IN TEXT QUESTIONS AND ANSWERS
Page No. 95
Q1. Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?
Ans. The size of the multicellular organisms is very large compare to unicellular organisms. Diffusion is a passive mode of transport of substances and can transfer gases up to a very small distance only. This will not be sufficient for multicellular organisms’ needs.
Q2. What criteria do we use to decide whether something is alive?
Ans. The main criteria to check for life, is the sign of breathing and respiration. If there is no sign of breathing or respirations then the given organism is not alive.
Q3. What are outside raw materials used for by an organism?
Ans. Minerals and water and gases are outside raw materials used by an organism.
Q4. What processes would you consider essential for maintaining life?
Ans. Processes essential for maintaining life are as follows:
Locomotion or movement
Page No. 101
Q1. What are the differences between autotrophic nutrition and heterotrophic nutrition?
Ans. Autotrophic nutrition means that the organism is preparing its own food and is not dependent on any other organism for food. Green plants are autotrophs.
Heterotrophic nutrition means that the organism does not prepare its own food and is dependent on other organisms for food. All organisms which are not among green plants are heterotrophic.
Q2. Where do plants get each of the raw materials required for photosynthesis?
For photosynthesis plants obtain the following raw materials:
(i) Water: Roots absorb it from the soil.
(ii) Carbondioxide: Stomata in leaves allow the carbon dioxide gas to enter into the plant.
(iii) Chlorophyll: It is already present in the leaves.
(iv) Sunlight: From the sun.
Q3. What is the role of acid in our stomach?
Ans. Acid (HCl) present in our stomach makes the medium acidic so as to facilitate the action of the enzyme pepsin and it kills the bacteria ingested with food.
Q4. What is the function of digestive enzymes?
Ans. Digestive enzymes act on the complex food to break them into simpler components.
Q5. How is the small intestine designed to absorb the digested food?
Ans. Small intestine has finger like projection in the inner lining which increases the surface area for absorption of food. These finger like projections are called villi. The villi are richly supplied with blood vessels which take the absorbed food to each and every cell of the body.
Page No. 105
Q1. What advantages over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
Ans. Aquatic organism takes in the oxygen dissolved in water which is in less percentage than the oxygen present in air. Terrestrial organism can take in more amount of oxygen at a time than aquatic organisms.
Q2. What are the different ways in which glucose is oxidised to provide energy in various organisms?
Ans. Breakdown of glucose by various pathways for different organisms are:
Q3. How is oxygen and carbon dioxide transported in human beings?
Ans. Oxygen is carried by haemoglobin present in the RBC of the blood, carbon dioxide is soluble in water and hence is transported by the blood in dissolved form.
Q4. How are lungs designed in human beings to maximise the area for exchange of gases?
Ans. In human beings lungs have the tubes called bronchioles which divide into smaller tubes and terminate into balloon like structures called alveoli. The alveoli provide large surface area where the exchange of gases can take place.
Page No. 110
Q1. What are the components of transport system in human beings? What are the functions of these components?
Ans. In human beings the transport system consists of the following:
(i) Heart: It acts as a pumping organ.
(ii) Blood: It is the transport medium. It is made up of:
(a) Plasma–It carries food molecules, nitrogenous wastes, salts, carbon dioxide, hormones proteins etc. in a dissolved form.
(b) RBC–Consists of haemoglobin and transports oxygen.
(c) WBC–Helps to fight infection.
(d) Platelets–Helps in the clotting of blood.
(iii) Blood vessels:
(a) Arteries–Carry oxygenated blood away from the heart to each and every cell.
(b) Veins–Bring de-oxygenated blood to heart for purification.
Q2. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
Ans. Mammals and birds need large amount of energy for their life processes and hence the oxygenated blood can help them to obtain this energy by breaking down the food.
Q3. What are the components of the transport system in highly organised plants?
Ans. The components of the transport system are xylem. and phloem in highly organized plants.
Q4. How are water and minerals transported in plants?
Ans. Water and minerals are transported in plants with the help of xylem tissue. Roots absorb the water from the soil by actively taking up ions, creates the difference in the concentration of these ions between the root and the soil. Water enters the root cells. The water moves up creating a column of water that is steadily pushed upwards in vessels and tracheids of the roots, stem and leaves, and are interconnected to form a continuous system of water-conducting channels reaching all parts of the plant. The water loss by leaves through stomata is called transpiration. It creates a suction pull, which pulls water from the xylem cells of roots.
Q5. How is food transported in plants?
Ans. The transport of food in plants is called translocation. It takes place with the help of a conducting tissue called phloem. Phloem transports glucose, amino acids and other substances from leaves to root, shoot, fruits and seeds. Sieve tube and companion cells help in transporting the food in upward and downward directions. Sucrose like materials are transported using energy from ATP and osmotic pressure, which is caused due to water. This pressure moves the material in the phloem to tissues which have less pressure. This pressure helps in the movement of material in plants.
Page No. 112
Q1. Describe the structure and functioning of nephrons.
Ans. Structure of nephrons: It consists of a Bowman’s capsule in which glomerulus is present (cluster of capillaries). The afferent artery brings the impure blood to nephron. The cup shaped structure (Bowman’s capsule) form a tubular part of nephron which leads to collecting duct.
Working of Nephron
(i) Filtration: The renal artery or afferent artery is wider and slowly it becomes a narrow tube in the glomerulus. Due to difference in the width, pressure difference is caused and water with dissolved impurities are squeezed out from the tube. It is collected in the Bowman’s capsule which is cup like structure and passes into the tube.
(ii) Reabsorbtion: The above filtrate passes through the tubule where the major amount of water, glucose, amino acids are selectively reabsorbed by the capillaries which are surrounding the tubule.
(iii) Urine formation: The water and impurities which is not reabsorbed is sent to a collecting duct. This filtrate contains more of dissolved nitrogenous wastes i.e. urea and hence it is termed as urine. From here the urine enters the ureter and is collected in urinary bladder.
Q2. What are the methods used by plants to get rid of excretory products?
Ans. Wastes excreted from plants are:
(i) Gaseous wastes–through stomata pores CO2 is given out during respiration and O2 is given out during photosynthesis.
(ii) Liquid wastes (water)–through stomata pores by transpiration.
(iii) Other wastes–are stored in leaves dead cells and the leaves fall off. Some other waste products are stored as resins and gums in old xylem of the plant and other wastes are also thrown out from nodes into the soil.
Q3. How is the amount of urine produced regulated?
Ans. The amount of urine produced depends on how much excess water there is in the body and how much of dissolved waste there is to be excreted. On a hot day, when we sweat and lose a lot of body water and salts, most of the water and salts in kidney will be reabsorbed into the blood from the filtrate in the tubule. Thus the volume of urine produced will be less.
In winters, when we do not sweat a lot, a litre water and salts will be reabsorbed and the volume of urine produced will be more.
Thus there is perfect osmoregulation in the body.
Q1. The kidneys in human beings are parts of the system for
Ans. (c) excretion
Q2. 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) transport of water
Q3. The autotrophic mode of nutrition requires
(a) carbon dioxide and water
(d) All of the above
Ans. (d)All of the above
Q4. The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
Ans. (b) mitochondria
Q5. How are fats digested in our bodies? Where does this process take place?
Ans. Digestion of fats takes place in the small intestine. Fats entering in the intestine are in the form of large globules. Bile juice breaks down these large globules into smaller globules. Afterwards, fat-digesting enzyme lipase present in pancreatic juice and intestinal juice converts it into fatty acids and glycerol.
Q6. What is the role of saliva in the digestion of food?
Ans. The saliva contains an enzyme called salivary amylase that breaks down starch which is complex molecule into glucose.
Q7. What are the necessary conditions for autotrophic nutrition and what are its by-products?
Ans. Conditions necessary for autotrophic nutrition are:
(iii) Water and
(iv) Carbon dioxide
(i) Oxygen and
Q8. What are differences between aerobic and anaerobic respiration? Name some organisms that use anaerobic mode of respiration.
Ans. Difference between aerobic 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 the cytoplasm.|
|4. It always releases CO2 and H2O.||4. It produces alcohols and CO2.|
|5. It yields a large amount of energy.||5. The 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.
Anaerobic respiration takes place in yeast, some bacteria and some internal parasites like a tapeworm.
Q9. How are the alveoli designed to maximize the exchange of gases?
Ans. The walls of the alveoli are folded and have large surface areas. It contains an extensive network of blood vessels which provide a surface where the exchange of gases can take place.
Q10. What would be the consequence of a deficiency of hemoglobin in our bodies?
Ans. Haemoglobin is a pigment present in RBC. It has a high affinity for oxygen. It carries oxygen from lungs to various tissues which are deficient in oxygen. Presence of less hemoglobin will result in less supply of oxygen to tissues. A person having less hemoglobin will get tired soon and will have a pale look.
Q11. Describe double circulation in human beings. Why is it necessary?
Ans. In mammals and birds, the blood goes through the heart twice during each cycle. This is known as double circulation.
Deoxygenated blood which enters right auricle and then it enters the right ventricle from where it is pumped to lungs for oxygenation. From lungs, after oxygenation, it comes to left auricle and then enters left ventricle from where it is pumped to various parts of the body.
Such system of circulation does not allow mixing of oxygenated and deoxygenated blood which allows the efficient supply of oxygen to the body.
Q12. What are differences between the transport of materials in xylem and phloem?
Ans. Difference between transport in xylem and phloem:
|Transport of materials in xylem||Transport of materials in phloem|
|It helps in the transport of water and minerals to leaves and another part of plant body||It helps in the transport of food from leaves to other parts of the plant body|
|Materials are transported through vessels and tracheids.||Materials are transported through sieve tube.|
|Materials are pulled upwards by transpiration pull.||Food is transported using energy in the form of ATP|
Q13. Compare the functioning of alveoli in the lungs and nephron in the kidneys with respect to their structure and functioning.
Ans. Comparison between alveoli and nephron:
|1. It is the structural and functional unit of lungs,||It is the structural and functional unit of kidneys.|
|2. It is thin walled, has a large surface area and is richly supplied with blood vessels,||It is thin walled, has a large surface area and is richly supplied with blood vessels.|
|3. It removes carbon dioxide from the blood.||It removes nitrogenous wastes from the blood|
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