NCERT Solutions For Class 10 Biology: Life Process

Intext Questions (Page 81)

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

Answer-
In multi-cellular organisms, the body design becomes more complex, and all the cells may not be in direct contact with the surrounding environment. If the body size of the organism increases, the distance over which oxygen needs to travel from the outside surface to the interior cells is large. Thus, simple diffusion will not meet the requirements of all the cells because it is a very slow process.

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

Answer-
We generally think of some sort of movement as common evidence for being alive. This movement may be growth-related or not (like a dog running or a cow chewing cud). Even when visible movement is absent (e.g., when asleep), breathing provides evidence. Crucially, movements over very small scales, specifically movements of molecules, are considered necessary for life by professional biologists.

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

Answer-
Outside raw materials are used by an organism for several critical purposes:

1. They serve as the source of energy (food) to perform maintenance functions and prevent damage and break-down of ordered structures.
2. Additional raw material is needed for the body size of the organism to grow and develop.
3. Materials from outside are needed to synthesise protein and other substances required in the body.

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

Answer-
The processes which together perform the maintenance job necessary to prevent damage and break-down in living organisms are called life processes. The processes essential for maintaining life include:

1. Nutrition (transferring a source of energy/food from outside to the inside).
2. Respiration (acquiring oxygen to break down food for energy).
3. Transportation (carrying food and oxygen to all parts of the body).
4. Excretion (removal and discarding of harmful waste by-products).

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Intext Questions (Page 87)

Question 1: What are the differences between autotrophic nutrition and heterotrophic nutrition?

Answer-

Feature	Autotrophic Nutrition	Heterotrophic Nutrition
Source of Food	Organisms use simple food material obtained from inorganic sources like carbon dioxide and water.	Organisms utilise complex substances prepared by other organisms.
Process	Involves photosynthesis, where substances are converted into stored forms of energy using sunlight and chlorophyll.	Involves breaking down complex substances into simpler ones using bio-catalysts called enzymes.
Organisms	Green plants and some bacteria.	Animals and fungi; their survival depends directly or indirectly on autotrophs.

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

Answer-
The raw materials required for photosynthesis are carbon dioxide, water, and other minerals:

1. Carbon dioxide ($\text{CO}_2$): Plants obtain carbon dioxide from the atmosphere through stomata, which are tiny pores present on the surface of the leaves.
2. Water: Water is taken up from the soil by the roots in terrestrial plants.
3. Nitrogen, Phosphorus, Iron, and Magnesium: These other necessary raw materials are taken up from the soil by the roots. Nitrogen is taken up in the form of inorganic nitrates or nitrites, or as organic compounds prepared by bacteria.

Question 3: What is the role of the acid in our stomach?

Answer-
The gastric glands in the wall of the stomach release hydrochloric acid ($\text{HCl}$). The role of this acid is:

1. To create an acidic medium in the stomach.
2. This acidic medium facilitates the action of the protein digesting enzyme called pepsin.
3. The acid also serves another, implied function related to killing bacteria in the food.

Question 4: What is the function of digestive enzymes?

Answer-
Enzymes are biological catalysts used by organisms. Their function is to facilitate the break-down of complex substances into smaller molecules so that the food can be absorbed from the alimentary canal. Examples include salivary amylase (breaking down starch into simple sugar) and trypsin and lipase in pancreatic juice.

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

Answer-
The small intestine is the main site for the absorption of digested food. It is designed for maximum absorption in two ways:

1. Length and Coiling: It is the longest part of the alimentary canal and is fitted into a compact space because of extensive coiling, maximizing the overall length and time for absorption.
2. Villi: The inner lining of the small intestine has numerous finger-like projections called villi. These villi increase the surface area for absorption. The villi are richly supplied with blood vessels that take the absorbed food to every cell of the body.

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Intext Questions (Page 89)

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

Answer-
A terrestrial organism has a significant advantage because it breathes oxygen from the atmosphere. The amount of oxygen in the air is fairly high compared to the amount of dissolved oxygen in water. Due to this, terrestrial organisms do not need to process large volumes of medium (air) compared to aquatic organisms (water), whose rate of breathing is much faster to compensate for the low dissolved oxygen.

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

Answer-
In all cases, the first step is the break-down of glucose (a six-carbon molecule) into pyruvate (a three-carbon molecule). This process takes place in the cytoplasm. The pyruvate is then broken down further by different pathways:

1. Aerobic Respiration (Presence of Oxygen): Takes place in the mitochondria. Pyruvate is broken down completely to give three molecules of carbon dioxide and water. This process releases a lot greater amount of energy.
2. Anaerobic Respiration (Absence of Oxygen): Takes place in the cytoplasm.
   a. In yeast (during fermentation), pyruvate is converted into ethanol and carbon dioxide.
   b. In muscle cells (due to lack of oxygen during sudden activity), pyruvate is converted into lactic acid (a three-carbon molecule), which causes cramps.

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

Answer-
Transportation of gases in human beings is handled by the blood:

1. Oxygen Transport: Oxygen is taken up from the air in the lungs by respiratory pigments and carried to tissues. In human beings, the respiratory pigment is haemoglobin, which has a very high affinity for oxygen and is present in the red blood corpuscles.
2. Carbon Dioxide Transport: Carbon dioxide is more soluble in water than oxygen is. Hence, it is mostly transported in the dissolved form in our blood (plasma).

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

Answer-
The lungs are designed to maximize the surface area for gas exchange through the structure of the alveoli (singular—alveolus).

1. The air passage divides into smaller and smaller tubes which finally terminate in balloon-like structures called alveoli.
2. The alveoli provide a vast surface where the exchange of gases can take place.
3. The walls of the alveoli are very fine and delicate and contain an extensive network of blood-vessels.
4. If the alveolar surface were spread out, it would cover about $\text{80 m}^2$, highlighting the large efficient surface available for exchange.

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Intext Questions (Page 96)

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

Answer-
The transport (circulatory) system in human beings consists of three main components: the heart, blood, and blood vessels.

1. Heart: A muscular pumping organ (as big as a fist) that pushes blood around the body. It has different chambers to prevent the mixing of oxygen-rich blood and carbon dioxide-rich blood, ensuring a highly efficient supply of oxygen.
2. Blood: A fluid connective tissue that consists of plasma and suspended cells. It transports food, oxygen, carbon dioxide, nitrogenous wastes, and other substances like salts. Oxygen is carried by red blood corpuscles (containing haemoglobin).
3. Blood Vessels: A network of tubes to reach all the tissues. They include arteries (carrying blood away from the heart under high pressure), veins (collecting blood back to the heart), and capillaries (smallest vessels with one-cell thick walls where material exchange occurs).

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

Answer-
The separation of the right side (de-oxygenated blood) and the left side (oxygenated blood) of the heart is necessary because mammals and birds have high energy needs. They constantly use energy to maintain their body temperature. The separation allows a highly efficient supply of oxygen to the body, which is essential to meet their substantial energy requirements derived from aerobic respiration.

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

Answer-
In highly organised plants, a proper transportation system is essential due to the large distances involved in transport. The components are constructed as independently organised conducting tubes known collectively as vascular tissue.

1. Xylem: Moves water and minerals obtained from the soil, generally in an upward direction.
2. Phloem: Transports products of photosynthesis (food) from the leaves (where they are synthesised) to other parts of the plant, in both upward and downward directions.

Question 4: How are water and minerals transported in plants?

Answer-
Water and minerals are transported in plants by the xylem tissue. This transport involves two main mechanisms:

1. Root Pressure: Cells in the roots actively take up ions from the soil, creating a concentration difference. Water moves into the root xylem from the soil to eliminate this difference, creating a column of water that is steadily pushed upwards. Root pressure is more important at night.
2. Transpiration Pull: During the day, the evaporation of water molecules from the cells of the leaf (transpiration) creates a suction. This suction pulls water from the xylem cells of roots all the way up to the leaves, forming the major driving force for water movement.

Question 5: How is food transported in plants?

Answer-
The transport of soluble products of photosynthesis (food) is called translocation, and it occurs in the phloem.

1. Location: Translocation takes place in the sieve tubes with the help of adjacent companion cells, moving material in both upward and downward directions.
2. Mechanism (Energy Use): Unlike water transport, translocation in phloem is achieved by utilising energy from ATP. Material like sucrose is transferred into the phloem tissue, which increases the osmotic pressure of the tissue.
3. Movement: This pressure causes water to move into the phloem, which in turn moves the material to tissues that have less pressure (e.g., storage organs like roots, fruits, seeds, or growing buds).

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Intext Questions (Page 99)

Question 1: Describe the structure and functioning of nephrons.

Answer-
Structure of Nephrons:
The nephron is the basic filtration unit in the kidneys. Each kidney has large numbers of nephrons packed close together. Each nephron has two main structural parts:

1. A cluster of very thin-walled blood capillaries (like in the lungs).
2. A cup-shaped end of a coiled tube called Bowman’s capsule which is associated with the capillary cluster and collects the filtrate.

Functioning of Nephrons (Urine Production):
The purpose of making urine is to filter out waste products from the blood, specifically nitrogenous waste such as urea or uric acid.

1. Filtration: Blood enters the capillary cluster, and initial filtration takes place. The initial filtrate contains waste products as well as useful substances like glucose, amino acids, salts, and a major amount of water.
2. Selective Re-absorption: As the urine flows along the coiled tube, these useful substances are selectively re-absorbed back into the blood. The amount of water re-absorbed depends on how much excess water is in the body and the amount of dissolved waste to be excreted.
3. Collection: The urine forming in each kidney eventually enters the ureter, which connects the kidney to the urinary bladder where it is stored until released through the urethra.

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

Answer-
Plants use varied and often completely different strategies for excretion than animals:

1. Gaseous Wastes: Plants deal with gaseous wastes like oxygen (from photosynthesis) and $\text{CO}_2$ (from respiration) by diffusion.
2. Water: Plants get rid of excess water by the process of transpiration.
3. Stored Wastes: Many waste products are stored in cellular vacuoles.
4. Shedding: Waste products may be stored in leaves that fall off.
5. Gums and Resins: Other waste products are stored as resins and gums, especially in old xylem.
6. Excretion into Soil: Plants also excrete some waste substances into the soil around them.

Question 3: How is the amount of urine produced regulated?

Answer-
The amount of urine produced is regulated primarily by the selective re-absorption of water that occurs as the initial filtrate flows along the coiled kidney tubules (nephrons).
The amount of water re-absorbed depends on two factors:

1. How much excess water there is in the body.
2. How much of dissolved waste there is to be excreted.
   Normally, the initial filtrate is about 180 L daily, but only a litre or two is actually excreted because the remaining water is re-absorbed.

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Exercise Questions (Page 99-100)

Question 1: The kidneys in human beings are a part of the system for
(a) nutrition. (c) excretion.
(b) respiration. (d) transportation.

Answer-
The kidneys in human beings are the main organs for the biological process involved in the removal of harmful metabolic wastes, which is called excretion.
The correct option is (c) excretion.

Question 2: The xylem in plants are responsible for
(a) transport of water. (c) transport of amino acids.
(b) transport of food. (d) transport of oxygen.

Answer-
The xylem is one of the independently organised conducting tubes in plants. The function of xylem is to move water and minerals obtained from the soil.
The correct option is (a) transport of water.

Question 3: The autotrophic mode of nutrition requires
(a) carbon dioxide and water. (c) sunlight.
(b) chlorophyll. (d) all of the above.

Answer-
Autotrophic nutrition is fulfilled by photosynthesis, which converts carbon dioxide and water into carbohydrates in the presence of sunlight and chlorophyll.
The correct option is (d) all of the above.

Question 4: The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
(a) cytoplasm. (c) chloroplast.
(b) mitochondria. (d) nucleus.

Answer-
The break-down of pyruvate using oxygen is called aerobic respiration. This process takes place in the mitochondria and breaks up the three-carbon pyruvate molecule to give three molecules of carbon dioxide and water.
The correct option is (b) mitochondria.

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

Answer-
Fats are primarily digested in the small intestine, which is the site of complete digestion. The process involves two steps:

1. Emulsification: Fats are present in the intestine as large globules. Bile salts (from the liver) break them down into smaller globules. This increases the efficiency of enzyme action, similar to the emulsifying action of soaps.
2. Enzyme Action: The pancreas secretes pancreatic juice containing the enzyme lipase. Lipase acts on the emulsified fats, finally breaking them down into fatty acids and glycerol. Enzymes present in the intestinal juice also aid in this conversion.

Question 6: What is the role of saliva in the digestion of food?

Answer-
Saliva is a fluid secreted by the salivary glands when food is ingested. Its roles are:

1. Wetting: It wets the food to make its passage smooth along the soft lining of the digestive tract.
2. Enzymatic Action: Saliva contains an enzyme called salivary amylase. This enzyme breaks down starch, which is a complex molecule, to give simple sugar. The food is mixed thoroughly with saliva by the muscular tongue while chewing.

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

Answer-
Autotrophic nutrition is fulfilled by the process of photosynthesis.
Necessary Conditions:
The conversion of carbon dioxide and water into carbohydrates requires:

1. Presence of chlorophyll (in chloroplasts).
2. Presence of sunlight (light energy).
3. Intake of carbon dioxide from the atmosphere.
4. Uptake of water from the soil.

By-products:
The main by-product of photosynthesis is oxygen. Water is also produced. The main energy product, carbohydrates, are stored as starch.

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

Answer-

Feature	Aerobic Respiration	Anaerobic Respiration
Oxygen Requirement	Takes place in the presence of air (oxygen).	Takes place in the absence of air (oxygen).
Site	Occurs in the mitochondria.	Occurs in the cytoplasm.
Products	Pyruvate is broken down completely to carbon dioxide, water, and energy.	Products are ethanol and $\text{CO}_2$ (in yeast) or lactic acid (in muscle cells).
Energy Release	The release of energy is a lot greater.	Releases comparatively less energy.

Organisms using Anaerobic Respiration:

1. Yeast (during fermentation).
2. Muscle cells (in humans, during a temporary lack of oxygen).

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

Answer-
The alveoli are the terminal structures of the respiratory passage within the lungs. Their design maximizes gas exchange:

1. Structure: They are balloon-like structures providing a vast surface area.
2. Surface Area: The extensive folding means the alveolar surface, if spread out, would cover about $\text{80 m}^2$. This vast area ensures efficient exchange of gases.
3. Blood Supply: The walls of the alveoli contain an extensive network of blood-vessels. This rich blood supply ensures that oxygen can be quickly absorbed by the blood and $\text{CO}_2$ can be efficiently released from the blood into the alveolar air.
4. Residual Volume: The lungs always contain a residual volume of air during the breathing cycle, providing sufficient time for oxygen to be absorbed and for the carbon dioxide to be released.

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

Answer-
Haemoglobin is the respiratory pigment present in the red blood corpuscles that has a very high affinity for oxygen.
A deficiency of haemoglobin would mean the body's capacity to transport oxygen efficiently would be drastically reduced. Since oxygen is required for aerobic respiration to release energy (ATP), a deficiency of haemoglobin would lead to insufficient oxygen delivery to the cells and tissues. This results in a condition where the individual feels fatigued or lacks the energy needed for normal activities. If diffusion were the only method of oxygen delivery, it would take years to reach the extremities.

Question 11: Describe double circulation of blood in human beings. Why is it necessary?

Answer-
Description of Double Circulation:
In human beings and other vertebrates, the blood goes through the heart twice during each complete cycle of passage through the body; this is known as double circulation.

1. Pulmonary Circulation: The de-oxygenated blood from the body enters the right atrium, is pumped to the right ventricle, and then pumped to the lungs for oxygenation.
2. Systemic Circulation: The oxygen-rich blood returns from the lungs to the left atrium, is transferred to the muscular left ventricle, and is finally pumped out to the rest of the body.

Necessity of Double Circulation:
Double circulation is necessary because the separation of the right side and the left side of the heart is useful to keep oxygenated and de-oxygenated blood from mixing. This separation allows a highly efficient supply of oxygen to the body. This efficiency is crucial for organisms like mammals and birds that have high energy needs and constantly use energy to maintain their body temperature.

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

Answer-

Feature	Xylem Transport	Phloem Transport
Material Transported	Primarily transports water and minerals.	Transports products of photosynthesis (food), amino acids, and other substances.
Direction of Flow	Materials are generally moved in a unidirectional (upward) flow from roots to leaves.	Materials are moved in both upward and downward directions (according to the plant’s needs).
Driving Force	Largely explained by simple physical forces, primarily transpiration pull during the day and root pressure at night.	Achieved by utilising energy from ATP (an active process).
Mechanism	Water moves passively due to pressure differences and suction.	Sucrose is transferred into phloem using ATP, which increases osmotic pressure, causing water movement.

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

Answer-
Both alveoli and nephrons utilize a structure with a large surface area and extensive blood supply to perform filtering/exchange functions for the body.

Structure Comparison:

1. Alveoli: They are balloon-like structures that provide a surface for gas exchange. Their walls contain an extensive network of blood-vessels.
2. Nephrons: The basic filtration unit involves a cluster of very thin-walled blood capillaries associated with a cup-shaped Bowman’s capsule. The long, coiled tube structure further facilitates its function.

Functioning Comparison:

1. Purpose:
   • Alveoli: To facilitate the exchange of gases—absorbing oxygen into the blood and releasing $\text{CO}_2$ from the blood.
   • Nephrons: To filter out nitrogenous waste products (like urea) from the blood to form urine.
2. Filtration/Exchange:
   • Alveoli: Exchange is based on diffusion across the thin walls.
   • Nephrons: Filtration occurs initially at the capsule. Unlike the alveoli, where exchange is simple, nephrons perform selective re-absorption of useful materials (glucose, water, salts) after initial filtration, which is a key part of their function and is absent in the artificial kidney process (hemodialysis).
3. Transport: Both rely on the circulatory system: the alveoli pass oxygen to the blood, while the nephrons filter waste from the blood.