Q.1 Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?
Ans: The body structure of multicellular organisms such as humans is very complex. They comprise of specialized cells and tissues for performing various important functions of the body. Unlike the unicellular organisms, multicellular organisms are not in direct contact with surrounding environment. Therefore, simple diffusion will not meet the oxygen requirement of all the cells and tissues.
Q.2 What criteria do we use to decide whether something is alive?
Ans: The most important criteria to decide that something is alive is the movement. All living things move by themselves without any external help. In some cases the movements of living things are quite fast which can be easily observed but in other cases the movements are very slow and hence observed with difficulty. For example – the movements in most of the animals are fast but the movements in plants are usually slow.
Q.3 What are outside raw materials used for by an organism?
Ans : Various outside raw materials used by an organism are as follows:
a. Food for providing energy.
b. Oxygen for breakdown of food to obtain energy.
c. Water for proper digestion of food and other functions inside the body.
Q.4 What processes would you consider essential for maintaining life?
Ans: There are various life processes which are essential for maintaining life. Some of them are as follows:
a. Nutrition
b. Respiration
c. Excretion
d. Transportation
Q.5 What are the differences between autotrophic nutrition and heterotrophic nutrition?
Ans:
Autotrophic Nutrition:
i. Food is synthesized from simple inorganic raw materials such as CO2 and water.
ii. Presence of green pigment (chlorophyll) is necessary.
iii. Food is generally prepared during day time
iv. Example: All green plants and some bacteria
Heterotrophic Nutrition:
i. Food is obtained directly or indirectly from autotrophs. This food is broken down with the help of enzymes.
ii. No pigment is required in this type of nutrition.
iii. Food can be prepared at all times.
iv. Example: All animals and fungi.
Q.6 Where do plants get each of the raw materials required for photosynthesis?
Ans: Plants need the following things for photosynthesis:
(i) Plants get CO2 from atmosphere through stomata.
(ii) Plants absorb water from soil through roots and transport it to the leaves.
(iii) Sunlight is absorbed by the chlorophyll and other green parts of the plant.
Q.7 What is the role of the acid in our stomach?
Ans: Role of Hydrochloric acid in our stomach:
i. It provides an acidic medium in our stomach which is necessary for activation of pepsin enzyme.
ii. It kills germs present in the food.
Q.8 What is the function of digestive enzymes?
Ans : Digestive enzymes such as amylase, lipase, pepsin, trypsin, etc. helps to break the complex food particles into simple ones so that these simple particles can be easily absorbed by the blood and thus transported to all the cells of the body.
Q.9 How is the small intestine designed to absorb digested food?
Ans : The inner lining of small intestine has millions of tiny finger-like projections called villi. These villi increase the surface area for absorption of food and are richly supplied with blood vessels. These blood vessels take the absorbed food to each and every cell of the body where it is used for obtaining energy, building up new tissues and repairing of old tissues.
Q.10 What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
Ans : Terrestrial organisms take up oxygen from the atmosphere whereas aquatic animals that live in water use oxygen dissolved in surrounding water. Since, air dissolved in water has fairly low concentration of oxygen so; the aquatic organisms have to breathe faster to get more oxygen. Terrestrial organisms take oxygen from the oxygen rich atmosphere so, they have much less breathing rate than aquatic organism.
Q.11 What are the different ways in which glucose is oxidized to provide energy in various organisms?
Ans: Glucose is broken down into a three carbon molecule called pyruvate in the cell cytoplasm. Pyruvate is further broken down by different ways to provide energy in various organisms. Pyruvate is broken down in different ways in different organisms as shown below.
i) In yeast cells, during fermentation, pyruvate is converted into ethanol and carbon dioxide in the absence of oxygen.
ii) In mitochondria, breakdown of pyruvate takes place in presence of oxygen to give rise three molecules of carbon dioxide and water.
iii) Sometimes, when there is lack of oxygen, especially during vigorous activity, in our muscles, pyruvate is converted into lactic acid.
Q.12 How are oxygen and carbon dioxide transported in human beings?
Ans:Transport of Oxygen: The respiratory pigment, haemoglobin present in red blood cells takes up the oxygen from the air to the lungs. They, then carry the oxygen to cells and tissues which are deficient in oxygen.
Transport of carbon dioxide: Carbon Dioxide is more soluble in water. Hence, it is mostly transported from body tissues in the dissolved form in our blood plasma to lungs where it diffuses from blood to air in the lungs and then expelled out through nostrils.
Q.13 How are lungs designed in human beings to maximize the area for exchange of gases?
In the lungs, the wind pipe branches into bronchi which, in turn, branches into smaller tubes called bronchioles. Bronchioles have pouch like air-sacs at their ends called alveoli. Each lung contains about 300 – 350 millions of alveoli. The alveoli provides maximum surface area for exchange of gases. They have very thin walls and are surrounded by an extensive network of blood vessels to facilitate exchange of gases.
Q.14 What are the components of the transport system in human beings? What are the functions of these components?
Ans: The main components of the transport system in human beings are the heart, blood, and blood vessels.
(i) Heart receives deoxygenated blood from the various body parts of the body and sends this impure blood to the lungs for oxygenation. After receiving the oxygenated blood, it pumps oxygenated blood to all the parts of the body.
(ii) Blood helps in the transport of oxygen, nutrients, CO2, and nitrogenous wastes throughout the body. WBCs protect the body against infections and diseases.
(iii) The blood vessels (arteries, veins, and capillaries) help in circulating the blood throughout the body.
Q.15 Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
Ans : Warm-blooded animals such as birds and mammals maintain a constant body temperature by cooling themselves when they are in a hotter environment and by warming their bodies when they are in a cooler environment. It is therefore necessary to separate oxygenated and deoxygenated blood to maintain efficient supply of oxygen into the body. Hence, these animals require more oxygen (O2) for more cellular respiration so that they can produce more energy to maintain their body temperature.
Q.16 What are the components of the transport system in highly organised plants?
Ans: The transport system in highly organised plants is composed of vascular tissues, xylem and phloem.
Xylem helps to conduct water and minerals obtained from the soil to the rest of the plant. Phloem transports food materials from the leaves to different parts of the plant body.
Q.17 How are water and minerals transported in plants?
Ans: The plants take in water containing dissolved minerals from the soil through their roots. The roots of a plant have hairs called root hairs which absorb water and minerals from the soil. The root hairs are directly in contact with the film of water in-between the soil particles Water and dissolved minerals get into the root hairs by the process of diffusion. The water and minerals absorbed by the root hairs from the soil pass from cell to cell by osmosis through the epidermis, root cortex, endodermis and reach the root xylem.
The xylem vessels of the root of the plant are connected to the xylem vessels of its stem. So, the water containing dissolved minerals enters from the root xylem vessels into stem xylem vessels. The xylem vessels of the stem branch into the leaves of the plants. So, the water and minerals carried by the xylem vessels in the stem reach the leaves through the branched xylem vessels which enter from the petiole (stalk of the leaf) into each and every part of the leaf. In this way, the water and minerals from the soil reach through the root and stem to the leaves of the plant.
Q.18 How is the food transported in plants?
Ans: The transport of food from the leaves to other parts of the plant is called translocation. The food made in leaves is loaded into the sieve tubes of phloem tissue by using energy from ATP. Water now enters into sieve tubes containing sugar by the process of osmosis due to which the pressure in the phloem tissue rises. This high pressure produced in the phloem tissue moves the food to all the parts of the plant having less pressure in their tissues. This allows the phloem to transport food according to the needs of the plant.
Q.19 Describe the structure and functioning of nephron.
Ans: Nephrons are the basic filtering units of kidneys. Each kidney possesses large number of nephrons, approximately 1-1.5 million. The main components of the nephron are:
(i) Glomerulus
(ii) Bowman’s capsule
(iii) Long renal tubule
Functioning of a nephron:
(i) The blood enters the kidney through the renal artery, which branches into many capillaries associated with glomerulus.
(ii) The water and solute are transferred to the nephron at Bowman’s capsule.
(iii) In the proximal tubule, some substances such as amino acids, glucose, and salts are selectively reabsorbed and unwanted molecules are added in the urine.
(iv) The filtrate then moves down into the loop of Henle, where more water is absorbed.
(v) From here, the filtrate moves upwards into the distal tubule and finally to the collecting duct. Collecting duct collects urine from many nephrons.
Q.20 What are the methods used by plants to get rid of excretory products?
Ans: Plants use the following ways to get rid of excretory products:
i. Many waste products are stored in vacuoles of the cells.
ii. Some waste products are stored in the leaves and they are removed as the leaves fall off.
iii. Some waste products such as resins, tannins and gums are stored in non-functional old xylem or bark.
iv. Plants also excrete some waste products through roots into the soil around them.
v. Plants get rid of excess water through transpiration.
Q.21 How the amount of urine is produced regulated?
Ans : The amount of urine produced depends on the amount of excess water and dissolved wastes present in the body. Some other factors such as habitat of an organism and hormone such as Anti-diuretic hormone (ADH) also regulates the amount of urine produced.
Q.22 How the amount of urine is produced regulated?
Ans : The amount of urine produced depends on the amount of excess water and dissolved wastes present in the body. Some other factors such as habitat of an organism and hormone such as Anti-diuretic hormone (ADH) also regulates the amount of urine produced.
Q.23 Where do the plants get each of the raw materials required for photosynthesis?
Ans: Plants need the following things for photosynthesis:
(i) Plants get CO2 from atmosphere through stomata.
(ii) Plants absorb water from soil through roots and transport it to the leaves.
(iii) Sunlight is absorbed by the chlorophyll and other green parts of the plant.
Q.24 What is the role of the acid in our stomach?
Ans: Role of Hydrochloric acid in our stomach:
i. It provides an acidic medium in our stomach which is necessary for activation of pepsin enzyme.
ii. It kills germs present in the food.
Q.25 What is the function of digestive enzymes?
Ans: Digestive enzymes such as amylase, lipase, pepsin, trypsin, etc. helps to break the complex food particles into simple ones so that these simple particles can be easily absorbed by the blood and thus transported to all the cells of the body.
Q.26 How is the small intestine designed to absorb digested food?
Ans: The inner lining of small intestine has millions of tiny finger-like projections called villi. These villi increase the surface area for absorption of food and are richly supplied with blood vessels. These blood vessels take the absorbed food to each and every cell of the body where it is used for obtaining energy, building up new tissues and repairing of old tissues.
Q.27 What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
Ans: Terrestrial organisms take up oxygen from the atmosphere whereas aquatic animals that live in water use oxygen dissolved in surrounding water. Since, air dissolved in water has fairly low concentration of oxygen so, the aquatic organisms have to breathe faster to get more oxygen. Terrestrial organisms take oxygen from the oxygen rich atmosphere so, they have much less breathing rate than aquatic organism.
Q.28 What are the different ways in which glucose is oxidized to provide energy in various organisms?
Ans: Glucose is broken down into a three carbon molecule called pyruvate in the cell cytoplasm.Pyruvate is further broken down by different ways to provide energy in various organisms.Pyruvate is broken down in different ways in different organisms as shown below:
i.In yeast cells, during fermentation, pyruvate is converted into ethanol and carbon dioxide in the absence of oxygen.
ii. In mitochondria, breakdown of pyruvate takes place in presence of oxygen to give rise three molecules of carbon dioxide and water.
iii. Sometimes, when there is lack of oxygen, especially during vigorous activity, in our muscles, pyruvate is converted into lactic acid.
Q.29 How are oxygen and carbon dioxide transported in human beings?
Ans: Transport of Oxygen: The respiratory pigment, haemoglobin present in red blood cells takes up the oxygen from the air to the lungs. They, then carry the oxygen to cells and tissues which are deficient in oxygen.
Transport of carbon dioxide: Carbon Dioxide is more soluble in water. Hence, it is mostly transported from body tissues in the dissolved form in our blood plasma to lungs where it diffuses from blood to air in the lungs and then expelled out through nostrils.
Q.30 How are lungs designed in human beings to maximise the area for exchange of gases?
Ans: In the lungs, the wind pipe branches into bronchi which, in turn, branches into smaller tubes called bronchioles. Bronchioles have pouch like air-sacs at their ends called alveoli. Each lung contains about 300 – 350 millions of alveoli. The alveoli provides maximum surface area for exchange of gases. They have very thin walls and are surrounded by an extensive network of blood vessels to facilitate exchange of gases.
Q.31 What are the components of the transport system in human beings? What are the functions of these components?
Ans: The main components of the transport system in human beings are the heart, blood, and blood vessels.
(i) Heart receives deoxygenated blood from the various body parts of the body and sends this impure blood to the lungs for oxygenation. After receiving the oxygenated blood, it pumps oxygenated blood to all the parts of the body
(ii) Blood helps in the transport of oxygen, nutrients, CO2, and nitrogenous wastes throughout the body. WBCs protect the body against infections and diseases.
(iii) The blood vessels (arteries, veins, and capillaries) help in circulating the blood throughout the body.
Q.32 Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
Ans: Warm-blooded animals such as birds and mammals maintain a constant body temperature by cooling themselves when they are in a hotter environment and by warming their bodies when they are in a cooler environment. It is therefore necessary to separate oxygenated and deoxygenated blood to maintain efficient supply of oxygen into the body. Hence, these animals require more oxygen (O2) for more cellular respiration so that they can produce more energy to maintain their body temperature.
Q.33 What are the components of the transport system in highly organised plants?
Ans: The transport system in highly organised plants is composed of vascular tissues, xylem and phloem. Xylem helps to conduct water and minerals obtained from the soil to the rest of the plant. Phloem transports food materials from the leaves to different parts of the plant body.
Q.34 How are water and minerals transported in plants?
Ans: The plants take in water containing dissolved minerals from the soil through their roots. The roots of a plant have hairs called root hairs which absorb water and minerals from the soil. The root hairs are directly in contact with the film of water in-between the soil particles Water and dissolved minerals get into the root hairs by the process of diffusion. The water and minerals absorbed by the root hairs from the soil pass from cell to cell by osmosis through the epidermis, root cortex, endodermis and reach the root xylem.
The xylem vessels of the root of the plant are connected to the xylem vessels of its stem. So, the water containing dissolved minerals enters from the root xylem vessels into stem xylem vessels. The xylem vessels of the stem branch into the leaves of the plants. So, the water and minerals carried by the xylem vessels in the stem reach the leaves through the branched xylem vessels which enter from the petiole (stalk of the leaf) into each and every part of the leaf. In this way, the water and minerals from the soil reach through the root and stem to the leaves of the plant.
Q.35 How is the food transported in plants?
The transport of food from the leaves to other parts of the plant is called translocation. The food made in leaves is loaded into the sieve tubes of phloem tissue by using energy from ATP. Water now enters into sieve tubes containing sugar by the process of osmosis due to which the pressure in the phloem tissue rises. This high pressure produced in the phloem tissue moves the food to all the parts of the plant having less pressure in their tissues. This allows the phloem to transport food according to the needs of the plant.
Q.36 The kidneys in human beings are a part of the system for
(a) nutrition.
(b) respiration.
(c) excretion.
(d) transportation.
Ans: (c) In human beings, the kidneys are a part of the system for excretion.
Q.37 The xylem in plants are responsible for
(a) transport of water.
(b) transport of food.
(c) transport of amino acids.
(d) transport of oxygen.
Ans: (a) In a plant, the xylem is responsible for transport of water.
Concept insight: Remember the functions of various vascular tissues.
Q.38 The autotrophic mode of nutrition requires
(a) carbon dioxide and water.
(b) chlorophyll.
(c) sunlight.
(d) all of the above.
Ans: (d) The autotrophic mode of nutrition requires carbon dioxide, water, chlorophyll and sunlight.
Q.39 The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
(a) cytoplasm.
(b) mitochondria.
(c) chloroplast.
(d) nucleus.
Ans: (b) The breakdown of pyruvate to give carbon dioxide, water and energy takes place in mitochondria.
Q.40 How are fats digested in our bodies? Where does this process takes place?
Ans: Fats are present in the form of large globules in the small intestine. The small intestine gets the secretions in the form of bile juice and pancreatic juice respectively from the liver and the pancreas. The bile salts (from the liver) break down the large fat globules into smaller globules so that the pancreatic enzymes can easily act on them. Lipase enzyme present in the pancreatic juice causes breakdown of emulsified fats. Glands present in the wall of small intestine secrete intestinal juice which contains lipase enzyme that converts fats into fatty acids and glycerol. This is referred to as emulsification of fats. It takes place in the small intestine.
Q.41 What is the role of saliva in the digestion of food?
Ans: Saliva is secreted by salivary glands, located under the tongue. It moistens the food for easy swallowing. It contains a digestive enzyme called amylase, which breaks down starch into sugar.
Q.42 What are the necessary conditions for autotrophic nutrition and what are its by-products?
Ans: Conditions necessary for autotrophic nutrition are:
(i) Carbon dioxide,
(ii) Water
(iii) Chlorophyll pigment
(iv) Sunlight
Carbohydrates (food) and O2 are the by-products of photosynthesis.
Q.43 What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.
Ans:
Aerobic respiration:
i. Aerobic respiration takes place in the presence of oxygen.
ii. Complete breakdown of food occurs in aerobic respiration.
iii. The end products in aerobic respiration are carbon dioxide and water.
iv. Aerobic respiration produces a considerable amount of energy.
Anaerobic respiration:
i. Anaerobic respiration takes place in the absence of oxygen.
ii. Partial breakdown of food occurs in anaerobic respiration.
iii. The end products in anaerobic respiration may be ethanol and carbon dioxide (as in yeast plants), or lactic acid (as in animal muscles).
iv. Much less energy is produced in anaerobic respiration.
Yeast and bacteria uses anaerobic mode of nutrition.
(i) Differences should always be written in tabular form.
(ii) Differences should be written in terms of their significance.
(iii) Write only those many numbers of differences as stated in the question.
(iv) Give example wherever possible.
Q.44 How are the alveoli designed to maximise the exchange of gases?
Ans: The alveoli have a structure specialised for efficient gaseous exchange:
(i) Walls are extremely thin.
(ii)They have a large surface area in relation to volume.
(iii) They are surrounded by numerous blood capillaries.
Q.45 What would be the consequences of deficiency of haemoglobin in our bodies?
Haemoglobin is the respiratory pigment that transports oxygen to the body cells for cellular respiration. Therefore, deficiency of haemoglobin in blood can affect its oxygen supplying capacity. This can lead to deficiency of oxygen in the body cells as a result of which the person suffers from anaemia, breathing problems and exhaustion.
Q.46 Describe double circulation in human beings. Why is it necessary?
A circulatory system in which the blood travels twice through the heart in one complete cycle of the body is called double circulation.
Importance of double circulation:
The separation of oxygenated and de-oxygenated blood allows a more efficient supply of oxygen to the body cells. This efficient system of oxygen supply is very useful in warm-blooded animals such as human beings. Warm-blooded animals have to maintain a constant body temperature by cooling themselves when they are in a hotter environment and by warming their bodies when they are in a cooler environment. Hence, they require more O2SSS for more respiration so that they can produce more energy to maintain their body temperature. Thus, the circulatory system of humans is more efficient because of the double circulatory heart.
Q.47 What are the differences between the transport of materials in xylem and phloem?
Ans:
Xylem:
i. Xylem conducts water and dissolved minerals from roots to leaves and other parts of the plant.
ii. In xylem, transport of materials take place through vessels and tracheids which are dead tissues.
iii. Movement of water and dissolved materials is also called ascent of sap.
iv. Movement of water is mainly achieved by transpiration pull and no energy is required.
Phloem:
i. Phloem conducts prepared food materials from leaves to other parts of plant in dissolved form.
ii. In phloem, transport of materials take place through sieve tubes with the help of companion cells, which are living cells.
iii. Transportation of food in plants is also called translocation of food.
iv. Translocation of food requires energy in the form of ATP.
Concept insight: (i) Differences should always be written in tabular form.
(ii) Differences should be written in terms of their significance.
(iii) Write only those many numbers of differences as stated in the question.
(iv) Give example wherever possible.
Q.48 Compare the functioning of alveoli in the lungs and nephron in the kidneys with respect to their structure and functioning.
Ans:
Alveoli Struture:
Alveoli are small sac-like structures present inside the lungs.
The walls of the alveoli are one cell thick and it contains an extensive network of blood capillaries.
Alveoli Function:
Gas exchange of oxygen and carbon dioxide takes place in the alveoli.
Nephron Structure:
Nephrons are tubular structures present inside the kidneys.
Nephrons are made of glomerulus, Bowman’s capsule, and a long renal tube. It also contains a cluster of thin-walled blood capillaries.
Nephron Function:
Nephrons principal function is to control the absorption of water and soluble substances such as sodium salts by filtering the blood, reabsorbing what is required and excreting the rest as urine.
Q.49 What criteria do we use to decide whether something is alive?
Ans: The most important criteria to decide that something is alive is the movement. All living things move by themselves without any external help. In some cases the movements of living things are quite fast which can be easily observed but in other cases the movements are very slow and hence observed with difficulty. For example – the movements in most of the animals are fast but the movements in plants are usually slow.
Q.50 What are outside raw materials used by an organism?
Various outside raw materials used by an organism are as follows:
a. Food for providing energy.
b. Oxygen for breakdown of food to obtain energy.
c. Water for proper digestion of food and other functions inside the body.
Q.51 What processes would you consider essential for maintaining life?
There are various life processes which are essential for maintaining life. Some of them are as follows:
a. Nutrition
b. Respiration
c. Excretion
d. Transportation