Life Processes-NCERT Solutions

Q1.  Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?

Ans. In multicellular organisms all the cells may not be in direct contact with the surrounding environment. Hence diffusion will not meet all the requirements of all the cells.

Q2.  What criteria do we use to decide whether something is alive?

Ans. Movement in response to external stimuli, breathing, growth etc.

Q3.  What are outside raw materials used for by an organism?

Ans. Outside raw materials are used for maintenance and sustenance of life by an organism.

Q4.  What processes would you consider essential for maintaining life?

Ans. All processes that perform the maintenance function of living organisms are called life processes. All life processes are essential for maintaining life.

Q5.  What are the differences between autotrophic nutrition and heterotrophic nutrition?

Q6.  Where do plants get each of the raw materials required for photosynthesis?

Ans. 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.

Q7.  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.

Q8.  What is the function of digestive enzymes?

Ans. Digestive enzymes act on the complex food to break them into simpler components.

Q9.  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.

Q10.  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.

Q11.  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:

              

Q12.  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.

Q13.  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.

Q14.  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.

Q15.  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.

Q16.  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.

Q17.  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.

Q18.  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.

Q19.  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.

Q20.  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.

Q21.  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 litde 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 a part of the system for

          (a)  nutrition.

(b)  respiration.

(c)  excretion.

(d)  transportation.

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.

(b)  chlorophyll.

(c)  sunlight.

(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

          (a)  cytoplasm.

(b)  chloroplast. (c) mitochondria.

(d)  nucleus.

Ans. (c) mitochondria.

Q5.  How are fats digested in our bodies? Where does this process take place?

Ans. Fats are digested in the small intestine. The secretion of liver, called bile, breaks down the large globules of fat into smaller globules. This is called emulsification of fats. The bile also makes the medium alkaline so that the pancreatic enzyme containing lipase further digest fats to form fatty acids. The alkaline medium is required for pancreatic enzyme to act on lipase.

Q6.  What is the role of saliva in the digestion of food?

Ans. Saliva contains enzymes, salivary amylase and is released in our mouth. It breaks down starch into sugar (complex carbohvdrates into simpler ones).

Q7.  What are the necessary’ conditions for autotrophic nutrition and what are its byproducts?

Ans. For autotrophic nutrition to take place the conditions necessary are light, carbon dioxide and water should reach a cell which contains chlorophyll in it. Water first splits to release oxygen and hydrogen. This process is photolysis of water. Hydrogen then combines with carbon dioxide to form glucose.

          The byproduct of the autotrophic nutrition is oxygen which is released through stomata.

Q8.  What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.

          Some organisms that use the anaerobic mode of respiration are—yeast and bacteria.

Q9.  How are the alveoli designed to maximise the exchange of gases?

Ans. The alveoli are present at the terminal of bronchioles. They are balloon shaped structures which increases the surface area for the exchange of gases and are richly supplied with blood vessels to take the oxygen to different cells.

Q10.  What would be the consequences of a deficiency of haemoglobin in our bodies?

Ans. Haemoglobin is a red pigment present in our blood which carries oxygen to all the parts of the body.

           If there is deficiency of haemoglobin then amount of oxygen reaching our body cells will decrease.

           Which may lead to release of less energy in our body, leading to a disease called anaemia.

           Breathlessness, tiredness and weakness are the symptoms of anaemia.

Q11.  Describe double circulation in human beings. Why is it necessary?

Ans. The heart of human beings consist of two sides right and left.

           The right side of the heart receives de-oxygenated blood from the cells and tissues and sends it further for purification to lungs.

           The left side of the heart receives oxygenated blood from lungs which is pumped further and sent to all the parts of the body through blood vessels. This is called double circulation. The energy demand of human beings is too large and hence it is necessary for the separation of oxygenated and deoxygenated blood to meet this energy demand.

Q12.  What are the differences between the transport of materials in xydem and phloem?

Q13. Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.