Improvement in food resources

                                                          Class-IX                                                   Biology

1.    What do we get from cereals, pulses, fruits and vegetables?

Ans- Cereals provide carbohydrates.

         Pulses provide proteins.

         Fruits provide vitamins, minerals and sugars (glucose/fructose).

          Vegetables provide vitamins, minerals, fibers and carbohydrates.

2.    How do biotic and abiotic factors adverse affect crop production?

Ans- a. Biotic factors:

          i. Cattle, rodents and insects feed on standing crop and destroy either crop plants or their produce.

         ii. Nematodes, bacteria, viruses and fungi destroy crop by causing various diseases.

           b. Abiotic factors: Drought, water- logging, cold, frost, hailstorm, day length, acidity or alkalinity of soil, etc, influence growth and flowering in plants.

3.    What are desired agronomic characteristics for crop improvement?

Ans- Agronomic features:

a.     For cereals plants: short in height, profuse branching and short maturation period.

b.     For legume crops: Extensive branching for bearing more pods and more foliage.

c.      For fodder crops: tall plants with intensive branching, good foliage and juicy stem.

4.    What are macronutrients and why are they called macronutrients?

Ans- Macronutrients are essential inorganic elements required by plants in relatively large quantities for growth and reproduction. They are called macronutrients because they ate required in relatively large quantities,    e.g., Carbon, Hydrogen, Oxygen, nitrogen, phosphorus, potassium, calcium, etc.

5.    How do plants get nutrients?

Ans- Plant get nutrients from air, water and soil. Carbon and oxygen are obtained from air, hydrogen from water and remaining 13 essential elements Nitrogen , phosphorous, potassium, calcium, Magnesium , Sulphur, Iron, Manganese, Boron, zinc, copper, Molybdenum and chlorine from soil through absorption along with water.

6.    Compare the use of manure and fertilizers in maintaining soil fertility.

Ans- Manure contains organic substances. It is degraded and absorbed easily by plants. It increases and prolongs the fertility of soil without causing any harm. However, manure contains small quantity of minerals salts and is not nutrients –specific.

The chemical fertilizers, on the other hand, contain nutrients in considerable amount but improve the soil fertility for a short duration. Continuous use of fertilizers destroys the natural soil fertility potential and also degrades the environment.

7.    Why should preventive measures and biological control methods be preferred for protecting crops?

Ans- Both preventive and biological control methods are preferred for protecting crops because:

a.     They are environment friendly.   c. They are target- specific.

b.     They do not cause pollution.        d. They are harmless to other life forms.

8.    What factors may be responsible for loss of grains during storage?

Ans- Factor responsible for the loss of stored grains are both abiotic and biotic.

Abiotic factors include improper temperature of store house, humidity of air and high moisture content of the grains. Improper containers for storage also cause loss of grains.

Biotic factors include infestation of insects; infestation with mites, birds, rodents; diseases caused by microorganisms and enzymes action that occur within stored food grains.

9.    Which method is commonly used for improving cattle breeds and why?

Ans- Cattle breeds are improved by cross breeding between indigenous breed and exotic breeds. The indigenous breeds are hardy and resistant to several diseases, and exotic breeds have high- milk yield and longer lactation period. The progeny resulting from cross breeding contains the desirable traits of both the breeds.

10. Discuss the implication of the following statement:

“It is interesting to note that poultry is India’s most efficient converter of low fiber food stuff (which is unfit for human consumption) into highly nutritious animal protein food.”

Ans- The agriculture wastes produced during food processing, e.g. rice bran, fish meal, oil cakes are unfit for human consumption. These are utilized as poultry feed. Poultry birds effectively convert these substances into highly nutritious eggs and meat rich in animal protein.

11. What management practice is common in dairy and poultry farming?

Ans- The common management practices adopted in dairy and poultry farming are:

a.     Providing shelter, rich feed and clean drinking water.

b.     Maintain optimum temperature and good hygienic conditions in farmhouse and poultry farm.

c.      Providing health care and timely vaccination to farm animals.

12. What are the differences between broilers and layers and their management?

Ans- Broilers are young chickens of 6-10 weeks of age. They grow fast and are used as meat which is of good quality and good taste. The layers are sexually mature hens which are raised to lay eggs.

Management: Broilers are given protein – rich food with adequate amount of fat and vitamins. They are provided good space, adequate temperature and best of the hygiene. The layers are given comparatively poor quality of feed. Temperature regulation is not required but they are given plenty of light.

13. Explain any one method of crop production which ensures high yield.

Ans- To increases crop production, various agricultural practices like mixed cropping, intercropping, crop rotation hybridization, etc. are in use. If same crop is grown year after year, it creates deficiency of certain nutrients in the soil and soil loses its fertility. Crop rotation helps in restoring fertility. It involves growing different types of crops on the same piece of land in a specific succession. Crops chosen are such that when one withdraws nutrients from soil, the other crop replenishes them. If crop rotation is done properly, two or three crops can be grown in a year with good yield.

14. Why are manures and fertilizers used in fields?

Ans- Manures and fertilizers are added to enhance and enrich the soil with both organic and inorganic nutrients. Manures also provide porosity to the soil, increase its water retention and enhance activity of microorganisms.

15. What are the advantages of intercropping and crop rotation?

Ans- Intercropping:

1.     Intercropping ensures greater crop yield.

2.     It helps in better utilization of natural resources (land, water, nutrients and sunlight).

3.     It prevents soil erosion.

4.     Each crop can be harvested threshed and marketed separately at different times.

5.     Since different crops are sown in separate rows and mature at different times, there is no mixing of produce of these crops.

6.     Intercropping saves time and labor of the farmer.

Crop rotation:

1.     The soil fertility is maintained for longer period.

2.     The chemical nature of soil is not altered.

3.     It helps in weed and pest control through breaking the cycle by rotation of crop variety.

4.     Crop rotation saves a lot of nitrogen fertilizer and land is not left free of cultivation. As a result, 2-4 crops are raised per year. This increases income of farmers.

16. What is genetic manipulation? How is it useful in agricultural practices?

Ans- Genetic manipulation is transfer of one or more desirable genes from    one plant of same or other species or variety to another. The transfer of gene may be carried out by cross breeding, mutation breeding or recombinant DNA technology. Through genetic manipulation, high yielding and disease resistant crop varieties can be produced.

17. How do storage grains losses occur?

Ans- Losses of stored grains may occur due to a) high moisture content of grains and increased humidity in air provide suitable environment for the growth of microorganisms which in turn disintegrate the food grains . b) Insects pests and enzymatic activity also damages stored grains leading to their loss. c) Rodents, birds feed on grains. d) Weevils, Pulse borers, Khapra beetles also damage by boring or feeding on stored grains.

18. How do good animal husbandry practices benefit farmers?

Ans- Good animal husbandry practices benefit farmers by:

a.     Good hygiene protects cattle and other animals from infectious diseases.

b.     Clean and spacious shelter keeps animals healthy.

c.      Proper healthy diet enhances growth and yield of livestock.

d.     Segregation of sick animals protects other livestock.

e.     Vaccination prevents and protects young animal products like milk, eggs and meat.

f.       Prevents loss of livestock due to diseases.

19. What are the benefits of cattle farming?

Ans- a. farming of milk animal, such as cow, buffalo, goat and camel provide us with milk and milk byproducts like ghee, butter, paneer, etc. Use of exotic and hybrid varieties has resulted in White revolution.

        b. Farming of draught animals, such as bullocks provide animals for agricultural purposes, such as tilling, irrigation and transport of food grains.

        c. Growing fodder for cattle enriches soil.

        d. Organic waste generated by cattle farming can be used for manure.

        e. It provides extra income.

20. For increasing production, what is common in poultry, fisheries and bee-keeping?

Ans- The common features among poultry, fisheries and bee-keeping are:

a)     Good quality of breeds.

b)    Good, nutritious food.

c)     Proper clean, airy and well-lighted accommodation.

d)    Proper medical and health care to control diseases.

21. How do you differentiate capture fishing, mariculture and aquaculture?

Ans- Capture fishing

a.     In capture fishing, the fishes are collected from various natural sources such as rivers, ponds, lakes and seas.

b.     No seeding or rearing of fish is required.

  Mariculture

a.     In mariculture, the marine fishes, shellfishes and sea weeds are cultured in coastal water.

b.     Fish and other organisms are seeded and reared.

Aquaculture

a.     In aquaculture, economically important freshwater plants and animals, including fishes, are cultured in freshwater reservoirs.

b.     Fish and other organisms are seeded and reared.

                                         
                                            Assignment -2

                                             Life processes

                                           

     Class -10                                                                                     Biology 

1.     What are stomata and lenticels? Discuss their role in exchange of gases in plants.

2.     How are alveoli designed to maximize the diffusion of respiratory gases?

3.     A farmer floods his field every day thinking that watering in this manner will result a better yield of his wheat crop. What will be the result of this action of the farmer?

4.     Blood plasma is yellow, then why is blood red in color?

5.     Two green plants are kept separately in oxygen free containers, one in dark and the other in continuous light, which one will live longer? Give reasons.

6.     Plants growing in arid regions have deep roots and sunken stomata. Why?

7.     To demonstrate the process of transpiration by the bell jar experiment, Vaseline is applied on the brim of the bell jar? Explain why?

8.     Which organisms are called natural purifier of air?

9.     Why is chlorophyll extracted from the leaf before testing it for the presence of starch?

10.   Stomata of desert plants remain closed during the daytime. How do they take up carbon dioxide and perform photosynthesis?

11.   Leaves of a healthy potted plant were coated with Vaseline to block the stomata. Will this plant remain healthy for long? State three reasons for your answer.

12.   Why is freshly prepared lime water used in an experiment to demonstrate evolution of co₂ during respiration?

13.    White blood corpuscles are called ‘soldiers of the body’. Why?

14.   Lack of oxygen in muscles often leads to cramps among cricketers. Explain. Why?  

15.   In an activity to demonstrate that ascent of sap takes through xylem tissue, a student’s placed an uprooted plant in a beaker filled with colored water. After 4-5 hours, he cut a section of its stem and observed it under a microscope. What will he see and what can be concluded from that?

16.   What happens to rate of breathing during vigorous exercise and why?

                              Assignment-1 (Biology)

                              Chapter- Life processes                            class-10

Answer the following questions:

1.     What are life processes?

2.     What is the universal source of energy for all living organisms?

3.     What kind of reactions takes place in biochemical processes?

4.     What is nutrition? Write its importance.

5.     What are the stored forms of food in plants and animals?

6.     Write down the 3 steps of photosynthesis. What is the role of co₂ in photosynthesis?

7.     How do stomata open and close? Write the structural features of guard cells which help in closing and opening of stomata.

8.     Name 4 elements that are absorbed by plants from soil.

9.     Name any 2 parasitic plants.

10.   Where is food digested in Amoeba?

11.   Write down the various changes that take place during digestion in following organs:-

i)                   Mouth cavity     ii)    Duodenum    iii)    stomach 

12.   What are peristaltic movements? Where do they take place?

13.   Why do different animals have different lengths of small intestine?

14.   Explain that small intestine is the most suitable organ for the process of absorption.

15.   Name 2 steps of cellular respiration and write the site where they take place.

16.   Differentiate between Alcoholic fermentation and lactic acid fermentation.

17.   What happens to energy which is released during oxidation of glucose?

18.   Why do aquatic organisms have faster breathing rate as compared to terrestrial organisms?

19.   What happens to inhaled air inside the Nasal cavity?

20.   What is residual volume? Write its importance.

21.   What is the need for respiratory pigment in multicellular organisms?

                                                  Life processes (biology)

                                                             class X

1.      Why is diffusion insufficient to meet the oxygen requirement of multicellular organisms like us?

Ans- In unicellular organisms, single cell of the body is in direct contact with the environment. The oxygen from atmosphere diffuses into the body cell. But in multicellular organisms, all the body cells are not exposed to the environment. Deep –seated body cells may not get oxygen through diffusion. Cell to cell diffusion is very slow. Therefore, multicellular organisms need specialized organs for breathing and obtaining oxygen (respiratory system) and a system to distribute oxygen to all the body cells (circulatory system).

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

Ans- On the basis of following characteristics, a living organism is different from non living objects:

a.      All living beings are made up of a cell or cells (cellular organization).

b.      Living beings respire by inhaling oxygen and exhaling carbon dioxide (respiration).

c.       Living beings need food for energy needed to perform life activities (nutrition).

d.      Living beings exhibit growth and development, and respond to stimuli.

e.      All living beings exhibit certain kind of movements either visible or invisible.

f.        All living beings increase their number through reproduction.

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

Ans- The raw materials used by an organisms are: oxygen (for respiration and production of energy, i.e. ATP), Food (for energy, growth and maintenances of body), Minerals and Vitamins (for proper maintenance of body), Carbon dioxide (In case of autotrophs for synthesis of food through photosynthesis), Water (to take part in all physiological processes).

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

Ans- Life processes essential for maintaining life are metabolisms, nutrition, respiration, excretion, transportation, control and coordination and reproduction.

5.      What are differences between autotrophic nutrition and heterotrophic nutrition?

Ans-

s.n	Autotrophic nutrition	Heterotrophic nutrition
1. 2.  3. 4.	Autotrophs manufacture their own food from inorganic substances. These possess photosynthetic pigments for trapping light. These convert light energy into chemical energy. Examples: All green plants, cyanobacteria.	1. Heterotrophs obtain their food from outside utilizing organic substances. 2.  These lack photosynthetic pigments for trapping light. 3. These do not convert light energy into chemical energy. 4. Examples: Animals, humans, parasites and fungi.

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

Ans- a. Carbon dioxide: from air through stomata.

                b. Water: from soil, by absorption through roots.

           c. Minerals: from soil, by absorption along with water through roots.

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

Ans- Hydrochloric acid present in gastric secretion plays an important role in the process of digestion.

a.      HCL acidifies food for the action of the gastric enzyme pepsin.

b.      It converts inactive pepsinogen and prorennin in active pepsin and rennin.

c.       HCL kills the harmful bacteria present in the food.

d.      It stops action of enzymes salivary amylase.

8.      What is the function of digestive enzymes?

Ans- Digestive enzymes help in breaking down complex food materials into simpler compounds which can be readily used by animals through absorption and assimilation. As such, digestive enzymes help in converting proteins into amino acids, fats into fatty acids and glycerol and polysaccharides into monosaccharides.

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

Ans- a. The mucosa of small intestine is folded and projected in the form of finger- like structures, the villi, which increases the absorptive surface area manifolds.

                 b.Villi are highly vascular containing blood capillaries.

                  c. Epithelial lining of small intestine is very thin. Its cells have microvilli which increase surface of absorption.

10.  What advantages does a terrestrial organism have over aquatic organisms with regard to obtaining oxygen for respiration?

Ans- Terrestrial organisms obtain atmospheric oxygen, while aquatic organisms thrive on the oxygen, dissolved in water. Air contains about 21% oxygen while water has less than 1% oxygen. Oxygen diffuses through water much slower than in air. Therefore, a terrestrial organism takes greater amount of oxygen at a faster rate with lesser efforts. While an aquatic organism has to exert more efforts to obtain the same amount of oxygen and breathes faster.

11.  What are the different ways in which glucose is oxidized t6o provide energy in various organisms?

Ans- The first step in energy production is the breakdown of glucose (6-carbon compound) into two pyruvate molecules (3-c compound) by glycolysis. It occurs in the cytoplasm. It is common to all types of respiration. The fate of pyruvate (pyruvic acid) depends upon the presence or absence of oxygen.

a.      In presence of oxygen: Pyruvate is oxidized into carbon dioxide and water using oxygen. The process takes place in mitochondria and produces 36 ATP molecules (Aerobic respiration).

b.      In absence of oxygen: In some bacteria and fungi, pyruvate is converted into ethyl alcohol and carbon dioxide. This process takes place in yeast. It is called fermentation or anaerobic respiration.

c.       In case of lack of oxygen: In case of lack of oxygen, pyruvate breaks up into lactic acid. This usually happens in skeletal muscles of human beings during vigorous exercise.

12.  How are oxygen and carbon dioxide transported in human being?

Ans- a. Transport of oxygen: Most of the oxygen (97%) is carried by haemoglobin as oxyhaemoglobin in the erythrocytes (RBC’s ). By oxyhaemoglobin oxygen is transported from lung capillaries to the different cells and tissues of the body. About 3% of the oxygen gets dissolved in blood plasma.

           b. Transport of carbon dioxide: Co₂ is transported in blood in three forms:

i. As bicarbonate : Most of the carbon dioxide (70-85%) is transported by blood plasma in the form of bicarbonate of sodium and potassium .

ii. As Carbaminohaemoglobin: About 10-23 % Co₂  combines with haemoglobin to form carbaminohaemoglobin.

 iii. Dissolved in plasma: About 5-7% gets dissolved in plasma.

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

Ans- Human lungs have a highly branched network of respiratory tubes. A primary bronchus divides into secondary bronchi, which in turn forms tertiary bronchi. Tertiary bronchi divide repeatedly into bronchioles which finally terminate into alveoli. Alveoli have extremely thin wall and posses a network of capillaries for the exchange of gases. The alveoli provide a vast surface area for exchange of gases. It is estimated that the total surface area of alveoli of human lungs is about 80 square meters.

14.  What are the components of the transport system in highly organized plants?

Ans- In highly organized plants transport system consists of xylem and phloem.

a.      Xylem transports water and minerals and its components are xylem vessels, xylem tracheids, xylem parenchyma and xylem fibers.

b.      Phloem translocates food substance. Its components are sieve tubes, companion cells, and phloem parenchyma and phloem fibers.

15.  How are water and minerals transported in plants?

Ans- In xylem tissue, vessels and tracheids of the roots, stem and leaves are interconnected to form a continuous system of water conducting channels reaching all parts of the plant.

 The water along with dissolved minerals from root hairs, passes into xylem vessels through cells of the cortex, endodermis and pericycle and then ascent of sap takes place from xylem of the root to the xylem of stem and leaves through vessels and tracheids. Evaporation of water molecules from the cells of leaves (transpiration) creates a suction which pulls the water from the root towards the upper parts of the plant.

16.  How is food transported in plants?

Ans- Food from the area of its manufacture enters into sieve tubes of phloem and gets transported as a dilute aqueous solution. The movement of nutrients can be in upward or downward direction. Companion cells of the phloem help in the process. The transport of nutrients occurs through physical forces but entry and exist of nutrients from the phloem occurs only through an active process utilizing energy from ATP. Entry of nutrients into phloem increases the osmotic pressure of the tissue, causing water to move into it due to endosmosis. The pressure moves the materials in the phloem to tissues which have less pressure. In this way, according to plant’s requirement, the nutrients get translocated.

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

Ans- Human transport system has Blood vascular system and Lymphatic system. Blood vascular system consists of heart, blood vessels and blood.

a.      Heart is a muscular pumping organ which pumps the circulating medium (blood). It maintains continuous flow of blood in the blood vessels.

b.      Blood vessels are tubes through which blood flows. Blood vessels are of three types:

i.                    Arteries: They carry oxygenated blood from the heart to different parts of the body.

ii.                  Veins: They transport deoxygenated blood from the heart to different parts of the body.

iii.                Capillaries: They help in exchanges of materials between blood and living cells through tissue fluid.

c.       Blood consists of plasma and corpuscles (RBCs, WBCs and platelets)

i.                    Plasma is the fluid matrix of blood. Its helps in transport of hormones, nutrients, excretory matter, etc.

ii.                  RBCs help in transport of respiratory gases O₂ and CO₂.

iii.                WBCs kill pathogens by engulfing them or by producing antibodies.

iv.                 Platelets help in blood clotting.

Lymphatic system: It is a network of thin walled lymphatic. It consists of lymph, lymphatic vessels and lymph nodes.

a.      Lymph transports respiratory gases, fatty acids, glycerol, vitamins, etc.

b.      Lymphatic vessels collect lymph and transport it to the veins.

c.       Lymphatic nodes help in the formation of lymphocytes.

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

Ans- Mammals and birds are warm- blooded animals. They have to maintain a constant and higher body temperature. Therefore, their energy requirement is more and the metabolic rate of their body is higher than those of the other animals. To meet this demand of energy, they need more and efficient oxygen supply. For this, it is necessary to keep separate the oxygenated and deoxygenated blood so that the required amount of oxygen could be made available to the cells and tissues.

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

Ans- Metabolic wastes produced in plants are eliminated through the following methods:

a.      Excess water is eliminated by transpiration.

b.      Respiratory waste (CO₂), and photosynthesis waste (O₂) are expelled through stomata.

c.       Waste products may be stored in leaves, bark or any other parts of the plant which are shed off.

d.      Resins, gums, tannins, alkaloids like morphine, quinine, etc, which are waste products are stored in plants.

e.      In some plants, e.g., Zamikand, wastes remains present in leaves in the form of crystals of calcium oxalate.

20.  Describe the structure and functioning of nephrons.

Ans- Nephrons are the structural and functional units of the kidneys. Each nephron is a tubular structure differentiated into: (a) a cup – like Bowman’s capsule and (b) a long renal tubule. In the cup of Bowman’s capsule is present a network of capillaries called glomerulus. The Bowman’s capsule continues into the renal tubules. Different parts of the renal tubule are proximal convoluted tubule, the ’U- shaped loop of Henle, the distal convoluted tubule, the collecting tubules and collecting ducts.

The function of nephron is filtration of blood and elimination of waste materials. Blood, along with waste materials, is brought to glomerulus through afferent arteriole. The Bowman’s capsule filters this blood and pours the filtrate into renal tubules as renal filtrate. From this filtrate, useful substances and a large amount of water is reabsorbed by blood capillaries surrounding it. Nitrogenous and other wastes, along with a little amount of water, are sent to the urinary bladder through the uterus. The urinary bladder expels the urine to the outside through the urethra.

21.  How the amount of urine is is produced regulated?

Ans- The volume of urine produced by kidneys is regulated by a hormone secreted from the posterior part of pituitary gland. This hormone is          antidiuretic hormone (ADH) or vasopressin. This hormone induces reabsorption of water from the nephric filtrate.

If enough amount of water is present in blood, small amount of ADH is secreted and more urine is formed. If lesser amount of water is present in the blood, more ADH is secreted, more water is reabsorbed from the nephric filtrate in the peritubular capillaries surrounding nephron, and hence less urine is produced.

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

Ans- a. Fat is first emulsified by bile juice in duodenum. During emulsification, larger fat molecules are broken into smaller droplets to provide enough surfaces for the action of enzymes lipase.

b. The emulsified fat is acted upon by pancreatic lipase in duodenum where fat is hydrolyzed and broken down into fatty acids and glycerol.

Emulsified fat                               Fatty acids and glycerol

Remaining undigested fat when reaches ileum is acted upon by lipase enzyme present in succus entericus (intestinal juice) and is digested into fatty acid and glycerol.

                   Fat                          Fatty acid and glycerol

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

Ans- Saliva carries out following functions:

a.      It moistens and softens the food.

b.      It converts semi- solid food into slippery bolus for easy swallowing.

c.       Salivary amylase (ptyalin) present in saliva starts digestion of starch (polysaccharides and converts it into maltose (disaccharide).

24.  What are the necessary conditions for autotrophic nutrition and what ate it’s by products?

Ans- In autotrophic nutrition, green plants synthesis their own food by the process of photosynthesis

a.      Presence of sunlight and chlorophyll.

b.      Raw materials: carbon dioxide and water.

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

Ans- 

s.n      Aerobic respiration	Anaerobic respiration
1.      Aerobic respiration occurs in the presence of O2 where O2 is utilized. 2.      Glucose is completely broken down to release the end product in the form of CO2 and water. 3.      Energy released in larger amount. 4.      It takes place in cytoplasm and mitochondria.	1. Anaerobic respiration occurs in the absence of O2. 2. Glucose is incompletely oxidized to release the end products in the form of ethanol or lactic acid. 3. Energy is released in lesser amount. 4. It takes place in cytoplasm. The mitochondria are not involved.

        Bacteria and fungi are anaerobic mode of respiration.

26.  How are the alveoli designed to maximize the exchange of gases?

Ans- each lung has about one million alveoli. The wall of alveoli is highly folded and is richly supplied with blood capillaries. This highly vascular enormous surface makes a very efficient organ for gaseous exchange.

27.   What would be the consequences of deficiency of hemoglobin in our bodies?

Ans- Hemoglobin provides oxygen to the tissues and cells of the body for respiration and release energy .Deficiency of hemoglobin is called anemia. In anemia conditions, less amount of O₂ is transported, resulting in insufficient production of energy. An anemic person feels weak and lethargic and gets tired doing even normal physical work.

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

Ans- In double circulation, blood flows twice through heart during each cardiac cycle. Deoxygenated blood from the whole body is brought to the right atrium through the anterior and posterior vena cava. From right atrium, blood is sent to right ventricles and from here is carried to lungs by the pulmonary vein.This is called pulmonary circulation.

From the left atrium, blood goes to the left ventricle which pumps it through the aorta to all the body parts. This is called systemic circulation. Thus, blood flows twice through the heart during a single cardiac cycle, Significance: Double circulation prevents, mixing of oxygenated and deoxygenated blood. Such a separation allows a highly efficient supply of oxygen of oxygen to the body cells. It is necessary for human beings as they have high energy needs for their metabolism to maintain constant body temperature.

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

Ans- Differences in transport of material in xylem and phloem:

s.n        Characteristics	Transport in xylem	Transport in phloem
1.Substances transported 2.Direction of movement   3.    Components   4.    Force   5.    Metabolic inhibitions	Water and minerals. Movement is unidirectional, i.e., only upward movement from root to aerial parts of the plant. Xylem vessels and tracheids. Simple physical forces. Not influenced by metabolic inhibitors.	Organic food. Movement is multidirectional, i.e., both in upward and downward directions. Sieve tube of phloem, helped by companion cells. Energy from ATP is needed. Phloem transport is inhibited.

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

Ans- Differences between alveoli and nephrons:

s.n        Characteristics	Alveoli	Nephrons
1.      Shape 2.       Units of system(presence) 3.      Function 4.      Process involved	Rounded and appear like bunches of grapes. Structural and functional units of lungs (respiratory system). They deal with respiratory gases. Alveoli perform exchange of gases between blood and inhaled air. Diffusion of gases takes place.	Elongated tubules. Structural and functional units of kidneys (excretory system). They deal with body fluid. Nephron brings about separation of nitrogenous waste from blood. Ultrafiltration, selective reabsorption and tubular secretion and involved.