Life Processes — Class 10 Science
Science · Chapter 5
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Chapter summary
Key ideas & terms
- Photosynthesis
- Process by which green plants make glucose using sunlight, CO₂ and water.
- Aerobic respiration
- Breakdown of glucose using oxygen, releasing more energy.
- Nephron
- The structural and functional filtering unit of the kidney.
- Xylem and phloem
- Plant tissues transporting water/minerals and food respectively.
Extra questions & answers
Why is the rate of breathing faster in aquatic organisms than in land animals?
Water has much less dissolved oxygen than air, so aquatic organisms must breathe faster to obtain enough.
Why is the human heart called a double pump?
Its right side pumps deoxygenated blood to the lungs and its left side pumps oxygenated blood to the body, keeping the two circuits separate.
What are life processes? Name them.
The basic functions performed by living organisms to stay alive: nutrition, respiration, transportation and excretion.
What is photosynthesis, and what are its raw materials?
The process by which green plants make food (glucose) using carbon dioxide and water in the presence of sunlight and chlorophyll, releasing oxygen.
How is the small intestine suited for absorption of food?
It is long and lined with finger-like villi that greatly increase the surface area and are rich in blood vessels for the rapid absorption of digested food.
Differentiate between aerobic and anaerobic respiration.
Aerobic respiration uses oxygen to break down glucose completely into CO₂ and water, releasing more energy; anaerobic respiration occurs without oxygen, giving products like lactic acid or alcohol and less energy.
Describe the human heart as a double pump.
Its right side receives and pumps deoxygenated blood to the lungs, while its left side receives oxygenated blood and pumps it to the body, keeping the two streams of blood separate (refer to the diagram of the heart in your NCERT textbook).
What is the role of xylem and phloem in plants?
Xylem transports water and dissolved minerals from the roots to the rest of the plant, while phloem transports the food made in the leaves to all other parts.
What is excretion, and what is the function of a nephron?
Excretion is the removal of harmful metabolic wastes from the body; the nephron is the filtering unit of the kidney that filters blood and forms urine.
How do plants get rid of their waste products?
Plants store some wastes in cells or as resins and gums, release oxygen and CO₂ through stomata, lose water by transpiration, and shed wastes when leaves, bark and fruits fall off.
QUESTIONS
1. Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
In multi-cellular organisms like humans, most cells are not directly exposed to the environment, and the distances between the body surface and internal cells are large. Diffusion is too slow to supply enough oxygen to all cells, so specialised respiratory and transport systems are required.
2. What criteria do we use to decide whether something is alive?
We decide whether something is alive by checking for life processes such as nutrition, respiration, transportation and excretion. Living organisms also show continuous molecular movements needed for the maintenance and repair of their organised structures.
3. What are outside raw materials used for by an organism?
An organism uses outside raw materials to obtain energy, grow, repair its body and maintain life. These materials include food, water and oxygen; plants also require carbon dioxide and mineral nutrients.
4. What processes would you consider essential for maintaining life?
The essential processes for maintaining life are nutrition, respiration, transportation of materials and excretion of metabolic wastes.
QUESTIONS
1. What are the differences between autotrophic nutrition and heterotrophic nutrition?
In autotrophic nutrition, organisms prepare their own food from simple inorganic substances such as carbon dioxide and water by using an external energy source, usually sunlight. In heterotrophic nutrition, organisms obtain ready-made organic food from other organisms and digest it into simpler substances.
2. Where do plants get each of the raw materials required for photosynthesis?
Plants obtain carbon dioxide from the air through stomata, water from the soil through their roots, and sunlight from the Sun. Chlorophyll required to absorb light energy is present in the chloroplasts of green cells.
3. What is the role of the acid in our stomach?
Hydrochloric acid creates the acidic medium required for pepsin to digest proteins. It also helps destroy many harmful microorganisms that may enter the stomach with food.
4. What is the function of digestive enzymes?
Digestive enzymes break complex and insoluble food substances into simpler, soluble molecules that can be absorbed through the intestinal wall and used by the body.
5. How is the small intestine designed to absorb digested food?
The small intestine is long and highly coiled, providing a large area for absorption. Its inner lining has numerous finger-like villi that further increase the surface area. Each villus has a thin wall and a rich supply of blood vessels, allowing digested nutrients to be absorbed and transported efficiently.
QUESTIONS
1. What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
Air contains much more oxygen than the amount dissolved in water. Therefore, terrestrial organisms can obtain oxygen more easily and need not breathe as rapidly as aquatic organisms.
2. What are the different ways in which glucose is oxidised to provide energy in various organisms?
Glucose is first broken down in the cytoplasm into pyruvate. In the presence of oxygen, pyruvate is completely broken down in mitochondria into carbon dioxide and water, releasing a large amount of energy. In yeast, without oxygen, it forms ethanol and carbon dioxide. In oxygen-deficient muscle cells, it forms lactic acid. The simplified pathways are:
3. How is oxygen and carbon dioxide transported in human beings?
Oxygen combines with haemoglobin in red blood corpuscles and is carried from the lungs to body tissues. Carbon dioxide is more soluble in water and is transported mainly in dissolved form in the blood plasma from the tissues to the lungs.
4. How are the lungs designed in human beings to maximise the area for exchange of gases?
Inside the lungs, the air passages divide repeatedly into smaller tubes ending in millions of balloon-like alveoli. These alveoli provide an enormous surface area. Their walls are thin, moist and surrounded by a dense network of capillaries, enabling rapid diffusion of oxygen and carbon dioxide.
QUESTIONS
1. What are the components of the transport system in human beings? What are the functions of these components?
The human transport system consists mainly of the heart, blood and blood vessels. The heart pumps blood throughout the body. Blood transports oxygen, carbon dioxide, digested food, hormones, salts and wastes. Arteries carry blood away from the heart, veins return blood to the heart, and capillaries allow the exchange of materials between blood and body cells. Platelets help clot blood, while lymph transports absorbed fats and returns excess tissue fluid to the blood.
2. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
Mammals and birds require a large and continuous supply of energy to maintain a constant body temperature. Complete separation prevents the mixing of oxygenated and deoxygenated blood and ensures that tissues receive blood with a high oxygen concentration, making respiration and energy release more efficient.
3. What are the components of the transport system in highly organised plants?
The transport system in highly organised plants consists of xylem and phloem. Xylem transports water and minerals from the roots, while phloem transports food and other soluble substances between different parts of the plant.
4. How are water and minerals transported in plants?
Root cells actively absorb mineral ions from the soil, causing water to enter the roots. Water and dissolved minerals move into the xylem, whose connected vessels and tracheids form continuous channels. Root pressure helps push water upward, while evaporation from leaves creates a transpiration pull that draws the water column from the roots to the aerial parts of the plant.
5. How is food transported in plants?
Food is transported through phloem by a process called translocation. Sugars such as sucrose are loaded into sieve tubes using energy from ATP. Water then enters the phloem by osmosis, creating pressure that moves food towards tissues where it is required or stored. Transport through phloem can occur in both upward and downward directions.
QUESTIONS
1. Describe the structure and functioning of nephrons.
A nephron is the structural and functional filtration unit of a kidney. It consists of a cluster of thin-walled blood capillaries called the glomerulus, enclosed by the cup-shaped Bowman's capsule, followed by a long coiled tubule that joins a collecting duct. Blood is filtered under pressure in the glomerulus, and the filtrate enters Bowman's capsule. As it passes through the tubule, useful substances such as glucose, amino acids, required salts and most water are selectively reabsorbed into the blood. The remaining fluid, containing nitrogenous wastes and excess water and salts, forms urine.
2. What are the methods used by plants to get rid of excretory products?
Plants remove gaseous wastes such as oxygen and carbon dioxide by diffusion through stomata and other surfaces. Excess water is removed through transpiration. Some wastes are stored in cellular vacuoles or in leaves that later fall off. Others are stored as resins and gums, especially in old xylem, while some waste substances are released into the surrounding soil.
3. How is the amount of urine produced regulated?
The amount of urine produced is regulated mainly by selective reabsorption of water in the kidney tubules. When the body has excess water, less water is reabsorbed and more dilute urine is produced. When water is scarce, more water is reabsorbed and a smaller quantity of concentrated urine is formed. Regulation also depends on the amount of dissolved waste that must be removed.
EXERCISES
1. The kidneys in human beings are a part of the system for
(a) nutrition.
(b) respiration.
(c) excretion.
(d) transportation.
(c) excretion.
2. The xylem in plants are responsible for
(a) transport of water.
(b) transport of food.
(c) transport of amino acids.
(d) transport of oxygen.
(a) transport of water.
3. The autotrophic mode of nutrition requires
(a) carbon dioxide and water.
(b) chlorophyll.
(c) sunlight.
(d) all of the above.
(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.
(b) mitochondria.
5. How are fats digested in our bodies? Where does this process take place?
Fats are digested mainly in the small intestine. Bile juice from the liver breaks large fat globules into smaller droplets by emulsification, increasing the surface area for enzyme action. Lipase from the pancreas and intestinal glands then breaks the emulsified fats into fatty acids and glycerol.
6. What is the role of saliva in the digestion of food?
Saliva moistens and lubricates food, making it easier to chew and swallow. It also contains salivary amylase, an enzyme that begins digestion by breaking starch into simpler sugars.
7. What are the necessary conditions for autotrophic nutrition and what are its by-products?
Autotrophic nutrition requires carbon dioxide, water, chlorophyll and sunlight. During photosynthesis, light energy is converted into chemical energy and carbohydrates are formed. Oxygen is released as a by-product. A simplified equation is:
8. What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.
Aerobic respiration occurs in the presence of oxygen, mainly in mitochondria. It completely breaks down glucose into carbon dioxide and water and releases a large amount of energy. Anaerobic respiration occurs without oxygen, usually in the cytoplasm. It incompletely breaks down glucose and releases less energy. Yeast carries out anaerobic respiration to form ethanol and carbon dioxide. Certain bacteria also respire anaerobically, and human muscle cells may temporarily form lactic acid when oxygen is insufficient.
9. How are the alveoli designed to maximise the exchange of gases?
The lungs contain millions of alveoli, providing a very large surface area for gaseous exchange. Each alveolus has a thin, moist wall and is surrounded by numerous blood capillaries. The short diffusion distance, rich blood supply and continuous movement of air maintain concentration differences that allow oxygen and carbon dioxide to diffuse rapidly.
10. What would be the consequences of a deficiency of haemoglobin in our bodies?
A deficiency of haemoglobin reduces the oxygen-carrying capacity of blood. Body cells receive less oxygen for aerobic respiration, so less energy is released. This can cause anaemia, tiredness, weakness, breathlessness, dizziness and reduced ability to perform physical work.
11. Describe double circulation of blood in human beings. Why is it necessary?
In double circulation, blood passes through the heart twice during one complete journey around the body. In pulmonary circulation, deoxygenated blood is pumped from the right ventricle to the lungs, becomes oxygenated and returns to the left atrium. In systemic circulation, oxygenated blood passes from the left ventricle to the body tissues and deoxygenated blood returns to the right atrium. It is necessary because it prevents mixing of oxygenated and deoxygenated blood and supplies oxygen efficiently to meet the high energy needs of the body.
12. What are the differences between the transport of materials in xylem and phloem?
Xylem transports water and minerals mainly upward from the roots to stems and leaves. Its transport is largely driven by root pressure and transpiration pull and usually does not require direct metabolic energy. Phloem transports food, amino acids and other soluble substances from source regions to storage or growing regions. Its movement can occur both upward and downward and requires energy from ATP for loading substances into the phloem.
13. Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.
Both alveoli and nephrons provide large, thin surfaces closely associated with networks of blood capillaries. Alveoli are numerous balloon-like air sacs with thin, moist walls. They exchange gases by diffusion: oxygen enters the blood and carbon dioxide leaves it. Nephrons are numerous filtration units consisting of a glomerulus, Bowman's capsule and a long tubule. They filter blood, selectively reabsorb useful substances and water, and remove nitrogenous wastes and excess salts as urine. Thus, alveoli mainly perform gaseous exchange, whereas nephrons filter blood and regulate its water and dissolved-substance content.