the cell vacuoles or as gum and resin, especially in old xylem. It is also stored in the leaves that later fall off.

3. How is the amount of urine produced regulated ?
Answer – The amount of urine produced depends on the amount of excess water and dissolved wastes present in the body. Some other factors such as habitat of an organism and hormone such as Antidiuretic hormone (ADH) also regulates the amount of urine produced.

Exercises

1. The kidneys in human beings are a part of the system for
(a) Nutrition
(b) Respiration
(c) Excretion
(d) Transportation.
Answer – (c) Excretion

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.
Answer – (a) Transport of water

3. The autotrophic mode of nutrition requires,
(a) Carbon dioxide and water
(b) Chlorophyll
(c) Sun light
(d) All of the above.
Answer – (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.
Answer – (b) Mitochondria

5. How are fats digested in our bodies Where does this process take place ? 
Answer – Fats are present in the form of large globules in the small intestine. The small intestine gets the secretions in the form of bile juice and pancreatic juice respectively from the liver and the pancreas. The bile salts (from the liver) break down the large fat globules into smaller globules so that the pancreatic enzymes can easily act on them. This is referred to as emulsification of fats. It takes place in the small intestine.

6. What is the role of saliva in the digestion of food ? 
Answer – Saliva is secreted by the salivary glands, located under the tongue. 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 ?
Answer – Autotrophic nutrition takes place through the process of photosynthesis. Carbon dioxide, water, chlorophyll pigment, and sunlight are the necessary conditions required for autotrophic nutrition. 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.
Answer – 

:

Anaerobic Organisms: Yeast (can also perform aerobic respiration), Lactobacillus (bacterium), Ascaris (Roundworm), Taenia (Tapeworm).

9. How are alveoli designed to maximise the exchange of gases ?
Answer – Alveoli are small pouches or sacs. About 300 million alveoli occur inside each lung. The whole surface of an alveolus functions as respiratory surface. As there are about 300 million alveoli in each lung, a very large area of respiratory surface becomes available (about 80 m²) for exchange of gases.

10. What would be the consequence of deficiency of haemoglobin in our body ?
Answer – Deficiency of haemoglobin is called anaemia. In anaemia the blood is unable to carry the amount of oxygen required by the body (hypoxia). Lesser energy will be available to the body. The person will feel weak, pale, lethargic and unable to perform vigorous exercise or physical work.

11. Describe double circulation in human beings. Why is it necessary ?
Answer – The human heart is divided into four chambers − the right atrium, the right ventricle, the left atrium, and the left ventricle.
Flow of blood in the heart:

• The heart has superior and inferior vena cava, which carries de-oxygenated blood from the upper and lower regions of the body respectively and supplies this de-oxygenated blood to the right atrium of the heart.

Flow of blood in the human heart

• The right atrium then contracts and passes the de-oxygenated blood to the right ventricle, through an auriculo-ventricular aperture.
• Then the right ventricle contracts and passes the de-oxygenated blood into the two pulmonary arteries, which pumps it to the lungs where the blood becomes oxygenated. From the lungs, the pulmonary veins transport the oxygenated blood to the left atrium of the heart.
• Then the left atrium contracts and through the auriculo-ventricular aperture, the oxygenated blood enters the left ventricle.
• The blood passes to aorta from the left ventricle. The aorta gives rise to many arteries that distribute the oxygenated blood to all the regions of the body.

Schematic diagram of blood circulation in humans

• Therefore, the blood goes twice through the heart. This is known as double circulation.

Importance of double circulation:

• The separation of oxygenated and de-oxygenated blood allows a more efficient supply of oxygen to the body cells. This efficient system of oxygen supply is very useful in warm-blooded animals such as human beings.

As we know, warm-blooded animals have to maintain a 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, they require more O₂ for more respiration so that they can produce more energy to maintain their body temperature. Thus, the circulatory system of humans is more efficient because of the double circulatory heart.

12. What are the differences between the transport of materials in xylem and phloem ? 
Answer – Differences in Transport of Materials in Xylem and Phloem 

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

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