NCERT Solutions For Class 10 Science Chapter 5 Life Processes: In this article, students can get comprehensive solutions for all the NCERT in-text and final exercise questions from CBSE Class 10 Science Chapter 5, Life Processes. All the NCERT solutions have been compiled into a PDF format, available for free download to students.
NCERT Solutions For Science Class 10 Chapter 5 Life Processes
Intext Solution- Page Number 81
1. Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?
Humans and other multicellular organisms have large bodies and require a lot of oxygen to reach all their cells quickly. Diffusion is a slow process and takes too long to transport oxygen throughout the body. To meet the oxygen demands of multicellular organisms, specialized transport systems like the circulatory system are necessary.
2. What criteria do we use to decide whether something is alive?
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 for by an organism?
Any organism uses organic molecules as raw material. Heterotrophs use food and autotrophs use carbon dioxide, minerals, water and all organisms use oxygen (for respiration) as raw materials.
4. What processes would you consider essential for maintaining life?
Processes essential for maintaining life are :
(i) Nutrition
(ii) Respiration
(iii) Transportation
(iv) Excretion
Intext Solution- Page Number 87
1. What are the differences between autotrophic nutrition and heterotrophic nutrition?
| S.No | Autotrophic Nutrition | Heterotrophic Nutrition |
| 1 | Organisms synthesize their food. | Organisms depend on other organisms for food. |
| 2 | Occurs in plants, algae, and some bacteria. | Occurs in animals, fungi, and most bacteria. |
| 3 | Requires energy from sunlight (photosynthesis) or chemicals (chemosynthesis). | No direct use of sunlight; depends on ready-made organic compounds. |
| 4 | Involves chlorophyll in photosynthesis (in plants). | No chlorophyll is involved. |
| 5 | CO₂ and water are used as raw materials. | Organic food (plants or other organisms) is used as a food source. |
2. Where do plants get each of the raw materials required for photosynthesis?
(i) Carbon dioxide: Plants get carbon dioxide from the environment/atmosphere through stomata.
(ii) Water: Plants absorb water from the soil through roots and transport it to leaves.
(iii) Sunlight: Plants get sunlight from the sun.
(iv) Chlorophyll: 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?
The role of acid in our stomach is :
(i)To kill bacteria that the food may contain.
(ii) To make an acidic medium which is necessary for the activation of the enzyme pepsin.
4. What is the function of digestive enzymes?
The food we eat is complex, i.e., it contains complex molecules. Digestive enzymes break down these complex molecules into smaller simpler molecules so that they can be absorbed by the walls of the intestine.
5. How is the small intestine designed to absorb digested food?
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 every cell of the body.
Intext Solution- Page Number 91
1. What advantage over an aquatic organism does a terrestrial organism have concerning obtaining oxygen for respiration?
Aquatic organisms use oxygen dissolved in the surrounding water. Since air dissolved in water has a fairly low concentration of oxygen, the aquatic organisms have a much faster rate of breathing.
Terrestrial organisms take oxygen from the oxygen-rich atmosphere through respiratory organs. Hence, they have a much lower breathing rate than aquatic organisms.
2. What are the different ways in which glucose is oxidised to provide energy in various organisms?
The first step of the breakdown of glucose (6 carbon molecules) takes place in the cytoplasm of cells of all organisms. This process yields a three-carbon molecule compound called pyruvate.
Further, the breakdown of pyruvate takes place in different ways in different organisms.
(i) Anaerobic respiration: The anaerobic respiration in plants (like yeast) produces ethanol and carbon dioxide as end products.
(ii) Aerobic respiration: In aerobic respiration breakdown of pyruvate takes place in the presence of oxygen to give rise to three molecules of carbon dioxide and water. The release of energy in aerobic respiration is much more than in anaerobic respiration.
(iii) Lack of oxygen: Sometimes, when there is a lack of oxygen, especially during physical exercise, in our muscles, pyruvate is converted into lactic acid (a 3-carbon molecule compound). The formation of lactic acid in muscles causes cramps.
3. How are oxygen and carbon dioxide transported in human beings?
(i) Transport of oxygen: Haemoglobin present in the blood takes up the oxygen from the air in the lungs. It carries the oxygen to tissues which are deficient in oxygen before releasing it.
(ii) Transport of carbon dioxide: Carbon dioxide is more soluble in water. Therefore, it is mostly transported from body tissues in the dissolved form in our blood plasma to the lungs. Here it diffuses from blood to air in the lungs.
4. How are the lungs designed in human beings to maximise the area for the exchange of gases?
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 alveoli present in the lungs provide a maximum surface for the exchange of gases. The alveoli have very thin walls and contain an extensive network of blood vessels to facilitate the exchange of gases.
Intext Questions Page Number- 96
1. What are the components of the transport system in human beings? What are the functions of these components?
The transport system (circulatory system) in human beings mainly consists of the heart, blood and blood vessels.
(i) Function of heart: The heart receives deoxygenated blood from the body parts and pumps it to the lungs for enrichment with oxygen. It receives purified blood from the lungs and pumps it around the body.
(ii) Function of blood: Blood transports oxygen, carbon dioxide, digested food, hormones and nitrogenous waste like urea. It also protects the body from diseases and regulates the body temperature.
(iii) 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?
Separation of oxygenated and deoxygenated blood allows good supply of oxygen to the body. This system is useful in animals that have high energy requirements. Mammals and birds constantly need oxygen to get energy to maintain their body temperature constant.
3. What are the components of the transport system in highly organised plants?
Xylem: This tissue transports water and minerals from the roots to other parts of the plant.
Phloem: This tissue transports food (sugars) from the leaves to other parts of the plant.
4. How are water and minerals transported in plants?
Water and minerals are transported in plants through the xylem tissue. Xylem cells have thick walls and are connected end-to-end to form long tubes. Water and minerals are absorbed from the soil by the plant's roots and are then transported upwards through these tubes to the leaves and other parts of the plant. This process is driven by a combination of capillary action, root pressure, and transpiration (the loss of water from leaves).
5. How is food transported in plants?
Food (sugars) is transported in plants through the phloem tissue. Phloem cells have sieve tubes with perforated end walls called sieve plates. Sugars produced in the leaves through photosynthesis are transported through these tubes to other parts of the plant, such as the roots and storage organs. This process is known as translocation and is driven by the difference in osmotic pressure between the source (leaves) and the sink (other parts of the plant).
Intext Solution- Page Number 98
1. Describe the structure and functioning of nephrons.
Nephrons are the functional units of the kidneys. Each kidney contains millions of nephrons. They are responsible for filtering waste products, excess water, and other unwanted substances from the blood.
Structure of a nephron:
Glomerulus: A network of capillaries that filters blood.
Bowman's capsule: A cup-shaped structure that surrounds the glomerulus and collects the filtered fluid.
Proximal convoluted tubule: A coiled tube that reabsorbs most of the filtered substances, including glucose, amino acids, and water.
Loop of Henle: A U-shaped loop that further concentrates the filtered fluid.
Distal convoluted tubule: A coiled tube that adjusts the final composition of the urine by reabsorbing or secreting specific ions.
Collecting duct: A tube that carries urine from the distal convoluted tubules to the renal pelvis and then to the ureter.
Functions of nephrons:
Filtration: The glomerulus filters blood, removing waste products and excess water.
Reabsorption: Most of the filtered substances are reabsorbed back into the bloodstream in the proximal convoluted tubule, loop of Henle, and distal convoluted tubule.
Secretion: Some substances, such as drugs and waste products, are secreted from the blood into the tubules to be excreted.
Concentration: The loop of Henle helps to concentrate the urine by reabsorbing water.
Regulation of blood volume and composition: The kidneys regulate blood volume and electrolyte balance by adjusting the amount of water and ions reabsorbed or secreted.
2. What are the methods used by plants to get rid of excretory products?
Plants primarily use two methods to get rid of excretory products:
Diffusion: Many plants secrete waste products, such as carbon dioxide and oxygen, directly into the air through their leaves. This process is known as diffusion.
Storage: Some plants store waste products, such as gums, resins, and latex, in specialized cells or tissues. These substances can later be excreted or remain in the plant as a protective mechanism.
3. How is the amount of urine produced regulated?
The amount of urine is regulated by the kidney. It depends on the quantity of excess water and wastes dissolved in water.
(i) Quantity of water: When water is abundant in the body tissues, large quantities of dilute urine are excreted out. When water is less in quantity in the body tissues, a small quantity of concentrated urine is excreted.
(ii) 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.
(iii) 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 Back Exercises Page Number- 99
1. The kidneys in human beings are a part of the system for
(a) nutrition (c) excretion
(b) respiration (d) transportation
Answer: Excretion
2. The xylem in plants is responsible for
(a) the transport of water and (c) the transport of amino acids.
(b) transport of food (d) transport of oxygen
Answer: the transport of water
3. The autotrophic mode of nutrition requires
(a) carbon dioxide and water. (c) sunlight.
(b) chlorophyll. (d) all of the above.
Answer: all of the above.
4. The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
(a) cytoplasm. (c) chloroplast.
(b) mitochondria. (d) nucleus
Answer: mitochondria
5. How are fats digested in our bodies? Where does this process take place?
Digestion of fats takes place in the small intestine. Bile juice secreted by the liver is poured into 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 a larger surface area to act upon the enzymes.
A lipase enzyme present in the pancreatic juice causes the breakdown of emulsified fats. Glands present in the wall of the small intestine secrete intestinal juice which contains lipase enzyme that converts fats into fatty acids and glycerol.
6. What is the role of saliva in the digestion of food?
Saliva plays several important roles in the digestion of food:
- Mechanical breakdown: Saliva helps to break down food into smaller pieces through a process called mastication.
- Chemical breakdown: Saliva contains the enzyme salivary amylase, which begins the breakdown of carbohydrates into simpler sugars.
- Lubrication: Saliva moistens food, making it easier to swallow.
- Protection: Saliva contains antimicrobial properties that help to protect against harmful bacteria.
7. What are the necessary conditions for autotrophic nutrition and what are its byproducts?
Necessary conditions for autotrophic nutrition :
(i) Presence of chlorophyll in the living cells.
(if) Provision of supply of water to green plants or cells of the plant.
(iii) Sufficient sunlight.
(iv) Sufficient supply of carbon dioxide.
A by-product of autotropic nutrition is oxygen.
8. What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.
| Feature | Aerobic Respiration | Anaerobic Respiration |
| Oxygen requirement | Requires oxygen | Does not require oxygen |
| Process | Complete breakdown of glucose into carbon dioxide and water | Incomplete breakdown of glucose into carbon dioxide and either ethyl alcohol or lactic acid |
| Energy production | Produces more energy | Produces less energy |
| Examples | Most organisms, including humans | Yeast, bacteria, muscle cells during intense exercise |
Organisms that use anaerobic respiration:
- Yeast: Yeast uses anaerobic respiration to produce alcohol and carbon dioxide in the process of fermentation.
- Bacteria: Many bacteria can survive and grow in anaerobic conditions, using anaerobic respiration to produce energy.
- Muscle cells: During intense exercise, when oxygen supply is limited, muscle cells can switch to anaerobic respiration to produce energy. This process results in the accumulation of lactic acid, which causes muscle fatigue.
9. How are the alveoli designed to maximise the exchange of gases?
(i) The alveoli are thin-walled and richly supplied with a network of blood vessels to facilitate the exchange of gases between blood and the air filled in alveoli.
(ii) Alveoli have balloon-like structures. Hence, provides a maximum surface for the exchange of gases.
10. What would be the consequences of a deficiency of haemoglobin in our bodies?
Due to the deficiency of haemoglobin in blood, its oxygen-carrying capacity decreases. As a result, the production of energy by oxidation will become slower. Therefore, one would fall sick and would feel fatigued most of the time.
11. Describe the double circulation of blood in human beings. Why is it necessary?
Double circulation in humans refers to the complete separation of oxygenated and deoxygenated blood during its journey through the heart and blood vessels. This system involves two distinct circuits:
Pulmonary circulation: Deoxygenated blood from the body is pumped by the right ventricle of the heart to the lungs for oxygenation. The oxygenated blood then returns to the left atrium of the heart.
Systemic circulation: Oxygenated blood from the left ventricle is pumped to the rest of the body to deliver oxygen and nutrients. Deoxygenated blood from the body tissues returns to the right atrium of the heart.
Double circulation is necessary for humans because:
Efficient oxygen delivery: It ensures that oxygenated blood is delivered to all tissues and organs, allowing for optimal cellular respiration and energy production.
Removal of waste products: It facilitates the removal of carbon dioxide and other waste products from the body tissues.
Maintenance of body temperature: It helps to regulate body temperature by distributing heat throughout the body.
Support for growth and development: It provides essential nutrients and oxygen for the growth and development of tissues and organs.
12. What are the differences between the transport of materials in the xylem and phloem?
| Feature | Xylem | Phloem |
| Substance transported | Water and minerals | Sugars (food) |
| Direction of transport | Upward (from roots to leaves) | Downward (from leaves to other parts) |
| Cells involved | Tracheids and vessel elements | Sieve tube elements and companion cells |
| Driving force | Transpiration, root pressure, capillary action | Osmotic pressure |
13. Compare the functioning of alveoli in the lungs and nephrons in the kidneys concerning their structure and functioning.
The double circulatory system of blood flow refers to the separate systems of pulmonary circulation and systemic circulation.
The adult human heart consists of two separate pumps, the right side with the right atrium and ventricle which pumps deoxygenated blood into the pulmonary circulation.
The oxygenated blood re-enters the left side of the heart through the pulmonary vein into the left atrium and passes to the left ventricle where it is pumped to the rest of the body. This part of the circulation is called systemic circulation. This type of circulation is called double circulation. The advantage of a double circulatory system is that blood can be pumped to the rest of the body at a higher pressure.
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