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NCERT Class 10 Science Life Processes: Exercise Solutions

Step-by-step working for every question of End-of-chapter exercises in NCERT's Class 10 Science book, chapter “Life Processes”, written by Shishya. Each question is in our own short words; open the NCERT chapter for the exact wording and figures.

1. Exercises Q1

   The kidneys are part of the system for (a) nutrition (b) respiration (c) excretion (d) transportation.

   1. The kidneys are bean-shaped organs located in the abdomen.
   2. Their main function is to filter waste products from the blood.
   3. They remove excess water, urea, and other metabolic wastes to form urine.
   4. This process of removing waste is called excretion.
   5. Therefore, the kidneys are part of the excretory system.

   Answer: (c) excretion

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2. Exercises Q2

   Xylem is responsible for transport of (a) water (b) food (c) amino acids (d) oxygen.

   1. Xylem is a complex tissue in plants that consists of hollow, dead cells.
   2. The main function of xylem is to transport water and dissolved minerals from the roots to the rest of the plant.
   3. Phloem is the tissue responsible for the transport of food and amino acids.
   4. Oxygen is not the primary substance transported by xylem.

   Answer: (a) water

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3. Exercises Q3

   Autotrophic nutrition needs (a) carbon dioxide and water (b) chlorophyll (c) sunlight (d) all of these.

   1. Autotrophic organisms prepare their own food from simple inorganic substances.
   2. They require carbon dioxide and water as raw materials for the process.
   3. Chlorophyll is the pigment that captures energy for this process.
   4. Sunlight provides the energy needed to convert these materials into food.
   5. Therefore, all the listed components are essential for autotrophic nutrition.

   Answer: (d) all of these

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4. Exercises Q4

   Pyruvate breaks down to carbon dioxide, water and energy in the (a) cytoplasm (b) mitochondria (c) chloroplast (d) nucleus.

   1. Pyruvate is the end product of glycolysis, which occurs in the cytoplasm.
   2. The complete breakdown of pyruvate into carbon dioxide and water happens during aerobic respiration.
   3. Aerobic respiration takes place inside the mitochondria of the cell.
   4. This process releases energy in the form of ATP.

   Answer: (b) mitochondria

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5. Exercises Q5

   How are fats digested in our bodies, and where?

   1. Fats are not digested in the stomach because gastric juice lacks lipase.
   2. In the small intestine, bile from the liver emulsifies large fat globules into smaller droplets.
   3. This emulsification increases the surface area for enzyme action.
   4. Pancreatic lipase then breaks down the emulsified fats into fatty acids and glycerol.
   5. The digestion of fats occurs primarily in the small intestine.

   Answer: Fats are digested in the small intestine where bile emulsifies them and pancreatic lipase breaks them into fatty acids and glycerol.

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6. Exercises Q6

   What is the role of saliva in digestion?

   1. Saliva is a watery fluid secreted by the salivary glands in the mouth.
   2. It contains an enzyme called salivary amylase, also known as ptyalin.
   3. This enzyme breaks down complex starch molecules into simpler sugar called maltose.
   4. The process begins in the mouth and continues until the food reaches the stomach.
   5. Saliva also moistens the food to form a soft bolus, making it easier to swallow.

   Answer: Saliva moistens food for easy swallowing and contains the enzyme salivary amylase which converts starch into maltose.

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7. Exercises Q7

   What conditions does autotrophic nutrition need, and what are its by-products?

   1. Autotrophic nutrition requires carbon dioxide, water, sunlight, and chlorophyll.
   2. These ingredients are used in the process of photosynthesis to make food.
   3. The main by-product released during this process is oxygen.
   4. The food made is glucose (stored as starch); oxygen is released as the by-product.

   Answer: Conditions: chlorophyll, sunlight, carbon dioxide and water. By-product: oxygen (the food made is glucose, stored as starch).

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8. Exercises Q8

   How do aerobic and anaerobic respiration differ? Name organisms that respire anaerobically.

   1. Aerobic respiration requires oxygen to break down glucose completely into carbon dioxide, water, and energy.
   2. Anaerobic respiration occurs in the absence of oxygen, breaking down glucose partially into substances like lactic acid or alcohol and carbon dioxide.
   3. Aerobic respiration releases a large amount of energy, while anaerobic respiration releases a small amount of energy.
   4. Aerobic respiration takes place in the mitochondria of cells, whereas anaerobic respiration takes place in the cytoplasm.
   5. Organisms that respire anaerobically include yeast, some bacteria, and muscle cells during intense exercise.

   Answer: Aerobic respiration needs oxygen and yields high energy; anaerobic respiration needs no oxygen and yields low energy; yeast and bacteria are anaerobic organisms.

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9. Exercises Q9

   How are the alveoli designed to maximise gas exchange?

   1. The lungs contain millions of tiny air sacs called alveoli, which provide a huge surface area for gas exchange.
   2. Each alveolus is surrounded by a dense network of capillaries, bringing blood very close to the air.
   3. The walls of the alveoli and capillaries are only one cell thick, allowing gases to diffuse easily.
   4. The thin walls and close proximity of blood vessels minimize the distance gases must travel.
   5. This design ensures that oxygen and carbon dioxide can be exchanged rapidly and efficiently.

   Answer: Alveoli maximize gas exchange through their large surface area, thin one-cell-thick walls, and close association with a dense network of capillaries.

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10. Exercises Q10

    What would a deficiency of haemoglobin do to us?

    1. Haemoglobin is the red pigment in red blood cells that binds with oxygen.
    2. It carries oxygen from the lungs to every part of the body.
    3. A deficiency of haemoglobin means the blood has a reduced capacity to carry oxygen.
       why?

       Oxidation is gain of oxygen (or loss of hydrogen); reduction is loss of oxygen (or gain of hydrogen). In a redox reaction one substance is oxidised while another is reduced.

    4. This leads to a condition called anaemia.
    5. Due to less oxygen supply, the body feels weak and tired.
    6. The heart has to work harder to pump enough oxygenated blood.

    Answer: A deficiency of haemoglobin causes anaemia, leading to weakness, fatigue, and shortness of breath due to reduced oxygen transport in the blood.

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11. Exercises Q11

    Describe double circulation of blood in humans. Why is it needed?

    1. Double circulation means the blood passes through the heart twice in one complete circuit around the body.
    2. In the first circuit, deoxygenated blood from the body enters the right atrium and is pumped to the lungs via the pulmonary artery.
    3. In the lungs, the blood releases carbon dioxide and picks up oxygen, becoming oxygenated.
    4. The oxygenated blood returns to the left atrium and is pumped by the left ventricle into the systemic circulation.
    5. This second circuit carries oxygen-rich blood to all body tissues via the aorta and returns deoxygenated blood to the heart.
    6. This separation is needed because it ensures that oxygenated and deoxygenated blood do not mix.
    7. Keeping the blood streams separate allows the heart to pump oxygen-rich blood to the body at a higher pressure.
    8. High pressure is essential to deliver sufficient oxygen to meet the high energy demands of the human body.

    Answer: Double circulation involves two circuits: pulmonary (heart to lungs) and systemic (heart to body). It is needed to separate oxygenated and deoxygenated blood, ensuring efficient oxygen delivery to meet high energy requirements.

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12. Exercises Q12

    How does transport in xylem differ from transport in phloem?

    1. Xylem transports water and dissolved minerals from the roots to the leaves.
    2. Phloem transports food (sugars) from the leaves to other parts of the plant.
    3. Xylem transport is unidirectional, moving only in one direction from roots to shoots.
    4. Phloem transport is bidirectional, moving food to both growing and storage parts.
    5. Xylem transport is driven by physical forces (root pressure and the transpiration pull from leaves) and uses no energy from ATP.
    6. Phloem transport is active and requires energy from ATP for loading and unloading.

    Answer: Xylem transports water and minerals unidirectionally via passive transport, while phloem transports food bidirectionally via active transport.

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13. Exercises Q13

    Compare alveoli in the lungs and nephrons in the kidneys in structure and functioning.

    1. Alveoli are tiny air sacs in the lungs where gas exchange occurs, while nephrons is the structural and functional unit of the kidney responsible for filtering blood.
    2. Structurally, alveoli are thin-walled, sac-like structures surrounded by a dense network of capillaries, whereas a nephron consists of a Bowman's capsule, a long coiled tubule, and associated blood capillaries.
    3. Functionally, alveoli facilitate the diffusion of oxygen into the blood and carbon dioxide out of the blood into the air.
    4. Nephrons function by filtering blood to remove waste products like urea and excess water, forming urine through processes like ultrafiltration, reabsorption, and secretion.
    5. Both structures have a large surface area and are highly vascularized to support their specific exchange or filtration roles efficiently.

    Answer: (i) Alveoli are gas exchange sacs in lungs; nephrons are filtration units in kidneys. (ii) Alveoli are thin-walled sacs with capillaries; nephrons have Bowman's capsule and tubules. (iii) Alveoli exchange O2 and CO2; nephrons filter blood to form urine.

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