NCERT Solutions - Class 10 Science Chapter 5: Life Processes

Answer - Diffusion is a slow process and works efficiently only in small distances. In multicellular organisms like humans, body size and complexity are high, so oxygen cannot reach deep cells quickly through diffusion alone. Hence, a specialized respiratory system is needed to transport oxygen efficiently to all cells.

Answer - The main criterion to decide if something is alive is whether it shows movement, either visible or at the cellular level. Also, living things perform vital life processes like respiration, nutrition, growth, reproduction, and response to stimuli.

Answer - Outside raw materials like food, water, and oxygen are used by organisms for producing energy, growth, repair, and maintaining bodily functions. For example, plants take in carbon dioxide and water to prepare food by photosynthesis.

Answer - The essential life processes include nutrition, respiration, transportation, and excretion. These processes help in providing energy, removing waste, and maintaining a stable internal environment necessary for survival.

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Answer - Plants obtain the raw materials for photosynthesis as follows:

• Carbon dioxide (CO₂) from the air through stomata.
• Water (H₂O) from the soil through roots.
• Sunlight from the sun absorbed by chlorophyll in leaves.

Answer - The hydrochloric acid in our stomach serves two main functions:

• It creates an acidic medium that activates the enzyme pepsin, which helps digest proteins.
• It kills bacteria and harmful microbes present in the food.

Answer - Digestive enzymes break down complex food molecules into simpler forms that can be easily absorbed by the body.
For example:
• Amylase breaks down starch into sugar.
• Pepsin breaks down proteins into peptides.
• Lipase breaks down fats into fatty acids and glycerol.

Answer - The inner lining of the small intestine has finger-like projections called villi, which increase the surface area for absorption.

• Villi contain a network of blood capillaries to transport absorbed nutrients.
• The large surface area and rich blood supply make absorption efficient and quick.

Answer - Terrestrial organisms breathe in oxygen from the air, which has a higher concentration of oxygen compared to water. This makes the process of respiration more efficient in land organisms.

Aquatic organisms extract dissolved oxygen from water, which is available in lower amounts, making the process slower and less efficient.

Answer - Glucose is oxidised in two major ways depending on the availability of oxygen:

1. Aerobic Respiration:
• Occurs in presence of oxygen.
• Glucose (C₆H₁₂O₆) is completely broken down into carbon dioxide and water.
• Large amount of energy is released.

2. Anaerobic Respiration:
• Occurs in absence of oxygen.
• In yeast, glucose is broken down into ethanol and carbon dioxide.
• In muscles, glucose is broken down into lactic acid.
• Less energy is released compared to aerobic respiration.

Answer - • Oxygen is transported by red blood cells. It binds with haemoglobin to form oxyhaemoglobin and is carried to different parts of the body.

• Carbon dioxide is mostly transported in dissolved form in the blood plasma. A small amount also binds with haemoglobin to form carbaminohaemoglobin.

Answer - • The lungs contain millions of tiny air sacs called alveoli, which increase the surface area for gas exchange.

• Each alveolus is surrounded by a network of blood capillaries.

• The walls of alveoli are very thin and moist, which allows easy diffusion of gases.

This structural design ensures maximum surface area and efficient exchange of oxygen and carbon dioxide.

Answer - The transport system in human beings mainly consists of the heart, blood, and blood vessels.

a. Heart – Acts as a pump to circulate blood throughout the body.
b. Blood – Carries oxygen, carbon dioxide, nutrients, and waste materials.
c. Blood vessels – These include arteries, veins, and capillaries, which help transport blood to and from different parts of the body.

Answer - Mammals and birds are warm-blooded animals that require a constant and high energy supply. Separating oxygenated and deoxygenated blood ensures efficient oxygen delivery to body tissues, improving the rate of respiration and maintaining body temperature. It prevents the mixing of pure and impure blood, allowing better oxygen supply.

Answer - In highly organised plants, the transport system includes two types of tissues:

a. Xylem – Transports water and minerals from the roots to other parts of the plant.
b. Phloem – Transports food produced in the leaves to all parts of the plant.

Answer - Water and minerals are transported through the xylem tissue. The roots absorb water and minerals from the soil, which are then pulled upward through the stem due to transpiration pull, root pressure, and capillary action, reaching all parts of the plant.

Answer - Food is transported in plants through phloem tissue. This process is called translocation. The food prepared in the leaves during photosynthesis is moved to other parts of the plant using energy in the form of ATP. This movement can occur in both upward and downward directions.

Answer - Structure of Nephron:
The nephron is the structural and functional unit of the kidney. Each nephron consists of the following parts:

a. Bowman's capsule – A cup-shaped structure containing a bundle of capillaries called the glomerulus.
b. Proximal convoluted tubule (PCT) – The twisted tube close to Bowman's capsule.
c. Loop of Henle – A U-shaped tube that extends into the medulla.
d. Distal convoluted tubule (DCT) – A twisted tube that continues from the loop of Henle.
e. Collecting duct – The part where urine from many nephrons is collected.

Functioning:
1. Filtration: Blood is filtered in the glomerulus, and the filtrate enters Bowman's capsule.
2. Reabsorption: Useful substances like glucose, amino acids, and water are reabsorbed in the tubules.
3. Secretion: Waste substances are secreted into the tubule from the surrounding capillaries.
4. Urine formation: The remaining fluid becomes urine, which flows into the collecting duct.

Answer - Plants use the following methods to remove waste materials:

a. Gaseous wastes like oxygen and carbon dioxide are released through stomata and lenticels.
b. Storage in vacuoles – Some wastes are stored in cell vacuoles, especially in old or dead cells.
c. Excretion through leaves – Wastes stored in leaves are removed when the leaves fall.
d. Secretion into surrounding soil – Roots sometimes release harmful substances into the soil.
e. Formation of gums and resins – Wastes like gums and resins are stored in old xylem tissues and get dried up.

Answer - The amount of urine produced is regulated by several factors:

a. Water intake: More water intake leads to increased urine formation.
b. ADH (Antidiuretic Hormone): This hormone controls the reabsorption of water in the kidneys. If the body needs to conserve water, more ADH is released, reducing urine volume.
c. Salt concentration: High salt levels in the blood cause more water reabsorption, decreasing urine output.
d. Body temperature and activity: Excess sweating during physical activity or heat reduces the amount of urine to conserve water.

Answer - The correct answer is: (c) excretion.

Answer - The correct answer is: (a) transport of water.

Answer - The correct answer is: (d) all of the above.

Answer - The correct answer is: (b) mitochondria.

Answer - Fats are digested in the small intestine. The liver secretes bile juice, which emulsifies fats by breaking them into smaller droplets. This increases the surface area for the enzyme lipase (secreted by the pancreas) to act and convert fats into fatty acids and glycerol.

Answer - Saliva contains an enzyme called salivary amylase (ptyalin), which breaks down starch into simpler sugars. It also moistens the food, making it easier to chew and swallow.

Answer - The necessary conditions for autotrophic nutrition are:
a. Presence of chlorophyll
b. Availability of sunlight
c. Carbon dioxide
d. Water

By-products of autotrophic nutrition (photosynthesis) are glucose and oxygen.

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Answer - Alveoli are tiny balloon-like air sacs in the lungs that have:
a. A large surface area
b. Thin walls (one cell thick)
c. Rich blood supply via capillaries
These features help in efficient diffusion of oxygen into blood and carbon dioxide out of it.

Answer - Haemoglobin carries oxygen in the blood. A deficiency leads to less oxygen being transported, causing fatigue, shortness of breath, and a condition known as anaemia.

Answer - Double circulation means blood passes through the heart twice in one complete cycle — once for oxygenation (pulmonary circulation) and once to deliver oxygen to body parts (systemic circulation).

Importance: It ensures separation of oxygenated and deoxygenated blood, allowing efficient oxygen delivery to tissues — vital for warm-blooded animals.

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