Chapter 6: Life Processes

Internal Question and Answer:

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

Answer: In multi-cellular organisms like humans, all cells are not in direct contact with the surrounding environment. Diffusion is a slow process and can only transport oxygen over very short distances. Therefore, it cannot supply oxygen quickly enough to all the body’s cells, which require a continuous and rapid supply for their metabolic needs.

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

Answer: We decide whether something is alive based on observable life processes like respiration, growth, excretion, reproduction and movement. A living thing must show cellular organisation and metabolism. However, movement is not always visible, so internal chemical reactions are considered the key criterion for life.

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

Answer: Organisms use external raw materials such as carbon dioxide, water and nutrients for growth, energy production and repair. These materials help build the body and provide energy through metabolic processes. Plants absorb carbon dioxide, water and minerals, while animals consume food and oxygen.

4. What processes would you consider essential for maintaining life?

Answer: The essential processes for maintaining life are nutrition, respiration, transportation and excretion. These processes are crucial because they provide energy and raw materials for the body, distribute these materials to all cells and remove waste products that would otherwise accumulate and become toxic, thereby ensuring the organism’s survival and proper functioning.

Internal question and Answer:

1. What are the differences between autotrophic nutrition and heterotrophic nutrition?

Answer: The differences between autotrophic nutrition and heterotrophic nutrition are :

Autotrophic Nutrition	Heterotrophic Nutrition
(i) Organisms synthesize their own food using inorganic sources like carbon dioxide and water.	(i) Organisms cannot synthesize their own food and depend on autotrophs or other organisms for food.
(ii) Contains chlorophyll (in photosynthetic organisms).	(ii) Does not contain chlorophyll.
(iii) Food is prepared through photosynthesis or chemosynthesis.	(iii) Food is obtained by ingesting or absorbing organic matter.
Example: Green plants, some bacteria.	Example: Animals, fungi, most bacteria.

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

Answer: Plants obtain carbon dioxide () from the atmosphere through stomata, and water () from the soil via roots. Sunlight is absorbed by chlorophyll present in leaves, which also traps solar energy. These raw materials are then used to synthesize food during photosynthesis.

3. What is the role of the acid in our stomach?

Answer: The role of acid (hydrochloric acid) in our stomach is to create an acidic medium that activates the enzyme pepsin for digesting proteins. It also kills harmful bacteria that may enter the stomach along with food, thereby protecting the body from infections.

4. What is the function of digestive enzymes?

Answer: The function of digestive enzymes is to break down complex, large and insoluble food molecules into simpler, small and soluble substances that can be easily absorbed by the blood and transported to all cells of the body. For example, amylase breaks down starch, proteases break down proteins and lipases break down fats.

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

Answer: The small intestine is designed for absorption through its inner lining having millions of tiny, finger-like projections called villi. These villi greatly increase the surface area for efficient absorption of digested food. Each villus contains a network of blood capillaries and a lymph vessel (lacteal) to transport absorbed nutrients to different parts of the body.

Internal Question and Answer:

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

Answer: A terrestrial organism has the advantage of obtaining oxygen more easily because air contains more oxygen than water. Oxygen is also absorbed faster from air since gases diffuse more quickly in air than in water. Therefore, terrestrial organisms do not need to spend as much energy in breathing as aquatic organisms.

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

Answer: Glucose is first broken down into pyruvate (pyruvic acid) in the cytoplasm. This pyruvate is then oxidised in different ways in different organisms to provide energy:

(i) Aerobic respiration in mitochondria:

 

(ii) Anaerobic respiration in yeast (fermentation):

(iii) Anaerobic respiration in muscle cells:

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

Answer: Oxygen is transported in human beings by haemoglobin present in red blood cells. Haemoglobin carries oxygen from the lungs to all body tissues. Carbon dioxide produced in the cells is transported mainly in dissolved form in the blood plasma from the tissues to the lungs, where it is released during exhalation.

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

Answer: The lungs in human beings contain millions of tiny air sacs called alveoli. These alveoli provide a very large surface area for the exchange of gases. Their walls are thin and surrounded by blood capillaries, which help oxygen to enter the blood and carbon dioxide to leave the blood easily.

Internal Question and Answer:

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

Answer: The main components of the transport system in human beings are the heart, blood, and blood vessels.

The functions are:

(i) Heart: It acts as a pumping organ and pumps blood to all parts of the body.

(ii) Blood: It transports oxygen, carbon dioxide, digested food, hormones, and waste materials throughout the body.

(iii) Blood vessels (arteries, veins, and capillaries): Arteries carry blood away from the heart, veins bring blood back to the heart, and capillaries facilitate the exchange of materials.

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

Answer: It is necessary to separate oxygenated and deoxygenated blood in mammals and birds because they are warm-blooded animals and require a large amount of energy to maintain a constant body temperature. Complete separation ensures an efficient supply of oxygen to all body parts, which helps in the effective release of energy during respiration.

3. What are the components of the transport system in highly organized plants?

Answer: The transport system in highly organised plants consists of two main components namely, xylem and phloem. Xylem carries water and minerals from the roots to the rest of the plant, while phloem transports products of photosynthesis (like sucrose) from the leaves to all other parts of the plant.

4. How are water and minerals transported in plants?

Answer: Answer: Water and minerals are transported in plants through the xylem tissue. Root hairs absorb water and minerals from the soil, which then enter the xylem. Transpiration pull, caused by the loss of water vapor from leaves, creates a suction force that draws the water and minerals upward through the xylem vessels to all parts of the plant.

5. How is food transported in plants?

Answer: Food in plants is transported by a process called translocation through the phloem. The soluble products of photosynthesis, mainly sucrose, along with amino acids and other substances, are moved from the leaves to different parts of the plant. This movement occurs in sieve tubes with the help of companion cells and can take place both upward and downward. The process uses energy from ATP and is driven by differences in osmotic pressure, allowing food to reach storage and growing regions as required.

Internal Question and Answer:

1. Describe the structure and functioning of nephrons .

Answer:  The structure of nephrons:
Nephrons are the basic filtration units of the kidneys. Each nephron consists of a cluster of very thin-walled blood capillaries called the glomerulus, which is associated with a cup-shaped structure called Bowman’s capsule. This leads into a long tubular part that collects the filtered fluid and finally connects to the collecting duct.

The functioning of nephrons:
Nephrons filter waste products from the blood to form urine. The blood is filtered in the glomerulus, and the filtrate enters Bowman’s capsule. Useful substances like glucose, amino acids, salts and most of the water are selectively reabsorbed as the filtrate moves through the tubule. The remaining waste, mainly urea along with excess water, forms urine, which is then collected and sent to the urinary bladder.

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

Answer: Plants use different methods to get rid of excretory products:

(i) Waste products are stored in vacuoles or in leaves, bark and fruits which are later shed.
(ii) Some wastes are excreted into the surrounding soil through roots.
(iii) Gaseous wastes are removed through stomata during transpiration.
(iv) Some wastes are converted into harmless substances like resins and gums.

3. How is the amount of urine produced regulated?

Answer: The amount of urine produced is regulated by the reabsorption of water in the nephron tubules. This reabsorption depends on the body's water needs and the amount of dissolved waste to be excreted. When there is excess water in the body, less water is reabsorbed, leading to more dilute urine. On the other hand, if the body lacks water or there is more waste to remove, more water is reabsorbed, producing concentrated urine in smaller amounts. This regulation is controlled by hormones and the nervous system.

Exercise Chapter 6: Life Processes

1. The kidneys in human beings are a part of the system for

(a) nutrition.   (b) respiration.  (c) excretion.  (d) transportation.

Answer : (c) excretion.

[Kidneys are part of the excretory system in human beings, as they help in removing waste products like urea and excess water from the blood in the form of urine.]

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.

Answer :  (a) transport of water.

[Xylem in plants is responsible for carrying water and dissolved minerals from the roots to different parts of the plant.]

3. The autotrophic mode of nutrition requires

(a) carbon dioxide and water.     (b) chlorophyll.    (c) sunlight.    (d) all of the above.

Answer : (d) all of the above.

[Autotrophic nutrition requires carbon dioxide, water, chlorophyll and sunlight to carry out photosynthesis and produce food.]

4. The breakdown of pyruvate to give carbon dioxide, water and energy takes place in

(a) cytoplasm.     (b) mitochondria.      (c) chloroplast.    (d) nucleus.

Answer : (b) mitochondria.

[The complete breakdown of pyruvate in the presence of oxygen occurs in the mitochondria, producing carbon dioxide, water, and a large amount of energy (ATP).]

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

Answer: Fats are digested in our body by the action of bile juice and the enzyme lipase. This process takes place in the small intestine. Bile juice, secreted by the liver and stored in the gall bladder, breaks large fat globules into smaller droplets (emulsification). Then pancreatic lipase (from the pancreas) and intestinal lipase break down the emulsified fats into fatty acids and glycerol, which can be absorbed by the body.

6. What is the role of saliva in the digestion of food?

Answer: Saliva is secreted by the salivary glands and plays an important role in the digestion of food. It contains an enzyme called salivary amylase which breaks down starch into sugar (maltose). Saliva also moistens the food, making it easier to chew and swallow, and helps in lubricating the food bolus for smooth passage through the oesophagus.

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

Answer:Autotrophic nutrition requires carbon dioxide, water, chlorophyll and sunlight as the necessary conditions. In this process, green plants prepare their own food by photosynthesis using these components. The by-products of this process are oxygen, which is released into the atmosphere and sometimes water vapour during transpiration-related processes.

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

Answer: The differences between aerobic and anaerobic respiration are :

Aerobic Respiration	Anaerobic Respiration
(i) Aerobic respiration requires oxygen for the breakdown of glucose.	(i) Anaerobic respiration does not require oxygen; it occurs in the absence of oxygen.
(ii) Aerobic respiration produces a higher amount of energy (ATP) per glucose molecule.	(ii) Anaerobic respiration produces a lower amount of energy (ATP) per glucose molecule compared to aerobic respiration.
(iii) In aerobic respiration, the end products are carbon dioxide and water.	(iii) In anaerobic respiration, the end products vary depending on the organism; common end products include lactic acid, ethanol, and carbon dioxide.

Some organisms that use anaerobic mode of respiration are yeast, some bacteria, and parasitic worms (like tapeworms).

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

Answer: The alveoli are designed to maximise the exchange of gases by providing a large surface area. The lungs contain millions of tiny, balloon-like structures called alveoli, which are surrounded by an extensive network of thin-walled blood capillaries. The walls of the alveoli and the capillaries are extremely thin, allowing oxygen and carbon dioxide to diffuse easily across them. This large surface area combined with thin walls and rich blood supply ensures rapid and efficient exchange of gases.

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

Answer: A deficiency of haemoglobin in our body reduces the oxygen-carrying capacity of the blood. As a result, less oxygen reaches the body cells, leading to weakness, fatigue, dizziness and shortness of breath. This condition is called anaemia. In severe cases, it can affect normal body functioning due to insufficient energy production.

11. Describe double circulation in human beings. Why is it necessary?

Answer: In human beings, the blood goes through the heart twice during each cycle of the body. This is known as double circulation. It consists of:

(i) Pulmonary circulation: Deoxygenated blood from the right ventricle is pumped to the lungs for oxygenation, and the oxygenated blood returns to the left atrium.

(ii) Systemic circulation: Oxygenated blood from the left ventricle is pumped to all body parts, and deoxygenated blood returns to the right atrium.

Double circulation is necessary because it separates oxygenated and deoxygenated blood, which allows for a highly efficient supply of oxygen to the body. This maintains high metabolic rate and body temperature in human beings.

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

Answer: The differences between the transport of materials in xylem and phloem are

Xylem	Phloem
(a) Transports water and minerals from roots to upper parts of the plant.	(a) Transports food (sucrose and amino acids) from leaves to all other parts.
(b) Transport is unidirectional (upward only).	(b) Transport is bidirectional (both upward and downward).
(c) Conducting cells are tracheids and vessels, which are dead at maturity.	(c) Conducting cells are sieve tubes with companion cells, which are living.
(d) Movement occurs due to transpiration pull and root pressure.	(d) Movement occurs due to osmotic pressure gradient (translocation) requiring energy (ATP).

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

Answer: The comparison of alveoli in lungs and nephrons in kidneys :

Structure	Functioning
Alveoli are tiny, balloon-like structures in the lungs with very thin walls and a large surface area, surrounded by blood capillaries.	Alveoli provide a large surface for the exchange of gases. Oxygen from inhaled air diffuses into the blood, and carbon dioxide from blood diffuses into the alveoli to be exhaled.
Nephrons are microscopic tubular structures in the kidneys, consisting of a cup-shaped Bowman’s capsule and a long renal tubule with a network of capillaries.	Nephrons filter blood to remove waste products and form urine. Useful substances are reabsorbed while wastes and excess water are excreted.