Chapter 5

                                                                        Life Processes 

Intext questions : (page no. 81) 

1. Why is diffusion insufficient to meet the oxygen requirements of multicellar organisms like humans? 

Ans. In case of a single celled organism, no specific organs for exchange of gases needed because the entire surface of the organism is in contact with the environment.

— Where as in multicellular organisms, all the cells may not be in direct contact with the surrounding environment.

— Thus diffusion is insufficient to meet the oxygen requirements of large multicellular organisms because the volume of humanbody is so big that oxygen cannot diffuse into all the cells of the humanbody rapidly.

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

Ans. Movement (Running, walking etc.)

— Respiration

— Display of growth and development

— Excretion

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

Ans. Outside raw materials provide energy to organisms to maintain their body process. They are needed to prevent damage and break-down in the body.

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

Ans. The important processes essential for maintaining nutrition, respiraton, transportation, life are excretion and control and co-ordination.

Intext questions : (page no. 87)

1. Write differences between Autotropic nutrition and Heterotropic nutrition. Where do plants get the raw materials needed for photosynthesis ? 

Ans. The raw materials needed for photosynthesis such as CO₂ and H₂O are obtain as follow.

— Plants receives carbon-dioxide (CO₂) from the atmosphere.

— Plants receive water (H₂O) through roots from the soil.

2. What is the role of acid in our stomach ?

Ans. Hydrochloric acid (HCl) in the stomac produces an acidic medium. Which helps the process of enzyme pepsin.

— It also destroys the bacteria that enter stomach with food.

— It dissolves insoluble salts.

3. What is the function of digestive Enzymes ? 

Ans. Saliva contains an enzyme called salivary amylase, which converts complex molecules of starch food into sugar (maltose)

— Pancreas secretes pancreatic juice which contains enzymes such as amylase, trypsin and lipase enzymes.

— Amylase digest starch

— Trypsin digests proteins.

— Lipase digests fat

— The walls of the small intestine contain glands which secrete intestinal juice.

— The enzymes present in it finally converted the proteins to amino acid, complex carbohydrates into glucose and fats into fatty acid and glycerol.

4. How is the small intestine designed to absorb digested food?

Ans. Small finger like projection villi are located in the wall of the small intestine for the absorption of digested food or substance which increase the surface area of the small intestine.

— The large number of blood vessels present in villi which absorb food and deliver it to every cell in the body.

(Page no. 91)

1. 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 obtain oxygen from water. Air contains more oxygen as compared to water. Since the content of oxygen in the air is high, the terrestrial animals do not have to breathe faster to get more oxygen.

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

Ans. The first six carbon atom of glucose decomposes into a three carbon atom pyruvate.

In absence of Oxygen (O₂):-

— Here pyruvate is converted in ethanol and carbon-dioxide.

— This action occurs during fermentation in yeast.

— This action takes place in the absence of oxygen, which is called anaerobic respiration.

In the presence of Oxygen (O₂):-

— Here, pyruvate decomposes into particles using oxygen in mitocondria.

— This action decomposes the molecules of three carbon pyruvate into three molecules of carbon dioxide and water.

— This process which takes place in the presence of oxygen it is called Aerobic respiration.

In lack of Oxygen:

— When our muscle cells are deficient in oxygen, pyruvate decomposes and converts into three carbon atoms lactic acid.

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

Ans. (i) Transport of oxygen : Haemoglobin present in the blood takes up the oxygen from the air in the lungs. It carries the oxygen to tissues which are deficient in oxygen before releasing it.

(ii) Transport of carbon dioxide : Carbon dioxide is more soluble in water. Therefore, it is mostly transported from body tissues in the dissolved form in our blood plasma to lungs. Here it diffuses from blood to air in the lungs.

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

Ans. The exchange of gases can take place on the surface which is provided by the alveoli.

— The walls of the alveoli are supplied with an extensive network of blood vessels.

— So lungs maximize the area for a gaseous exchange through the presence of large numbers of alveoli which are richly supplied with blood.

— To make a gas exchange in lungs the alveoli are adapted to happen easily and efficiently.

— The lungs are really given a big surface area by them. Just one cell thick and they have thin walls that are moist.

— There are a lot of tiny blood vessels which are called capillaries.

— In the lungs, the presence of alveoli with shape can further increase the surface area and cause a large surface area.

— A short diffusion distance of alveolar walls is one cell thick providing gases a thin wall.

— Gases dissolve in the moisture helping them to pass across the gas exchange surface of moist walls.

(Page no. 96)

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

Ans. The components of the transport system in human beings are the heart, blood, and blood vessels.

— The function of the heart is to pump oxygenated blood throughout the body and receives deoxygenated blood from the various body parts and sends this impure blood to the lungs for oxygenation.

— Blood has three main functions: transport, protection, and regulation. Blood transports the following substances: Gases, namely oxygen (02) and carbon dioxide (CO₂), between the lungs and rest of the body.

— Nutrients from the digestive tract and storage sites to the rest of the body.

— The function of blood vessels is to transport blood throughout the body.

1. Arteries Blood is carried away from the heart to various organs at high pressure.

2. Veins Blood is transported to the heart from various organs at low pressure.

3. Capillaries: Blood is carried from arteries to veins.

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

Ans. The mammals and birds are warm blooded animals which have high energy needs because they constantly require energy to maintain their body temoerature. It is necessary to separate oxygenated blood and deoxygenated blood in mammals and birds because such a separation allows a highly efficient supply of oxygen to the body cells which is required for producing a lot of energy needed by them.

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

Ans. The two components of transport in highly organised plants are xylem and phloem.

 Xylem tissue is made of dead cells in the form of xylem vessels and tracheids. It tranports water and dissolved minerals from roots to all the parts of the plant.

— In xylem the transport is unidirectional.

 Phloem tissue is made of living cells in the form of sieve tubes and companion cells. It transports food made in leaves by photosynthesis to all the parts of a plant.

— In phloem the transport food is bidirectional.

4. How are water and minerals transported in plants?

Ans. Xylem tissue transports water and mineral in plants.

— Xylem vessels and tracheids of root, stem and leaves are interconnected to form a continuous system of water and minerals conducting channels to each part of the plant.

— The root hair present in the soil absorb water from the soil by osmosis.

— The entry of water dilutes the contents of the root hair vacuole so that it becomes weaker than its neighbour. 

— Therefore water passes into the next cell which in turn becomes diluted, finally water enters the xylem vessel.

— This creates a column of water that is steadily pushed upward, called root pressure.

— There is a continuous loss of water through stomata of the leaves in the form of water vapour. This process is called transpiration.

— The water lost due to transpiration is taken up from the xylem vessels and tracheids in the leaves.

5. How is food transported in plants?

Ans. Translocation is defined as the process of transport of food from the leaves to other parts of the plant.

— Transportation is a vital process in all living organisms and is involved in the movement of water, minerals and other necessary nutrients to all parts of the plant.

— In plants, the synthesized food molecules by the leaves are transported to the different storage organs- roots, stem, and fruits.

— The phloem are the complex living tissue present in all vascular plants and are mainly composed of different specialized cells called such as-companion cells, phloem fibers, phloem parenchyma cells and sieve tubes.

— Phloem helps in translocation of food materials from the leaves to parts of the plant.

— Phloem transports food in both directions, upwards and downwards.

— ATP is required in the form of energy for transportation.

(Page no. 98)

1. Describe the structure and functioning of nephrons.

Ans. Nephron is the basic functional unit of kidneys that consists of a glomerulus and its associated tubules through which the glomerular filtrate passes before it emerges as urine.

Structure of nephrons : 

— It consists of a Bowman’s capsule in which glomerulus is present. The different arteries brings the impure blood to nephron. The cup shaped structure form a tubular part of nephron which leads to collecting duct.

Working of Nephron:

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.

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.

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

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

Ans. Plants consume water for their life processes; however, The excess water is expelled through the process of transpiration.

— Other excretory wastes get accumulated in the cell vacuoles, eventually forming resin and gum. Some of these wastes are stored in the leaves which later droop and wither away.

— Carbon dioxide or gaseous wastes are eliminated through stomata.

— Some other forms of wastes can be excreted into the soil. Excretory products can also be stored as oils and latex in the barks of trees.

3. 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 little water and salts will be reabsorbed and the volume of urine produced will be more. Thus there is perfect osmoregulation in the body.

                                                                        Exercise

 

1. The kidneys in human beings are a part of the system for

(a) nutrition                              (c) excretion.

(b) respiration                          (d) transportation.

Ans. (c) excretion 

2. The xylem in plants are responsible for

(a) transport of water                     (c) transport of amino acids.

(b) transport of food                       (d) transport of oxygen.

Ans. (a) transport of water.

3. The autotrophic mode of nutrition requires

(a) carbon dioxide and water                                (c) sunlight.

(b) chlorophyll                                                         (d) all of the above.

Ans. (d) all of the above.

4. The breakdown of pyruvate to give carbon dioxide, water and energy takes place in

(a) cytoplasm                           (c) chloroplast.

(b) mitochondria                     (d) nucleus.

Ans. (b) mitochondria

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

Ans. The pancreatic juice, which contains enzyme such as amylase, trypsin and lipase.

— The enzyme lipase digest fat.

— This process takes place in the small intestine.

6. 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.

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

Ans. In autotrophic nutrition to take place the 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 by product of the autotrophic nutrition is oxygen which is released through stomata.

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

Ans. Aerobic respiration :

— The reaction takes place in presence of oxygen.

— Its end products are carbon dioxide and water.

— More energy is released.

— It takes place in cytoplasm and mitochondria.

— Complete oxidation of glucose takes place.

Anaerobic respiration :

— The reaction takes place in absence of oxygen.

— Its end products are ethanol and carbon dioxide.

— Less energy is released.

— It takes place only in the cytoplasm.

— Incomplete oxidation of glucose takes place.

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

Ans. The alveoli are thin-walled, balloon like structure and richly supplied with a network of blood vessels to facilitate the exchange of gases between blood and the air-filled in alveoli. They have a balloon-like structure that provides maximum surface area for exchange of gases.

10. 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.

11. Describe double circulation of blood in human beings. Why is it necessary?

Ans. It is the process during which blood passes twice through the heart during one complete cycle.

— The separation of oxygenated and deoxygenated blood allows a more efficient supply of oxygen to the blood cells.

— Blood is circulated to the body tissue through systemic circulation and to the lungs through the pulmonary circulation.

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

Ans. Xylem :

— Water and mineral are transported.

— The transport in unidirectional.

— Vessels and tracheids are dead cells.

— Water transport by transpiration process.

Phloem :

— Food transport.

— The transport food in bidirectional.

— Sieve tubes and companion cells are living cells.

— Food transport by translocation process.

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

Ans. Alveoli in lungs :

— It is the structural and functional unit of lungs.

— It is thin walled, has a large surface area and is richly supplied with blood vessels.

— It removes carbon dioxide from the blood.

Nephron in the Kidney :

— It is the structural and functional unit of kidneys.

— It is thin walled, has a large surface area and is richly supplied with blood vessels.

— It removes nitrogenous wastes from the blood.