Intext Questions Solved

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

Answer : Multicellular organisms need more oxygen for oxidation of food to release energy. Which cannot be fulfilled by diffusion. So, they have specialised organ system – the respiratory system to meet out the oxygen requirement.

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

Answer : One criterion cannot be used to decide whether something is alive or not alive. We have to consider many criterion of deciding it to be alive such as:

a) Movement of body or body parts (visible to naked eye).
b) Movement of molecules in body (invisible to naked eye).
c) Growth of the body.
d) Occurrence of various life processes.

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

Answer : Raw materials used by an organism are:

  1. (a) Food, (b) Water, (c) Oxygen (in case of animal).
  2. (a) Carbon dioxide, (b) Water, (c) Oxygen, and (d) Energy (in case of plant).

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

Answer : (a) Nutrition, (b) Respiration, (c) Transportation, (d) Growth and repair, (e) Excretion.

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

Answer : 

Autotrophic nutrition Heterotrophic nutrition
1. It is the nutrition in which organic food is manufactured from inorganic raw materials. 2. It is the nutrition in which organic food is obtained from various sources.
2. An external source of energy (sun) is required for synthesis of organic 2. Energy is obtained by oxidation of food (organic substance).
3. The organism lives and depends on inorganic medium. 3. The organism depends and must live in contact with sources of organic matter.
4. The nutrition takes place by synthesis of complex substance from simple molecules. 4. The nutrition is by intake of solid food in some cases.
5. It is found in green plants. 5. It is found in animals, man, non-green plants, fungi, and most of the bacteria.
6. Digestive process is absent. 6. The food is broken down into simpler forms by digestive process.

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

Answer :

Raw materials required for photosynthesis Sources
1. CO2 1. Surroundings – air, water.
2. H2O 2. Soil, water

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

Answer : Role of acid (HCl) in our stomach:

i) It creates an acidic medium needed for action of pepsin enzyme.

ii) It disinfects the food.

Question 4 : What is the function of digestive enzymes?

Answer : Functions of digestive enzymes:

a) To convert the complex food substances into simple molecules.
b) To help in carrying out various life processes by providing materials for it.

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

Answer : Small intestine has several finger-like projections called villi. These are specially adapted/designed for absorption. They have a dense network of blood capillaries and lymph which helps to carry the absorbed food material in blood to different parts of the body.

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

Answer : Aquatic organism obtains its oxygen requirement/demand from the dissolved oxygen (DO) in water. It is comparatively less than the amount of oxygen present freely in the atmosphere. Therefore, terrestrial organisms are at advantage as they directly intake oxygen from air that too in high quality.

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

Answer : 

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

Answer : Oxygen combines with haemoglobin (respiratory pigment) and forms a compound oxyhaemoglobin. Thus, it is transported in a compound state. Carbon dioxide dissolves in water present in blood and is transported in dissolved state in human beings.

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

Answer : Lungs in human beings have air sacs (alveoli). This increases the surface area to about 100 m2 if it is spread out. These structures help in exchange of gases in lungs of human beings, as they are made up of single layer of cells and are very thin to facilitate diffusion of gases.

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

Answer : The components of transport system in human beings.


1. Blood : It transports digested food, oxygen, carbon dioxide and nitrogenous waste materials.

2. Heart : It pumps the deoxygenated blood to lungs for purification and oxygenated blood to different parts of the body tissues.

3. Blood vessels : They carry oxygenated blood to different parts of body tissues and deoxygenated blood to heart for pumping it to lungs for purification.

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

Answer : Animals that maintain their body temperature constant need/ use energy to do so such as birds and mammals. And to get/obtain a constant supply of energy from food, sufficient amount of oxygen is needed at all times which is supplied by oxygenated blood. If oxygenated and deoxygenated blood is mixed in heart chambers, the efficiency of blood in carrying oxygen will decrease resulting in less energy production. This will not allow the animal to maintain its body temperature. Therefore, it is necessary to separate oxygenated and deoxygenated blood in such animals. That is why they have separate chambers for it.

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

Answer : The components of transport system in highly organised plants are:

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

Answer : Water and minerals are transported in plants by xylem tissue.

The xylem tissue is present in roots, stems, branches and leaves. The root cells that are in close contact of soil actively uptake ions. This creates a difference between the concentration of ions in the roots cells and soil.

Due to which, water moves into the root cells to remove this difference. This forms a water column in the root xylem (xylem tissue) and is steadily pushed upwards. It is root pressure.

Also the suction pull developed due to transpiration helps to pull up the water column in plants.

Question 5 : How is food transported in plants?

Answer : The food is transported by phloem tissue in plants. The sieve elements alongwith adjacent companion cells (living) help in movement of substances in both upwards and downwards. The transfer of sucrose in phloem involves utilisation of energy from ATP. Transfer of sucrose from leaf cells to phloem needs energy.

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Question 19 : Describe the structure and function of nephrons.

Answer : Nephron has following regions in it:

i) Bowman’s capsule.
ii) Tubular part.

Millions of nephrons are small tube-like structures present inside the kidney of human. The nephron can be divided into two:

i) Bowman’s capsule : It is a small cup-like structure. It has a tuft made up of a bunch of renal artery. It is called glomerulus or glomerular tuft. The diameter of inlet branch of renal artery is more than the diameter of outlet/ out going branch of renal artery.

ii) Tubular part : The Bowman’s capsule extends into a coiled tube called convoluted tubule. It extends further into a long thin loop. This loop again broadens and terminates into a collecting duct. The collecting duct is attached to many nephrons.

The tubular part of nephron is covered by a network of blood capillaries.

Functions of Nephrons:

Nephrons are called excretory/filtration units. There function is to filter the blood passing through the kidney.

About 180 L of filtrate is filtered by the nephrons but only 1-2L of urine is formed daily.

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

Answer : In plants, excretion is completely different. They do not have excretory system like animals do have. Plants make use of oxygen which is a waste during the process of photosynthesis. Excess of water is removed from the plants stomata. Whereas, wastes like gum, resins, etc., are stored in the dead cells of old xylem tissue. Other wastes are stored in cellular vacuoles and leaves. The leaves that have stored wastes later turn yellow and become dead. Such leaves are dropped by the plant/trees. Some wastes are also released by roots in soil.

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

Answer : The amount of urine released in very less in comparison to the amount filtered by the Bowman’s capsule. It is regulated by the amount of water present in the body. If the body has less water then the urine produced in less and concentrate. If the body has excess of water than the urine produced is excess/frequent and dilute.

Text Book Questions Solved

Question 1 : The kidney in human beings are part of the system for

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

Answer : c) excretion.

Question 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.

Question 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.

Question 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

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

Answer : The fats eaten along with food are big in size, i.e., they have big globules. The enzyme acting on fat does not act properly on big globules. Therefore, these big fat molecules are converted into small globules of fat. It is done by the bile slats present in bile juice secreted by liver. This process is called emulsification of fats. This increases the surface area of small globules and is easily acted upon by the fat digesting enzyme-lipase.

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

Answer : 1. Saliva has an enzyme , salivary amylase/ptyalin, which acts on starch and converts it into maltose.

2. It binds the food particles into ball-like structure and makes it easy to swallow into the food pipe.

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

Answer : Necessary conditions for autotrophic nutrition (photosynthesis) are:

1. Sunlight : Sunlight is necessary for photosynthesis.

2. Chlorophyll : The process of photosynthesis takes place in the presence of chlorophyll. Chlorophyll traps the solar energy and uses it for photolysis of water.

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

Answer : In yeast, bacteria and muscles anaerobic respiration takes place.

Differences between Aerobic and Anaerobic Respiration

Aerobic Respirationq Anaerobic Respiration
1. It is the most common method of respiration which takes place in the higher organisms in the presence of oxygen. 1. It is common in lower organisms and muscle cells of higher organisms in the absence of oxygen.
2. The complete oxidation of glucose takes place to release CO2 + H2O + Energy. 2. The incomplete oxidation of glucose takes place to release alcohol or acid + H2O + Energy
3. It produces more energy per glucose molecule, i.e., 36 ATPs. 3. It produces less energy per molecule, i.e. 2 ATPs.
4. It is completed in cytoplasm and mitochondria of cells. 4. It is completed in cytoplasm only.

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

Answer : Lungs in human beings have air sacs (alveoli). This increases the surface area to about 100 m2 if it is spread out. These structures help in exchange of gases in lungs of human beings, as they are made up of single layer of cells and are very thing to facilitate diffusion of gases.

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

Answer : Haeomoglobin is the respiratory pigment present in blood which combines with oxygen and forms a compound called oxyhaemoglobin. Thus, oxygen is carried by it to the needy tissue cells where it is needed for oxidation for food for release of energy. If haemoglobin is deficient in our body then the oxygen carrying capacity of the blood in body will decrease. This will also lead to less energy production in the body cells.

Consequently, the person will feel or get tired very quickly and also body activities/function may reduce. This condition is called anaemia. The person will become physically weak and turn pale.

Note : Haemoblogin transports oxygen immediately to cells. Without haemoglobin if diffusion if diffusion has to push oxygen in our body, it would 3 years for oxygen molecule to travel from lungs to toes.

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

Answer : The heart chambers are responsible for accepting and pumping for blood. Blood enters the heart two times.

a) Once the blood enters the heart in right half as deoxygenated blood which is pumped to pulmonary aorta and this is done for purification in lungs.

When blood reaches the lungs it is cleaned. The CO2 is removed out from it and O2 is added into it. This makes the blood oxygenated.

b) Second time in left half as oxygenated blood received from pulmonary veins. This has to be pumped to rest of the body for use, i.e., for oxidation of food to release energy.

This is known as double circulation. It is necessary to keep the deoxygenated blood separate and send it for purification so that oxygenated blood is supplied for energy release in tissue cells, constantly every time.

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

Answer : 

Transport of Materials in Xylem Transport of Materials in Phloem
1. The transport of materials in xylem takes place from root cells to leaves. 1. The transport of materials in phloem takes place from leaves/storage organs to other needy organs.
2. Materials are transported due to root pressure and suction pull. 2. Materials are transported due to needs and supply and due to less pressure.
3. Their transportation does not need energy. 3. Their transportation needs energy, e.g., sucrose.
4. The vessels involved in it are mostly dead. 4. The vessels, sieve tubes, companion cells are involved.
5. Materials transported are water and dissolved minerals. 5. Materials transported are sucrose, amino acids and other substances.

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

Answer : 

Functioning of Alveoli Functioning of Nephrons
1. Lungs consists of several air sacs called alveoli. 1. Kidney consists of several nephrons also called filtration units.
2. Air sacs are surrounded by blood capillaries for exchange of respiratory gases – CO2 and O2. 2. Nephrons have blood capillaries called glomerulus in Bowman’s capsule that filter the blood. The capillaries on tubular part absorb the useful materials from filtrate.
3. The air gets packed in the air sacs. The O2 moves into the blood and CO2 moves from the blood to the sacs. This helps in blood purification. 3. This helps in urine formation.