IN TEXT QUESTIONS (PAGE 95)
1: Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans.
Ans: In multi-cellular organisms, all the cells may not be in direct contact with the surrounding environment. Thus, simple diffusion will not meet the requirements of all the cells.
2: What criteria do we use to decide whether something is alive.
Ans:Any visible movement such as walking, breathing, or growing is generally used to decide whether something is alive or not. However, a living organism can also have movements, which are not visible to the naked eye. Therefore, the presence of molecular movement inside the organisms used to decide whether something is alive or not
3: What are outside raw materials used for by an organism.
Ans: An organism uses outside raw materials mostly in the form of food (Since life on earth depends on carbon based molecules, most of these food sources are also carbon-based) and oxygen. The raw materials required by an organism can be quite varied depending on the organism and its environment
4: What processes would you consider essential for maintaining life.
Ans: Life processes such as nutrition, respiration, transportation, excretion, etc. are essential for maintaining life.
IN TEXT QUESTIONS (PAGE 101)
1: What are the differences between autotrophic nutrition and heterotrophic nutrition.
Ans:
| Autotrophic nutrition
1. Food is made from simple inorganic raw materials such as CO2 and water. 2.Presence of green pigment (chlorophyll) is necessary.. 3. Food is generally prepared during day time. 4. All green plants and some bacteria have this type of nutrition. . |
Heterotrophic nutrition
1. Food is obtained directly or indirectly from autotrophs. 2.No pigment is required in this type of nutrition 3. Food can be prepared at all times.
4.All animals and fungi have this type of nutrition |
2: Where do plants get each of the raw materials required for photosynthesis.
Ans:
The following raw materials are required for photosynthesis:
(a) The raw material CO2 enters from the atmosphere through stomata in the leaves.
(b) Water is absorbed from the soil by the plant roots.
(c) Sunlight, an important component to manufacture food, is absorbed by the chlorophyll and other green parts of the plants.
3: What is the role of the acid in our stomach.
Ans: Role of the acid (HCl) in our stomach:
(a) Kills germs present in the food.
(b) Makes the food acidic, so that enzyme pepsin can digest protein.
4: What is the function of digestive enzymes.
Ans: Digestive enzymes such as amylase, lipase, pepsin, etc. help in the breaking down of complex food particles into simple ones. These simple particles can be easily absorbed by the blood and thus transported to all the cells of the body.
5: How is the small intestine designed to absorb digested food.
Ans: The small intestine has millions of tiny finger-like projections called villi. These villi increase the surface area for food absorption. Within these villi, many blood vessels are present that absorb the digested food and carry it to the blood stream. From the blood stream, the absorbed food is delivered to each and every cell of the body.
IN TEXT QUESTIONS (PAGE 105)
1: What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration.
Ans: Since the amount of dissolved oxygen is fairly low compared to the amount of oxygen in the air, the rate of breathing in aquatic organisms is much faster than terrestrial organisms. Therefore, unlike aquatic animals, terrestrial animals do not have to show various adaptations for better gaseous exchange.
2: What are the different ways in which glucose is oxidised to provide energy in various organisms.
Ans: Glucose is first broken down in the cell cytoplasm into a three carbon molecule called pyruvate. Pyruvate is further broken down in the following ways to provide energy:
3: How is oxygen and carbon dioxide transported in human beings.
Ans: The haemoglobin pigment present in the blood gets attached to oxygen molecules that are obtained from breathing. It thus forms oxy haemoglobin and the blood becomes oxygenated. This oxygenated blood is then distributed to all the body cells by the heart. After giving away oxygen to the body cells, blood takes carbon dioxide which is the end product of cellular respiration. Now the blood becomes de-oxygenated. Since haemoglobin pigment has less affinity for carbon dioxide, It is mainly transported in the dissolved form. This de-oxygenated blood gives carbon dioxide to the alveoli in the lungs and takes oxygen in return.
4: How are the lungs designed in human beings to maximize the area for exchange of gases.
Ans: The exchange of gases takes place between the blood capillaries that surround the alveoli and the gases present in the alveoli. Thus, alveoli are the site for exchange of gases. The lungs get filled up with air during the process of inhalation as ribs are lifted up and diaphragm is flattened. This fills the numerous alveoli present in the lungs. And increases the surface area for gaseous exchange making the process of respiration more efficient.
IN TEXT QUESTIONS (PAGE 110)
1: 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. Heart pumps oxygenated blood throughout the body. It receives deoxygenated blood from the various body parts and sends this impure blood to the lungs for oxygenation. Blood is a fluid connective tissue, it helps in the transport of oxygen, nutrients, carbon dioxide, and nitrogenous wastes. Blood vessels (arteries, veins, and capillaries) carry blood either away from the heart to various organs or from various organs back to the heart.
2: 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. Hence, these animals require more oxygen for more cellular respiration so that they can produce more energy to maintain their body temperature. Thus, it is necessary for them to separate oxygenated and de-oxygenated blood, so that their circulatory system is more efficient and can maintain their constant body temperature.
3: What are the components of the transport system in highly organized plants.
Ans: In highly organised plants, there are two different types of conducting tissues − xylem and phloem. Xylem conducts water and minerals obtained from the soil (from the roots) to the rest of the plant. Phloem transports amino acids and food materials from the leaves to different parts of the plant body.
4: How are water and minerals transported in plants.
Ans: The components of xylem tissue (tracheids and vessels) of roots, stems and leaves are interconnected to form a continuous system of water conducting channels that reaches all parts of the plant. Transpiration creates a suction pressure, as a result of which water is forced into the xylem cells of the roots. Then there is a steady movement of water from the root xylem to all the plant parts through the water conducting channels.
5: How is food transported in plants.
Ans: Phloem transports food materials from the leaves to different parts of the plant body. The transportation of food in phloem is achieved by utilizing energy from ATP. As a result of this, the osmotic pressure in the tissue increases causing water to move into it. This pressure moves the material in the phloem to the tissues which have less pressure. This pressure is helpful in moving materials according to the needs of the plant. For example, the food material, such as sucrose, is transported into the phloem tissue using ATP energy
IN TEXT QUESTION (PAGE 112)
1: Describe the structure and functioning of nephrons.
Ans: Nephrons are the basic filtering units of kidneys. Each kidney possesses large number of nephrons, approximately 1 to 1.5 million. The main components of the nephron are glomerulus, Bowman’s capsule, and a long renal tubule.
Functioning of a nephron: The blood enters the kidney through the renal artery, which branches into many capillaries associated with glomerulus. The water and solute are transferred to the nephron at Bowman’s capsule. Here some substances such as amino acids, glucose, and salts are selectively reabsorbed and unwanted molecules are added in the urine. From here, the filtrate moves upwards into the distal tubule and finally to the collecting duct. which collects urine from many nephrons. The urine formed in each kidney enters a long tube called ureter. From ureter, it gets transported to the urinary bladder and then into the urethra.
DIAGRAM: Structure of nephron
2: What are the methods used by plants to get rid of excretory products.
Ans: (i) Plants can get rid of excess water by transpiration. For other wastes, plants use the fact that many of their tissues consist of dead cells, and that they can even lose some parts such as leaves.
(ii) Many plant waste products are stored in cellular vacuoles. Waste products may be stored in leaves that fall off. Other waste products are stored as resins and gums, especially in old xylem.
(iii) Plants also excrete some waste substances into the soil around them.
3: How is the amount of urine 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.
IN TEXT QUESTIONS EXERCISES (PAGE 113)
1: The kidneys in human beings are a part of the system for (a) nutrition. (b) respiration. (c) excretion. (d) transportation.
Ans: (c) for 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.
Ans: (a) for transport of water.
3: The autotrophic mode of nutrition requires
(a) carbon dioxide and water. (b) chlorophyll.
(c) sunlight. (d) all of the above.
Ans: (d) carbon dioxide, water, chlorophyll and sunlight
4: The breakdown of pyruvate to give carbon dioxide, water and energy takes place in (a) cytoplasm. (b) mitochondria. (c) chloroplast. (d) nucleus.
Ans: (b) in mitochondria.
5: How are fats digested in our bodies. Where does this process take 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. This is referred to as emulsification of fats. It takes place in the small intestine.
6: What is the role of saliva in the digestion of food.
Ans: Saliva is secreted by the salivary glands, located under the tongue. It makes the food soft for easy swallowing. It contains a digestive enzyme called salivary amylase, which breaks down starch into sugar.
7: What are the necessary conditions for autotrophic nutrition and what are its by-products.
Ans: Autotrophic nutrition takes place through the process of photosynthesis. Carbon dioxide, water, chlorophyll pigment, and sunlight are the necessary conditions required for autotrophic nutrition. Carbohydrates (food) and O2 the by-products of photosynthesis. 6 CO2 + 6H2O ( chlorophyll and sunlight) → C6H12O6 + 6O2
8: What are the differences between aerobic and anaerobic respiration. Name some organisms that use the anaerobic mode of respiration.
Ans:Difference between Aerobic respiration and Anaerobic respiration:
| Aerobic respiration | Anaerobic respiration |
| 1. It occurs in the presence of O2. | 1. It occurs in the absence of O2 |
| 2.It involves the exchange of gases between the organism and the outside environment. | 2.Exchange of gases is absent. |
| 3. It occurs in cytoplasm and mitochondria | 3. It occurs only in cytoplasm |
| 4.It always releases carbon dioxide and water. | 4.It produces alcohols and carbon dioxide |
| 5. It yields large amount of energy | 5. Energy released is very low |
Anaerobic respiration occurs in the roots of some waterlogged plants, some parasitic worms, animal muscles and some micro-organisms such as yeasts.
9: How are the alveoli designed to maximise the exchange of gases.
Ans: The alveoli are the small balloon-like structures present in the lungs. The walls of the alveoli consist of extensive network of blood vessels. Each lung contains 300−350 million alveoli. The alveolar surface when spread out covers about 80 m2 area. This large surface area makes the gaseous exchange more efficient.
10: What would be the consequences of a deficiency of haemoglobin in our bodies.
Ans: Haemoglobin is the respiratory pigment that transports oxygen to the body cells for cellular respiration. Therefore, deficiency of haemoglobin in blood can affect the oxygen supplying capacity of blood. This can lead to deficiency of oxygen in the body cells. It can also lead to a disease called anaemia.
11.Describe double circulation in human beings. Why is it necessary.
Ans: Since both oxygen and carbon dioxide have to be transported by the blood, the heart has different chambers to prevent the oxygen-rich blood from mixing with the blood containing carbon dioxide. The human heart is divided into four chambers − the right atrium, the right ventricle, the left atrium and the left ventricle. Oxygen-rich blood from the lungs comes to the thin-walled upper chamber of the heart on the left, the left atrium. The left atrium relaxes when it is collecting this blood. It then contracts, while the next chamber, the left ventricle, expands, so that the blood is transferred to it. When the muscular left ventricle contracts in its turn, the blood is pumped out to the body. De-oxygenated blood comes from the body to the upper chamber on the right, the right atrium, as it expands. As the right atrium contracts, the corresponding lower chamber, the right ventricle, dilates. This transfers blood to the right ventricle, which in turn pumps it to the lungs for oxygenation. During this process blood goes twice through the heart. That’s why it is known as double circulation.
Double Circulation is necessary: 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. Hence, they require more oxygen 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.
12: What are the differences between the transport of materials in xylem and phloem.
Ans: Difference between Xylem and Phloem:
| Xylem | Phloem |
| 1. Xylem tissue helps in the transport of water and minerals | . 1. Phloem tissue helps in the transport of food.
|
| 2.Water is transported upwards from roots to all other plant parts. | 2.Food is transported in both upward and downward directions |
| 3. Transport in xylem occurs with the help of simple physical forces such as transpiration pull | 3. Transport of food in phloem requires energy in the form of ATP
|
13: Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.
Ans:.
| Alveoli | Nephron |
| 1. Alveoli are tiny balloon-like structures present inside the lungs | 1. Nephrons are tubular structures present inside the kidneys |
| 2. it contains an extensive network of blood capillaries | 2. It contains a cluster of thin walled capillaries. |
| 3. Alveoli are the site of gaseous exchange. | 3. Nephrons are the basic filtration unit
|
| 4. It removes carbon dioxide from the blood. | 4. It removes nitrogenous waste from the blood. |