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Lakhmir Singh Class X Biology Chapter 1 – Life Processes


Exercise : Solution of Questions on page Number :23


Answer 1:
Food is the basic requirement of all living organisms for obtaining energy.


Answer 2:
Chemical energy is used by the living organisms to perform their vital life processes.


Answer 3:
Green plant is an autotroph as it can prepare its own food.


Answer 4:
Carbon dioxide and water are the two inorganic substances used by autotrophs to make their food.


Answer 5:
Some fungi are parasitic while most exhibit saprotrophic mode of nutrition.


Answer 6:
Mushrooms have saprophytic mode of nutrition, Cascuta and mistletoe have parasitic mode of nutrition and human beings have holozoic mode of nutrition.


Answer 7:
The process by which plants make food is known as photosynthesis.


Exercise : Solution of Questions on page Number :24


Answer 8:
Presence of sunlight and the green pigment, chlorophyll are the two other conditions necessary for the process of photosynthesis.


Answer 9:
Apart from sunlight and chlorophyll, carbon dioxide and water are also required to make food by photosynthesis.


Answer 10:
(a) Carbon dioxide is used in photosynthesis.
(b) Oxygen is produced in photosynthesis.


Answer 11:
Food A is glucose and food B is starch.


Answer 12:
Alcohol is used to remove chlorophyll from a green leaf during photosynthesis experiments.


Answer 13:
We boil the leaf in alcohol when we are testing it for starch to remove the chlorophyll from it and decolourise it.


Answer 14:
(a) In leaves, the pigment that absorbs the energy of sunlight is chlorophyll.
(b) This pigment is green in colour.


Answer 15:
The pigment that can absorb solar energy is chlorophyll.


Answer 16:
Chloroplast is the organelle of plant cells where photosynthesis takes place.


Answer 17:
Apart from carbon dioxide and water, plants require nitrogen, phosphorus, iron and magnesium.


Answer 18:
Chlorophyll is mainly present in the chloroplasts, which are present in the photosynthetic cells of green plants.


Answer 18:
Chlorophyll is mainly present in the chloroplasts, which are present in the photosynthetic cells of green plants.


Answer 20:
Amoeba is an organism whose process of obtaining food is called phagocytosis.


Answer 21:
On the basis of their eating habits, animals are divided into herbivores, carnivores and omnivores.


Answer 22:
(i) Carnivores are only meat eaters.
(ii) Herbivores are only plant eaters.
(iii) Omnivores are both plant and meat eaters.


Answer 23:
Chlorophyll is the green pigment present in the leaves of a plant.


Answer 24:
The correct order of the processes involved in the nutrition of animals is given below:
Ingestion → Digestion → Absorption → Assimilation → Egestion


Answer 25:
Amoeba engulfs the food particle by forming finger-like projections around it, which are known as pseudopodia.


Answer 26:
Digestive enzymes enter into the food vacuole in Amoeba to break down the food.


Answer 27:
Undigested food is egested through the cell membrane in an Amoeba .


Answer 28:
Paramecium uses cilia to move food particles into its mouth.


Answer 29:
Salivary amylase is present in human saliva. Starch is partially digested by this enzyme.


Answer 29:
Salivary amylase is present in human saliva. Starch is partially digested by this enzyme.


Answer 31:
Food moves in the digestive organs through peristaltic movement.


Answer 32:
Food pipe is also known as oesophagus.


Answer 33:
When we chew our food, saliva gets mixed with food in the mouth.


Answer 34:
The tiny projections on the inner surface of the small intestine that help in absorbing the digested food are known as villi.


Answer 35:
Water is absorbed in the large intestine.


Answer 36:
The opening in the human body through which the undigested food is thrown out is known as anus.


Answer 37:
In the human body, the digested food is absorbed into the blood in the small intestine.


Answer 38:
Enzymes are the biological catalysts that bring about the chemical digestion of food.


Answer 39:
(a) All green plants are autotrophs.
(b) All non-green plants and animals are heterotrophs.
(c) Heterotrophs depend on autotrophs and other heterotrophs for food.
(d) Green plants use carbon dioxide and water to make food.
(e) Iodine turns blue-black on reacting with starch.


Exercise : Solution of Questions on page Number :25


Answer 40:
(a) Chlorophyll is the green pigment present in the chloroplasts of the cells of green plants. It absorbs sunlight for photosynthesis.
(b) (i) In the process of photosynthesis, glucose is prepared first.
(ii) Starch is stored in plant leaves.


Answer 41:
(a) Movement is the criteria used to decide whether something is alive.
(b) The basic functions performed by the living organisms to maintain their life on the Earth are known as life processes. The basic life processes common to all living organisms and essential for maintaining life are nutrition, growth, movement, respiration, transportation, reproduction, excretion and control and coordination.


Answer 42:
(a) The organisms that prepare their food themselves are known as autotrophs. Green plants are autotrophs.
(b) The presence of chlorophyll, carbon dioxide, water and sunlight are the conditions necessary for autotrophic nutrition.


Answer 43:
(a) Organisms that depend upon autotrophs and other heterotrophs for their food are known as heterotrophs. Animals are heterotrophs.
(b)

Autotrophic nutrition Heterotrophic nutrition
The mode of nutrition in which an organism prepares its own food with the help of simple inorganic materials like water and carbon dioxide from the surroundings is known as autotrophic nutrition. The mode of nutrition in which an organism cannot prepare its own food and depend upon other organisms for its food is known as heterotrophic nutrition.

Answer 44:
(a) A nutrient is an organic or inorganic substance required for the maintenance of life and survival of the living organisms. Four important nutrients present in our food are carbohydrates, proteins, vitamins and fats.
(b) The various types of heterotrophic nutrition are saprophytic, parasitic and holozoic nutrition.


Answer 45:
(a) X is solar energy and Y is chemical energy.
(b) The various steps involved in the process of photosynthesis are:-
Absorption of solar energy by the chlorophyll
Splitting of water into hydrogen and oxygen by this light energy
Conversion of solar energy into chemical energy
Reduction of carbon dioxide to form glucose by the transformed chemical energy


Answer 46:
(a) Plants prepare their own food in the presence of sunlight and chlorophyll. This is done by converting simple inorganic materials like carbon dioxide and water present in the surroundings.
(b) Plants need nitrogen for making proteins and other compounds. Plants obtain nitrogen from the soil.


Answer 47:
(i) The mode of nutrition in which the organisms depend upon dead and decaying plants, animals and organic materials for obtaining their nutrition is known as saprophytic nutrition. Example: Fungi
(ii) The mode of nutrition in which an organism derives its nutrition from the body of other living organisms is known as parasitic nutrition. Example: Cuscuta
(iii) The mode of nutrition in which an organism takes in the complex organic food material into its body by the process of ingestion, followed by digestion and then absorption of food in the body cells is known as holozoic nutrition. Example: Human beings


Answer 48:
(i) Organisms that obtain their nutrition from dead and decaying plants, animals or organic matter are known as saprophytes. Two saprophytes are mushroom and bread mould.
(ii) Organisms that feed on other living organisms, called hosts, are known as parasites.
Two parasites are Cuscuta and Plasmodium.


Answer 49:
(a) Carbon dioxide from the air enters the leaves of a plant through tiny pores present on the lower surface of the leaves called stomata.
(b) Water is absorbed from the soil by the root hairs present in the roots of the plants through the process of osmosis.


Answer 50:
The gastric juice contains hydrochloric acid, pepsin enzyme and mucus. Their functions are as follows:-
1) Hydrochloric acid: It creates an acidic environment for the action of pepsin as well as kills the bacteria present in the food.
2) Pepsin: It begins the digestion of proteins into smaller molecules.
3) Mucus: It protects the stomach wall from hydrochloric acid.


Answer 51:
Pancreatic juice contains digestive enzymes such as amylase, trypsin and lipase.
Following are the functions of these substances:
(a) Amylase breaks down the starch.
(b) Trypsin digests the proteins.
(c) Lipase breaks down the emulsified fats.


Answer 52:
(a) In our stomach, the role of hydrochloric acid is to create an acidic condition by making the gastric juice acidic.
(b) The function of enzymes in the human digestive system is to digest the complex food substances like starch, proteins and fats into simple molecules.


Answer 53:
(a) Bile is secreted by liver. It is stored in the gall bladder and helps in the digestion of fats. Also, it converts the acidic food into alkaline.
(b) Trypsin is an enzyme present in the digestive juice secreted by the pancreas. Its function is to digest the proteins.


Answer 53:
(a) Bile is secreted by liver. It is stored in the gall bladder and helps in the digestion of fats. Also, it converts the acidic food into alkaline.
(b) Trypsin is an enzyme present in the digestive juice secreted by the pancreas. Its function is to digest the proteins.


Answer 55:

Column I Column II
(i) Leech (c) Parasitic nutrition
(ii) Amoeba (a) Holozoic nutrition
(iii) Mushroom (d) Saprophytic nutrition
(iv) Green plant (b) Autotrophic nutrition

Answer 56:
(a) Photosynthesis is the process in plants that converts light energy into chemical energy.
(b) Heterotrophs cannot prepare their own food.
(c) Autotrophs can prepare their own food.
(d) Chloroplast is the cell organelle where photosynthesis takes place.
(e) Guard cells surround a stomatal pore.
(f) Pepsin is an enzyme secreted by the gastric glands in the stomach. It acts on proteins.


Answer 57:

Column I Column II
(i) Trypsin (c) Pancreas
(ii) Amylase (d) Saliva
(iii) Bile (a) Liver
(iv) Pepsin (b) Gastric glands

Exercise : Solution of Questions on page Number :26


Answer 58:
(a) In Cuscuta, ticks and leeches, the mode of nutrition is parasitic.
(b) (i) Trypsin acts on proteins.
(ii) Amylase acts on starch.
(iii) Pepsin acts on proteins.
(iv) Lipase acts on emulsified fat.
(c) Absorption of digested food occurs mainly in the small intestine because it consist of many finger-like projections called villi that are supplied with numerous blood vessels. They provide a large surface area for the absorption of food.


Answer 59:
(a) Herbivores depend on plants for their nutrition. These plants contain complex carbohydrates like cellulose and hemicellulose that need to be broken down, whereas carnivores do not eat plants. Hence, small intestine is longer in herbivores than in carnivores.
(b) Mucus protects the stomach wall from hydrochloric acid. If mucus is not secreted by the gastric glands then the stomach wall will be destroyed by the acid.
(c) Peristalsis causes the movement of food inside the alimentary canal.


Answer 60:
(a) When water flows into the guard cells, they swell and become curved. This causes the stomatal pore to open. On the other hand, when the guard cells lose water, they shrink and this cause the pore to close.
(b) The plant kept in continuous light will live longer as the leaves of the plants will be able to make food for the plant through photosynthesis. However, in the absence of light, the leaves will not be able to make food. This is because photosynthesis will not take place in the absence of light. Hence, the plant kept in dark will live shorter as compared to the plant kept in light.


Answer 61:
(a) Green plants provide food and oxygen to all other living organisms. If they disappear from the Earth, all other organisms will die due to starvation and lack of oxygen for respiration.
(b) No, it does not mean that photosynthesis is not taking place. During the day, carbon dioxide released by plants during respiration is used up for photosynthesis, and some of the oxygen released during photosynthesis is used for respiration by the plants. Release of oxygen is a sign that photosynthesis is occurring in plant.


Answer 62:
(a) If leaves of a healthy potted plant were coated with vaseline, it will not remain healthy for long. Due to the coating of vaseline, the stomatal pores will be blocked. Hence, the plant will not be able to get oxygen for respiration and carbon dioxide for photosynthesis. Transpiration will also stop and the plant will ultimately die.
(b) The rate of photosynthesis will:
(i) first decrease as there will be less sunlight and then increase during the afternoon
(ii) decrease due to less availability of water
(iii) decrease due to the closed stomatal pores


Answer 63:
(a) The process by which green plants use sunlight to make their own food from carbon dioxide and water is known as photosynthesis. This is done in the presence of chlorophyll.
(b)Following chemical equation shows the process of photosynthesis in plants:
6CO2 + 6H2O →In the presence of sunlightChlorophyll C6H12O6 + 6O2
Carbon dioxide Water Glucose Oxygen
(c) In green plants, stomatal pores of the leaves absorb carbon dioxide from the air. Chlorophyll present in the plant cells absorbs sunlight and root hair absorbs water from the soil. All these reach chlorophyll, which utilises the Sun’s energy to combine water and carbon dioxide to form glucose and oxygen. In this way, green plants convert solar energy into chemical energy by forming carbohydrates.


Answer 64:
(a) The raw materials required for photosynthesis are water and carbon dioxide. Plants obtain water from the soil through roots and carbon dioxide from the atmosphere through stomata.
(b) Following are the conditions necessary for photosynthesis:
Sunlight
Chlorophyll
Carbon dioxide
Water
(c) Following are the factors that affect the rate of photosynthesis:
Appropriate sunlight
Water availability
Availability of carbon dioxide


Answer 65:
(a) The process of intake and utilisation of nutrients like carbohydrates, proteins, vitamins and fats by an organism is known as nutrition. Nutrition is necessary for an organism because it provides it with the appropriate amount of nutrients that are needed for the maintenance of life and survival of organisms.
(b) Following are the different modes of nutrition:
(i) Autotrophic nutrition:
It is the mode of nutrition in which an organism makes its own food by the process of photosynthesis. Green plants are autotrophs.
(ii) Heterotrophic nutrition:
It is the mode of nutrition in which an organism obtains its food from the autotrophs or other heterotrophs. All animals are heterotrophs.
(c) The mode of nutrition in a (i) roundworm and a (ii) Plasmodium is parasitic.


Answer 66:
(a) Animals that eat plants for their nutrition are called herbivores. For example: Cows and goats
Animals that eat flesh of other animals are called carnivores. For example: Lions and tigers
Animals that eat both plants and animals are called omnivores. For example: Human beings and bears
(b) Goats, elephants, rabbits and deer are herbivores.
Lions, snakes and hawks are carnivores.
Men, crows and dogs are omnivores.
(c) Following are the five steps that occur in the process of nutrition in animals:
Ingestion
Digestion
Absorption
Assimilation
Egestion


Answer 67:
(a) Following are the steps involved in the nutrition in Amoeba:
(i) Ingestion: Amoeba ingests food along with a little amount of the surrounding water. It does this using its pseudopodia and forms a food vacuole.
(ii) Digestion: The food in the food vacuole is digested by the digestive enzymes that enter from the cytoplasm.
(iii) Absorption: The digested food is directly absorbed in the cytoplasm of the Amoeba cell by diffusion.
(iv) Assimilation: Some part of the digested food is used for acquiring energy for various life processes. This is done through respiration.
(v) Egestion: The undigested food is thrown out of the body through the cell membrane.

(b) An Amoeba has holozoic mode of nutrition.
(c) The process of obtaining food by Amoeba is called phagocytosis. It means cell feeding.


Answer 68:

(a)


Following is the process of digestion of food in a human being:
(i) Digestion in mouth: Digestion of food starts in the mouth. Here, the food is cut into small pieces by the teeth. The saliva produced by the salivary glands is mixed with the food by the tongue. The saliva contains the enzyme salivary amylase, which digests the starch and breaks it into sugar.
(ii) Digestion in stomach: The food then passes through the oesophagus and reaches the stomach. The walls of stomach release hydrochloric acid, mucous and the enzyme pepsin. HCl creates an acidic environment in the stomach, pepsin digests proteins and mucous prevents the stomach wall from erosion.
(iii) Digestion in small intestine: The partially digested food enters the small intestine. Small intestine receives secretions from liver and pancreas. Liver secrets bile, which helps in making the food alkaline and also breaks the fats. Pancreas secrete three enzymes, which are trypsin, amylase and lipase. Trypsin digests proteins, amylase digests starch and lipase digests fats.
The intestinal juice secreted by small intestine completes the digestion of starch into glucose, proteins into amino acids and fats into fatty acid and glycerol.
(b) Small intestine has many tiny finger like projections in their inner walls, which are called villi. These increase the surface area for rapid absorption of the digested food, making the small intestine well-adapted for absorption.
(c) Peristalsis is the special name of the contraction and expansion movement that pushes the food further into our digestive tract (or alimentary canal).


Answer 69:
(a)

Our tooth contains the following three parts:
(i) Enamel: It is the outer covering of the teeth. It is harder than bones. In fact, it is the hardest material in the human body.
(ii) Dentine: It is located below the enamel. It is similar to bones.
(iii) Tooth pulp: It is a pulp cavity that consists of nerves and blood vessels. It is located inside the dentine.
(b) The formation of small cavities in the teeth are known as dental caries. They are caused by acids formed by bacteria on eating sugar laden food. It is also caused by improper dental care.
(c) Dental plaque refers to a sticky, yellowish layer of food particles and bacterial cells that deposits on the teeth if they are not cleaned regularly. Dental plaque leads to tooth decay. Brushing of teeth regularly after eating food prevents the formation of plaque.


Answer 70:
(a) The main organs of human digestive system are mouth, oesophagus, stomach, small intestine, large intestine and anus. The associated glands are salivary glands, liver and pancreas.
(b) Carbohydrates are digested by the enzyme, salivary amylase, present in the saliva. As food enters the mouth cavity, it gets mixed with the saliva, which contains salivary amylase. This enzyme helps in the digestion of starch.
The enzyme, pancreatic amylase, is secreted by the pancreas. This enzyme reaches the small intestine and digests the carbohydrates.
Proteins are digested by the enzyme, pepsin, that is secreted in the stomach by the glands presents in its walls. Trypsin is secreted by the pancreas. This enzyme reaches the small intestine and digests the proteins.
Fats are digested by the enzyme, lipase, that is secreted by the pancreas and the bile juice that is secreted by the liver. These two act on the fats in the small intestine.


Exercise : Solution of Questions on page Number :27


Answer 71:
(c) herbivore
This is because herbivores mainly eat plants.
Plants contain cellulose, which is difficult to digest. Hence, they have the longest small intestine.


Answer 72:
(c) phagocytosis
Amoebae obtain food by the process called phagocytosis, which means cell feeding.


Answer 73:
(b) Plasmodium
Plasmodium is a microbial parasite that has a parasitic mode of nutrition.


Answer 74:
(a) mushroom
Mushroom obtains its food from decaying organic materials like rotten wood. Thus, it has a saprophytic mode of nutrition.


Answer 75:
(d) 6.5 m
The length of small intestine in a human adult is around 6.5 m.


Answer 76:
(c) mouth
The process of digestion begins in the mouth with the help of the enzymes present in the saliva.


Answer 77:
(b) small intestine
The digestion of food, i.e. carbohydrates, fats and proteins, completes in the small intestine.


Answer 78:
(b) Liver
Liver secretes the greenish yellow liquid called bile.


Answer 79:
(c) Parakeet and Paramecium
Parakeet and Paramecium feed on solid food. Therefore, they have holozoic mode of nutrition.


Answer 80:
(d) All of the above
In autotrophic mode of nutrition, green plants that have chlorophyll, make food from carbon dioxide and water in the presence of sunlight.


Answer 81:
(c) Ingestion → Digestion → Absorption → Assimilation → Egestion
The food is ingested through the mouth. It is then digested in the mouth, the stomach and the small intestine. Then, it is absorbed and assimilated in the small intestine, the reabsorption of water takes place in the large intestine and the undigested waste is egested through the anus.


Answer 82:
(d) stomach and pancreas
Pepsin is secreted by the stomach and trypsin is secreted by the pancreas.


Answer 83:
(c) to remove the chlorophyll
When carrying out the starch test, it is important to remove the chlorophyll by boiling the leaf in alcohol. This is done because the green colour of the chlorophyll interferes with the iodine test.


Answer 84:
(d) proteins, fats and carbohydrates
Pancreatic juice has the enzymes amylase for the digestion of carbohydrates, trypsin for the digestion of proteins and lipase for the digestion of emulsified fats.


Answer 85:
(d) secreted by liver and stored in gall bladder
Bile is secreted by the liver and stored in the gall bladder till required.


Answer 86:
(d) stomach
The digestion of proteins begins in the stomach by pepsin.


Answer 87:
(b) mucus
Mucus protects the inner lining of the stomach from erosion, which can be caused by hydrochloric acid.


Answer 88:
(b) small intestine
Small intestine receives bile from the liver, which is temporarily stored in the gall bladder.


Answer 89:
(d) carbohydrate
Carbohydrates are digested by amylases that are present in the saliva and the pancreatic juice.


Exercise : Solution of Questions on page Number :28


Answer 90:
(b) starch breaking down into sugars
Salivary amylase digests carbohydrates. Starch is a carbohydrate, which is digested and broken down into sugars by the salivary amylase in the buccal cavity.


Answer 91:
(d) trypsin digests proteins and lipase emulsified fats
Trypsin and lipase are enzymes present in the pancreatic juice that digest proteins and emulsified fats, respectively.


Answer 92:
(b) water
During photosynthesis, the water molecule is split into hydrogen and oxygen.


Answer 93:
(c) movement of molecules does not take place among cells
Movement of molecules takes place among cells.


Answer 94:
(d) Starch
The autotrophs, like plants, store energy in the form of starch.


Answer 95:
(c) oxidation of carbon to carbon dioxide
Photosynthesis involves the conversion of light energy into chemical energy by chlorophyll. In this process, carbon dioxide is reduced to carbohydrates.


Answer 96:
(b) water in guard cells
When guard cells have water, stomatal pores open and when water moves out of the guard cells, these pores close.


Answer 97:
(b) nitrates and nitrites
Plants cannot absorb atmospheric nitrogen. Plants can uptake nitrogen in the form of nitrates and nitrites only.


Answer 98:
(c) amylase
The digestion of food begins in the mouth by the action of salivary amylase.


Answer 99:
(c) Heterotrophs do not synthesise their own food.
Heterotrophs cannot synthesis their food.


Answer 100:
(b) Yeast, Mushroom, Bread mould
Fungi (yeast, mushroom, bread mould) are saprophytes. They obtain their food by breaking it outside the body and then absorbing it.


Answer 101:
d) Mouth → Oesophagus → Stomach → Small intestine → Large intestine
The correct sequence of the parts as they occur in the human alimentary canal is given below.
Mouth → Oesophagus → Stomach → Small intestine → Large intestine


Answer 102:
(a) (i) Organism A is bacteria and (ii) substance B is acid.
(b) (i) Part C is the tooth enamel and (ii) part D is the dentine of the tooth.
(c) The small holes, E, are known as cavities.
(d) F is the pulp of the tooth.
(e) When bacteria (organism A) reaches the pulp (part F) of the tooth, it irritates the nerve endings and causes toothache.


Exercise : Solution of Questions on page Number :29


Answer 103:
(a) W is the dental plaque.
(b) (i) X refers to the saliva, while (ii) Y refers to the salivary glands.
(c) Organisms Z are bacteria.
(c) Layer of W, i.e. dental plaque, can be removed by regular brushing of teeth.


Answer 104:
(a) (i) Gland A is salivary gland.
(ii) Substance B is saliva.
(iii) Enzyme C is salivary amylase.
(b) Tube D is oesophagus.
(c) The movement E is known as peristaltic movement.
(d) (i) F is hydrochloric acid, (ii) G is mucus and (iii) H is pepsin.


Answer 105:
(a) The organ A is small intestine.
(b) (i) Liquid B is bile and (ii) organ C is gall bladder.
(c) The digestive enzymes D, E and F are amylase, trypsin and lipase, respectively.
(d) The projections G are villi that are present on the inner wall of organ A.
(e) (i) Tube H is the large intestine, (ii) part I is the rectum, (iii) opening J is the anus and (iv) the process K is egestion or defecation.


Answer 106:
(a) The unicellular animal P is Amoeba.
(b) (i) Q is pseudopodia and (ii) R is the food vacuole.
(c) (i) Chemical S is the digestive enzyme and (ii) process T is diffusion.
(d) (i) Organelle U is cell membrane and (ii) process V is egestion.


Answer 107:
(a) (i) Organism B refers to an omnivore, (ii) organism D refers to a herbivore and (iii) organism A refers to a carnivore.
(b) Organism C is an autotroph.
(c) The organisms A, B and D are heterotrophs as they obtain food from other organisms and cannot synthesise their own food.
(d) Organism C can be a producer as it is an autotroph.
(e) The organisms A, B and D are consumers as they all are heterotrophs.
(f) The examples of organisms A, B, C and D are lion, crow, green plants (like mango) and cow, respectively.


Exercise : Solution of Questions on page Number :30


Answer 108:
(a) (i) Organism A has parasitic mode of nutrition, (ii) organism B has holozoic mode of nutrition and (iii) organism C has saprophytic mode of nutrition.
(b) The organisms like D are called hosts.
(c) The process E is egestion.
(d) The example of organisms like (i) A is Cuscuta, (ii) B is cow and (iii) C is mushroom.
(e) The general name of the three modes of nutrition exhibited by organism A, B and C are parasitic nutrition, holozoic nutrition and saprophytic nutrition, respectively.


Answer 109:
(a) (i) Organism A is a green plant, (ii) food B is glucose and (iii) food H is starch.
(b) C is carbon dioxide and D is water.
(c) (i) The green coloured substance E is chlorophyll and (ii) organ F is a leaf.
(d) The process G is photosynthesis.


Answer 110:
(a) Animals like X are known as carnivores.
(b) Animals like Y are known as herbivores.
(c) Animals like X have longer small intestine as they are grass eating animals and they need long intestine to digest the cellulose present in the grass.
(d) Lion is a carnivore.
(e) Cow is a herbivore.


Exercise : Solution of Questions on page Number :46


Answer 1:
No, all cells do not use oxygen to produce energy. Cells can also produce energy by anaerobic respiration, where oxygen is not required.


Answer 2:
Ethanol is produced as the result of the breakdown of pyruvate during anaerobic respiration, not in aerobic respiration.


Answer 3:
Yeast can live without oxygen as it can respire anaerobically.


Answer 4:
In aerobic respiration, more energy is released because there is complete breakdown of food.


Answer 5:
Lactic acid, which is formed in muscles during vigorous physical exercise, may cause cramps.


Answer 6:
Root hair is involved in the exchange of respiratory gases as they are in direct contact with the air present in the soil.


Exercise : Solution of Questions on page Number :47


Answer 7:
All the plant parts like roots, stems and leaves get oxygen by passive diffusion, which is required for respiration.


Answer 8:
Stomata are the pores present on the surface of the leaves through which exchange of gases takes place.


Answer 9:
The outer covering of the woody stems, which is known as the bark, has lenticels through which respiratory exchange of gases takes place.


Answer 10:
Root hair is the extension of the epidermal cells of a root, which help in respiration.


Answer 11:
(a) Respiration occurs all the time.
(b) Photosynthesis occurs only at daytime as it can take place only in the presence of sunlight.


Answer 12:
In fish, gills are the organs of breathing.


Answer 13:
Earthworms absorb oxygen through their moist skin.


Answer 14:
Amoeba depends on simple diffusion of gases for breathing.


Answer 15:
Aquatic animals like fishes, prawns and mussels breath through gills.


Answer 16:
The trachea divides into two tubes at its lower end, which are known as bronchi.


Answer 17:
Blood absorbs oxygen in the lungs. The exchange of gases takes place in the alveoli of lungs and the blood present in the blood capillaries surrounding the alveoli.


Answer 18:
Haemoglobin is the red pigment that is present in red blood cells. It carries oxygen in the blood.


Answer 19:
Carbon dioxide and oxygen are exchanged in the lungs. Oxygen from the inhaled air is exchanged for carbon dioxide present in the blood.


Answer 20:
Gas exchange takes place in the alveoli of the lungs.


Answer 21:
Alveoli are the tiny air-sacs at the end of smallest bronchioles in the lungs.


Answer 22:
Wind-pipe is also known as trachea.


Answer 23:
The two lungs are attached to the two bronchi.


Answer 24:
(a) Oxygen is taken into the body
(b) Carbon dioxide is removed from the body.


Answer 25:
(a) False
During respiration, the plants take oxygen and release carbon dioxide.
(b) True
Energy can be produced in the cells even without oxygen.
(c) False
Fish breathe through gills and earthworms breathe through their moist skin.


Answer 26:
(a) The organs of respiration in man are the lungs.
(b) The actual exchange of gases takes place in the alveoli of the lungs.
(c) Alveoli in the lungs provide a very large surface area for gaseous exchange.
(d) Yeast undergoes anaerobic respiration, whereas Amoeba undergoes aerobic respiration.
(e) Gills are the breathing organs in aquatic animals (fish).


Answer 27:
The roots of plant can not respire if they remain water logged for a long time. This is because water replaces the air present between the soil particles. Thus, the roots do not get enough air to respire and the plant may die.


Answer 28:

Aerobic respiration  Anaerobic respiration
It occurs in the presence of oxygen. It occurs in the absence of oxygen.
Here, complete breakdown of food occurs. Here, partial breakdown of food occurs.
Here, the end products are carbon dioxide and water. Here, the end products are ethanol and carbon dioxide (as in yeast) or lactic acid (as in animal muscles)
.It releases a large amount of energy.  It produces less amount of energy.

The organisms that use anaerobic mode of respiration include some bacteria and microorganisms such as yeast.


Answer 29:
(a) During anaerobic respiration in plants (like yeast), ethanol, carbon dioxide and energy are the final products.
(b) During anaerobic respiration in an animal tissue (like muscles), lactic acid and energy are the final products.


Answer 30:
Anaerobic respiration takes place in human muscles during vigorous physical exercise. This is because oxygen gets used up at a faster rate in the muscle cells than can be supplied by the blood-carrying oxygen.


Answer 31:
(a) In the anaerobic respiration that takes place in yeast, the end products are C2H5OH and CO2.
(b) In the aerobic respiration that takes place in human cells in the presence of oxygen, the end products are CO2 and H2O.
(c) In the anaerobic respiration that takes place in animal tissues like muscle cells, the end product is lactic acid.


Answer 32:

Breathing Respiration
It is a physical process. It is a biochemical process.
t involves exchange of gases. It involves exchange of gases along with the oxidation of food.
It involves the lungs, where the exchange of gases takes place. Along with the lungs, it involves the mitochondria of the cells, where oxidation of food takes place.

Answer 33:
Glucose is oxidised in two ways to provide energy.
(a) Aerobic respiration: Glucose is completely oxidised to carbon dioxide and water in the presence of oxygen, with the release of a considerable amount of energy. This type of oxidation occurs in most of the living organisms such as human beings, birds, snakes, frogs, fish, etc.
(b) Anaerobic respiration: This type of respiration occurs in the absence of oxygen. In this type of oxidation, glucose is partially oxidised to ethanol and carbon dioxide (yeast and other bacteria) or lactic acid (muscles during physical exercise and some bacteria) with the release of a small amount of energy.


Exercise : Solution of Questions on page Number :48


Answer: 34
When air is taken in and let out during breathing, the lungs always contain a residual amount of air. This is because there is sufficient time for the oxygen to be absorbed into the blood and for the carbon dioxide to be released from the blood.


Answer: 35
Carbon monoxide combines with haemoglobin and forms carboxyhaemoglobin by replacing the oxygen. This reduces the oxygen carrying capacity of the blood. Due to the lack of oxygen, the person cannot breathe properly. In extreme cases, a person may even die due to oxygen starvation. Hence, it is dangerous to inhale the air containing carbon monoxide.


Answer: 36
Ameoba is a unicellular organism. It depends on simple diffusion of gases for breathing. The exchange of gases in Amoeba takes place through its cell membrane. Since it lives in water, the oxygen from water diffuses into the body of Amoeba through its cell membrane. This oxygen is used for respiration inside the Amoeba cell. The process of respiration continuously produces carbon dioxide that diffuses out through the membrane of Amoeba into the surrounding water. Respiration in Amoeba is aerobic.


Answer: 37
All the respiratory organs like skin, gills and lungs have three common features.(a) They have a large surface area to get enough oxygen.(b) They have thin walls for easy diffusion and exchange of respiratory gases.(c) They have a rich blood supply for transporting respiratory gases.


Answer: 38
Fish have special organs for breathing. They are called gills. For breathing, the fish use the oxygen dissolved in water. They breathe by taking in water through their mouth and sending it over the gills. When water passes over the gills, the dissolved oxygen is extracted. The water then goes out through the gill slits. The extracted oxygen is absorbed by the blood and carried to all the parts of the body. The carbon dioxide produced during respiration is brought back by the blood into the gills for expelling into the surrounding water. The gaseous exchange in fish takes place in the gills.


Answer: 39
The deficiency of haemoglobin in our bodies would reduce the oxygen carrying capacity of the blood, resulting in breathing problems, tiredness and lack of energy. Due to this, we would look pale and lose weight.


Answer: 40
(a) The respiration in roots takes place by the diffusion of respiratory gases through the root hair. The root hair take the oxygen required for respiration from the air present in-between the soil particles, by the process of diffusion. The oxygen reaches all the other cells of the root for respiration. During respiration, the carbon dioxide gas produced in the cells of the root  moves out through the same root hair by the process of diffusion.
(b) The stems of herbaceous plants have stomata. The oxygen from air diffuses into the stem of a herbaceous plant through stomata and reaches all the cells, for respiration. The carbon dioxide gas produced during respiration diffuses out into the air, through the same stomata. In woody stems, the bark has lenticels for gaseous exchange.
(c) ​The leaves of a plant have tiny pores called stomata. The oxygen from air diffuses into a leaf through stomata and reaches all the cells, where it is used in respiration. The carbon dioxide gas that is produced during respiration, diffuses out from the leaf into the air through the same stomata.


Answer: 41
(a) Terrestrial animals live on land. They respire through lungs. Examples of terrestrial animals are human beings, cows, cats, dogs, etc.Aquatic animals live in water. They have a special organ for respiration. They are called gills. An example of aquatic animals is fish.(b) Aquatic animals obtain the oxygen dissolved in water for breathing and respiration. Terrestrial animals obtain oxygen present in air for breathing and respiration.


Answer: 42
Fish do not have lungs that can utilise the oxygen of the air for breathing and respiration. The fish have gills. Gills can only extract the dissolved oxygen from water and provide it to the fish. Gills cannot take in the oxygen from the air. Since fish do not get oxygen for breathing when taken out of water, they die.


 Answer: 43
The aquatic organisms use the oxygen dissolved in water to carry out respiration. Since the amount of dissolved oxygen in water is low as compared to the amount of oxygen in air, the rate of breathing in aquatic animals is much faster than in terrestrial animals.


Answer: 44
The energy currency in the living organisms is adenosine triphosphate (ATP). It is produced in the mitochondria, during respiration.


Answer: 45
Plants do not need to move from one place to another. Movements in a plant is usually at the cellular level. Thus, a far less amount of energy is required by the plants. Animals, on the other hand, need to move from one place to another in search of food. So, the energy need of animals is much higher than plants.


Answer: 46
If humans also had gills, the deep sea divers would not have to carry oxygen cylinders with them for breathing under the water.


Answer: 47
(a) The main function of the respiratory system is to breathe in oxygen for respiration and to breathe out carbon dioxide, and to provide energy to the body by the breaking down the food particles.
(b) The major organs of respiratory system in a human being are nose, nasal passage, trachea, bronchi, lungs and diaphragm.
(c) Human Respiratory System:


Answer: 48
(a) The nasal passage is lined with fine hair and mucus. When air passes through the nasal passage, the dust particles and other impurities present in it are trapped by the nasal hair and mucus. Due to this, only clean air reaches the lungs.
(b) The walls of trachea do not collapse when there is less air in it because trachea is supported by rings of soft bones called cartilage.
(c) Gaseous exchange in our body takes place in the alveoli of lungs. The oxygen of air diffuses out from the alveoli walls into the blood. As the blood passes through the tissues of the body, the oxygen present in it diffuses into the cells. This oxygen combines with the digested food present in the cells, to release energy. Carbon dioxide gas, which is produced as a waste product during respiration in the cells of the body tissues, diffuses into the blood. Blood carries the carbon dioxide back to the lungs, where it diffuses into the alveoli.
(d) The human lungs have been designed to maximise the exchange of gases.There are millions of alveoli in the lungs. The presence of millions of alveoli in the lungs provide a very large area for the exchange of gases. The availability of large surface area maximises the exchange of gases.


Answer: 49

(a)

 Respiration in plants Respiration in animals
All the parts of a plant perform respiration individually. An animal performs respiration as a single unit.
There is little transport of respiratory gases from one part of the plant to the other. Respiratory gases are usually transported over long distances inside an animal.
 The respiration in plants occurs at a slow rate. The respiration in animals occurs at a much faster rate.

(b) (a) During daytime, the leaves use some of the oxygen produced through photosynthesis for respiration. For photosynthesis, the leaves not only use the carbon dioxide produced through respiration, but some carbon dioxide is also taken in from the air.Thus, during daytime, oxygen diffuses out and carbon dioxide diffuses in.
(b) At night, as photosynthesis does not takes place, oxygen is not produced. Thus, oxygen from air diffuses into the leaves to carry out respiration. And carbon dioxide produced by respiration diffuses out into the air. So, at night, oxygen diffuses in and carbon dioxide diffuses out.
(c) Exhaled air contains more carbon dioxide because we exhale to remove the waste product, i.e. carbon dioxide, from our body.


Answer: 50
(a) Respiration is a vital function of the body because it provides energy for carrying out all the life processes that are necessary to keep the organisms alive. Most living things need oxygen to obtain energy from food. This oxygen reacts with the food molecules present in the body cells and burns them slowly to release energy. This energy is stored as ATP molecules in the cells. The process of releasing energy from food is called respiration.
(b)Aerobic Respiration Anaerobic RespirationIt takes place in the presence of oxygen. It takes place in the absence of oxygen.Complete breakdown of food occurs in aerobic respiration. Partial breakdown of food occurs in anaerobic respiration.The end products are carbon dioxide and water. The end products may be ethanol and carbon dioxide (as in yeast cells) or lactic acid (as in muscle cells).It produces a considerable amount of energy. Much less energy is produced in anaerobic respiration.(c) (i) Anaerobic respiration takes place in yeast.(ii) Aerobic respiration takes place in humans.


Answer: 51
(a) In small unicellular animals, such as Amoeba, the volume of their body is so small that oxygen can be introduced quickly into the whole body by the process of diffusion. This is because the cell of Amoeba is so small that the oxygen does not have to go far. But in case of large multicellular animals like humans, the volume of the body is so big that oxygen cannot quickly diffuse into all the cells of the body. This is because in these cases, the oxygen has to travel a very large distance to reach each and every cell of the body.
(b) In large animals, there is a blood circulatory system to quickly carry the oxygen to all the parts of the body.
(c) A terrestrial animal is surrounded by an oxygen-rich atmosphere from where it can take any amount of oxygen. An aquatic animal uses the oxygen dissolved in water to carry out respiration. The amount of oxygen dissolved in water is low as compared to the amount of oxygen in the air.


Answer: 52
(b) H2OAnaerobic respiration occurs in absence of oxygen. One molecule of glucose breaks down to release two molecules of ethanol, two molecules of carbon dioxide and two ATP molecules.


Answer: 53
(c) YeastYeast can live without the oxygen present in the air. This is because it obtains energy by the process of anaerobic respiration.


Answer: 54
(b) alveoliAlveoli are the pouch-like air sacs at the end of the small bronchioles. The walls of alveoli are very thin. Also, they are surrounded by very thin blood capillaries. It is in the alveoli that the gaseous exchange takes place.


Answer: 55
(a) Electric eelElectric eel respires through gills. Leech and earthworm respire through their skin.


Exercise : Solution of Questions on page Number : 49


Answer: 56
(b) No No There are two pathways through which anaerobic respiration occurs.  In micro-organisms such as yeast and bacteria, the glucose is broken down into ethanol and carbon dioxide, and releases very little energy. In the other pathway, glucose is broken down into only lactic acid with the release of little energy. This occurs in the muscles during strenuous exercise. Therefore, carbon dioxide is not always produced during anaerobic respiration.


Answer: 57
(c) lactic acidIn the muscle cells that lack oxygen, concentration of lactic acid is increased. This is because, here, anaerobic respiration takes place in which glucose is converted into lactic acid with the release of a small amount of energy.


Answer: 58
(b) the oxidation of food substances to release energyInternal respiration may be defined as the oxidation of food substances to release energy.


Answer: 59
(b) carbon dioxideLime water turns milky due to the presence of carbon dioxide in the exhaled air.


Answer: 60
(d) nostrils → pharynx → larynx → trachea → alveoli
The correct sequence of air passage during inhalation is as follows:Nostrils → Nasal chambers → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli


Answer: 61
(d) lactic acidLack of oxygen in muscles causes accumulation of lactic acid, due to anaerobic respiration. Accumulation of lactic acid leads to cramps in the legs of sprinters.
Answer: 62
(c) mitochondriaDuring anaerobic respiration in human beings, pyruvic acid is converted into lactic acid in the mitochondria of the muscle cells.


Answer: 63
(c) (i) and (iv)Statements (i) and (iv) are correct. The explanation for wrong statements are as follows:(ii) Fermentation takes place in the case of anaerobic bacteria.(iii) Fermentation takes place in cytoplasm.


Answer: 64
(d) (ii) and (iv)Statements (ii) and (iv) are correct. The explanation for incorrect statements is given below:(i) During inhalation, ribs move outward and diaphragm moves downward.(iii) Haemoglobin has greater affinity for carbon monoxide than oxygen.


Answer: 65
(c) ATPIn biology, ATP is known as the energy currency of a cell. It is a high energy molecule that stores the energy.Answer: 66
(c) leech and earthwormLeech and earthworm breathe only through their moist skin. Fish breathe through gills, while frogs breathe through lungs and skin.


Answer: 67
(b) prawnPrawn is an aquatic animal that respires through gills. Insects such as grasshopper, mosquito and cockroach respire through tracheae.


Answer: 68
(c) carbon dioxideDuring daytime, the carbon dioxide produced through respiration is used up in photosynthesis by leaves. In fact, more carbon dioxide is taken in from the air for this purpose.So, oxygen is diffused out and carbon dioxide is diffused in.
Hence, if a plant is releasing carbon dioxide during the daytime, then photosynthesis is not taking place.


Answer: 69
(b) lenticelsIn woody stems, the bark (outer covering of the stem) has lenticels for gaseous exchange.


Exercise : Solution of Questions on page Number :50


Answer: 70
(b) Prawn
Prawn is an aquatic animal that respires through gills. The gills extract oxygen dissolved in water and take away carbon dioxide from the body.


Answer: 71
(d) lactic acid
During a marathon, most of the energy in our muscles is produced through aerobic respiration, while anaerobic respiration provides some extra energy needed under these conditions. The anaerobic respiration by the muscles brings about partial breakdown of glucose to form lactic acid. The accumulation of lactic acid in the muscles causes muscle cramps.


Answer: 72
(c) spiracles
In insects (such as cockroaches, grasshoppers), the tiny holes called spiracles are present on the body. Air enters the body through these holes.


Answer: 73
(b) fish
Rate of breathing in aquatic animals is much faster than terrestrial animals. This is because a faster rate of breathing provides more oxygen to the aquatic animals.


Answer: 74
(a) Organism B is undergoing aerobic respiration.
(b) Organism A is undergoing anaerobic respiration.
(c) In anaerobic respiration, glucose breaks down to form alcohol and carbon dioxide with the release of small amount of energy. Hence, organism A can convert glucose into alcohol.
(d) Yeast behaves like organism A.
(e) Humans and dogs behave like organism B.


Answer: 75
(a) (i) Organism A is yeast.
(ii) Organism B is Amoeba.
(iii) Organism C is mosquito.

(b) (i) P is alcohol.
(ii) Q is the cell membrane because Amoeba breathes through the cell membrane.
(iii) R is spiracle.
(iv) S is tracheae.
(c) Organisms B and C undergo aerobic respiration.
(v) Organism A, i.e. yeast, undergoes anaerobic respiration.


Answer: 76
(a) T is Amoeba.
(b) Q is frog.
(c) P is fish.
(d) S is grasshopper.
(e) R is earthworm.


Answer: 77
(a) (i) X is yeast.
(ii) Y is ethanol.
(iii) Z is carbon dioxide.
(b) Fermentation is the process of converting sugar into substance Y by the action of X.
(c) Anaerobic respiration is exhibited by X in the above process.


Answer: 78
(a) Yeast shows anaerobic respiration.
(b) Humans show aerobic respiration.
(c) In humans beings, during high muscular activity, the respiration represented by equation (iii) occurs. It occurs in the muscle tissue.
(d) Equation (ii) represents aerobic respiration.
(e) Equation (i) represents anaerobic respiration.
(f) Aerobic respiration, i.e. the reaction represented by equation (ii), produces maximum amount of energy.


Exercise : Solution of Questions on page Number :51


Answer: 79
Here, A, B, C, D, E, F and G refer to the nose, nostrils, trachea, bronchi, lungs, bronchioles and alveoli, respectively.


Answer: 80
(a) Organism X could be a human being. The breathing organs A are lungs.
(b) Organism Y could be a fish. The breathing organs B are gills.
(c) Organism Z could be a frog. The breathing organ C is skin and D are lungs.
(d) (i) Z is an amphibian.
(ii) Y is an aquatic organism.
(iii) X is a terrestrial organism.


Exercise : Solution of Questions on page Number :72


Answer: 1
(a) In a plant, phloem transports the food.
(b) In a plant, xylem transports water and minerals.


Answer: 2
(a) Xylem vessels and tracheids transport water in plants.
(b) Sieve tubes transport food in the plants.


Answer: 3
In the circulatory system, heart acts as a pump to push out blood.


Answer: 4
(a) Arteries carry blood away from the heart.
(b) Veins carry blood back to the heart.


Answer: 5
The blood absorbs oxygen in the lungs.


Answer: 6
The valves present in the right and the left atrium prevent the blood from flowing backwards into the atria.


Answer: 7
(a) The largest artery in our body is aorta.
(b) The largest vein in our body is vena cava.


Answer: 8
Carbon dioxide, water vapour and oxygen are the main gaseous waste products excreted by plants.


Answer: 9
In our body, the dirty blood is filtered in the kidneys.


Answer: 10
Dialysis is the procedure used in the working of artificial kidney.


Answer: 11
Blood includes the other four terms. This is because plasma, platelets, RBC and WBC are the components of blood.


Answer: 12
Xylem and phloem are the two main components of the transport system in the highly organised plants.


Answer: 13
(a) Phloem carries materials both upwards as well as downwards.
(b) Xylem carries materials only upwards.


Exercise : Solution of Questions on page Number :73


Answer: 30
Xylem is a conducting tissue in plants. It transports water and minerals, which are absorbed from the soil by the roots of the plants, to various parts of the plant such as stems, leaves and flowers.
The two kinds of cells in xylem tissue are xylem vessels and tracheids. Both of these cells are dead cells.


Answer: 31
Phloem is a conducting tissue in plants. It transports the food made in the leaves to all the parts of the plant like branches, roots and stems.
Phloem contains two types of cells, i.e. sieve tubes and companion cells. Both of these cells are living cells.


Answer: 32
(a) The evaporation of water from the leaves of a plant in the form of water vapour is called transpiration.
(b) The transport of food from the leaves to other parts of the plant is called translocation.
(c) Phloem translocates the food made in the leaves.


Answer: 33
(a) Structure of a xylem vessel

Structure of sieve tube (or phloem)

(b) Difference between transport of materials in xylem and phloem: Transport of materials in xylem Transport of materials in phloemXylem involves the transport of water and minerals from the soil via roots to the rest of the plant body.     Phloem involves transport of food materials from the leaves to different parts of the plant body.Movement of water is unidirectional, i.e. upwards from the roots to the aerial parts of the plant. Movement of food is bidirectional, i.e. both upward and downward.Transport of material in xylem requires physical forces such as transpirational pull.   Transport of material in phloem requires energy in the form of ATP.
Structure of sieve tube (or phloem)

(b) Difference between transport of materials in xylem and phloem:

Transport of materials in xylem Transport of materials in phloem
Xylem involves the transport of water and minerals from the soil via roots to the rest of the plant body. Phloem involves transport of food materials from the leaves to different parts of the plant body.
Movement of water is unidirectional, i.e. upwards from the roots to the aerial parts of the plant. Movement of food is bidirectional, i.e. both upward and downward.
Transport of material in xylem requires physical forces such as transpirational pull. Transport of material in phloem requires energy in the form of ATP.

Answer: 34

Column I Column II(
i) Heart  (c) Pumping organ
(ii) Arteries and Veins (a) Pipes for transport in humans
(iii) Xylem vessels (d) Water transport in plants
(iv) RBC (e) Carrier of oxygen(
 v) Platelets  (b) Clotting of blood

Answer: 35
The process of removing waste products from the body of an organism is called excretion. The excretory unit of the kidney is nephron.


Answer: 36
(a) Kidneys filter the wastes out of the blood and form the urine. They also maintain the water balance of the body.
(b) Kidneys remove the poisonous substance (urea), other waste salts and excess water from the blood, and excrete them in the form of urine.
(c) Ureters are the tubes that connect the kidneys to the bladder.
(d) The urinary bladder stores the urine until it is forced out of the body through an opening known as urethra.


Answer: 37
The major waste products of the cells are nitrogenous wastes like ammonia and urea. Both of these compounds are toxic to the human body and must be removed from the blood regularly. The kidneys remove these wastes from the body. However, if the kidneys fail to function, the waste may accumulate and damage the internal organs of the body, which can even lead to the death of the organism. Therefore, in case of kidney failure, blood must be filtered periodically using a dialysis machine to remove the accumulated wastes from the body.
The dialysis machine cleans the blood of a person by removing the nitrogenous wastes products from it.


Answer: 38
The liquid part of the blood is called plasma. The main function of the platelets is to prevent bleeding. They contain essential chemicals that help in the coagulation of blood.


Answer: 14
In the human body, blood and lymph are two liquids that help in the transport of substances.


Answer: 15
The other name of the main vein is vena cava.


Answer: 16
Phloem is the conducting tissue of plants that is made of the sieve tubes along with the companion cells.


Answer: 17
(a) Phloem is made up of sieve tubes, which are the living cells.
(b) Xylem is made up of xylem vessels and tracheids. Both are non-living conducting tissues, which have thick walls.


Answer: 18
The transport of food from the leaves to other parts of the plant is called translocation.


Answer: 19
ATP is utilised during the loading of food made in the leaves into the sieve tubes of phloem tissue. Thus, it is used in the transport of food.


Answer: 20
Blood circulatory system and lymphatic system are the two types of transport systems in human beings.


Answer: 21
(a) Oxygen is released only during daytime. This is because oxygen is produced by photosynthesis only in the presence of sunlight.
(b) Carbon dioxide is released only during the night because carbon dioxide produced during respiration in completely used up by the plant itself in photosynthesis.


Answer: 22
Human beings have double circulation, while fish have single circulation of blood.


Answer: 23
(a) True
(b) False
The value of diastolic pressure is always lower than that of the systolic pressure.


Answer: 24
The gaseous waste products of a plant are released into the air through the leaves and the stems.


Answer: 25
Glucose is reabsorbed into the blood through the blood capillaries surrounding the tubule.


Answer: 26
The two waste products of the human body are carbon dioxide and urea.


Answer: 27
In the kidney, the function of glomerulus is to filter the blood passing through it.


Answer: 28
High blood pressure is called hypertension.


Answer: 29
(a) Gums and resins are the waste products of plants.
(b) Bowman’s capsule and tubule taken together make a nephron.
(c) The organs which extract the nitrogenous wastes from the blood are kidneys.
(d) The extracellular fluid which always flows from body tissues to the heart is called lymph.
(e) The white blood cells make antibodies whereas red blood cells help in respiration.


Exercise : Solution of Questions on page Number :74


Answer: 39
(a) There are three types of blood vessels in the human body. They are arteries, veins and capillaries.
(b) Heart needs valves to regulate the flow of blood. It allows the blood to flow through the heart only in one direction.


Answer: 40
(i) The tubes, which are selectively permeable membranes, are made up of cellulose.
(ii) The dialysing machine contains water, glucose and salts, which are in similar concentrations to those in normal blood.
(iii) The main waste that passes into the dialysing solution is urea.


Answer: 41
Differences between artery, vein and capillary:

Arteries Veins Capillaries
Arteries are tough, thick and elastic tubes. Veins are thin-walled and non-elastic tubes. Capillaries are very thin-walled tubes.
They have a narrow lumen. They have a wide lumen. They have a very narrow lumen, just wide enough for a red blood cell to pass through it.
They carry blood away from the heart to the various organs of the body, at a high pressure. They transport blood towards the heart from various organs, at a low pressure. They carry blood from the arteries to the veins.
They do not have valves. They have valves to prevent backward flow of the blood. They do not have valves.
They transport only oxygenated blood (except for the pulmonary artery). They transport only deoxygenated blood (except for the pulmonary vein). They exchange oxygen, carbon dioxide, water and salts between the blood and the surrounding tissues.

Answer: 42
(a) The upper parts of the heart are called atria.
(b) The lower parts of the heart are called ventricles.
(c) Capillaries are thin-walled tubes, which connect the arteries to the veins.
(d) (i) Right side of the heart pumps blood into the lungs.
(ii) Left side of the heart pumps blood to the entire body, except the lungs.


Answer: 43
(a) Following are the various methods used by plants to get rid of their waste products.
The gaseous wastes are removed through stomata in leaves and lenticels in stems.
Some wastes are removed in the form of gums and resins.
Some of the waste products are excreted into the soil around them.
(b) Amoeba excretes excess carbon dioxide, water and ammonia. Carbon dioxide is excreted by diffusion through the cell membrane, while excess water and nitrogenous waste like ammonia is removed by the contractile vacuole.


Answer: 44
(a) Lymph is a clear, yellowish, slightly alkaline fluid, containing white blood cells in a liquid that resembles blood plasma.
Functions of lymph:

It helps in the defensive mechanism of the body by killing the foreign body with the help of lymphocytes and making antibodies.
It transports nutrients from the tissue cells to the blood, through lymphatic vessels.
(b) A reading of 120/80 means that the person has a normal blood pressure. Here, the systolic pressure is 120 mm Hg and the diastolic pressure is 80 mm Hg.


Answer: 45
Hypertension is the term used for high blood pressure. It is known as a “silent killer”.
High blood pressure results from the tightening (constriction) of very small arteries called arterioles. Arterioles regulate the blood flow through our body. As these arterioles constrict, the heart has to work harder to pump the blood through the smaller space. Due to this, the pressure inside the vessels grows.
A very high blood pressure can lead to the rupture of artery and internal bleeding.


Answer: 46
Following are the various components of blood:
(a) Plasma: It helps in the transport of food, carbon dioxide, wastes and salts.
(b) Erythrocytes (RBCs): They carry the oxygen from the lungs to all parts of the body.
(c) Leucocytes (WBCs): They fight infections and protect the body from foreign particles, like germs and bacteria.
(d) Platelets: They help in the coagulation of blood by releasing the chemicals that clot blood at the site of injury or wound.


Answer: 47
(i) Vena cava is associated with human circulatory system.
(ii) Glomerulus is associated with human excretory system.
(iii) Alveoli are associated with human respiratory system.
(iv) Villi are associated with human digestive system.


Answer: 48
Systolic pressure is the pressure at which the blood leaves the heart through the aorta, during contraction phase.
Diastolic pressure is the minimum pressure in the arteries during the relaxation phase of the heart.
The normal systolic pressure is 120 mm Hg, while the normal diastolic pressure is 80 mm Hg. These values are written as 120/80.


Answer: 49
(a) Heart beat is the rhythmic contraction and relaxation of the heart, which includes one systole (contraction phase) and one diastole (relaxation phase) of the heart. At rest, human heart usually beats 70 to 72 times per minute.
(b) A person’s heart beats faster after running for a while. This is because his body needs more energy after running.
When the heart beats faster, it pumps the oxygenated blood more rapidly to the body organs, thereby providing more oxygen to our cells (for rapid respiration) to produce more energy.


Answer: 50
(a) Blood is a red colour connective tissue that circulates in our body. Blood has an extra-cellular matrix called plasma, where red blood cells, white blood cells and platelets float. Blood is red because of the presence of haemoglobin. Haemoglobin is a red colour pigment, found in red blood cells.
(b) Following are the functions of blood:
It transports oxygen from the lungs to the cells.
It carries carbon dioxide, a waste product, from the body cells to the lungs.
It fights diseases and infections.
It regulates the body temperature.
It carries hormones to different organs of the body.

(c) Other than blood, lymph is a circulatory fluid in human body.


Answer: 51
(a) The organ system that is responsible for the transport of materials inside the human body is known as human circulatory system. In human beings, the organs of circulatory system are heart, arteries, veins and capillaries.
(b) Diagram of human heart:

(c) Single circulation: A circulatory system in which the blood passes through the heart only once in one complete cycle is known as single circulation. It is commonly seen in fishes.
Double circulation: A circulatory system in which the blood travels twice through the heart in one complete cycle is known as double circulation. It is commonly seen in amphibians, reptiles, birds and mammals.


Answer: 52
Working of human blood circulatory system:

The human blood circulatory system is composed of the heart, the blood and the blood vessels. The human heart is divided into four chambers. The upper two chambers are called right and left atrium and the lower two chambers are called the right and the left ventricles. Following are the steps involved in the blood circulation:

  1. The left atrium receives the oxygenated blood from the lungs via the pulmonary vein.
  2. When the left atrium contracts, the oxygenated blood is pumped into the left ventricle.
  3. When the left ventricle contracts, the oxygenated blood is forced into aorta, which transports the blood to all the parts of the body, except the lungs. When oxygenated blood passes through the capillaries of different organs, it gives oxygen to the body cells. Along with oxygen, blood also gives the digested food and other dissolved materials to the body cells. At the same time, carbon dioxide, which is produced as a waste material during respiration, enters into the blood.
  4. From the body tissues, the deoxygenated blood carrying carbon dioxide is pumped back to the heart, into the right atrium, by the vena cava.
  5. When the right atrium contracts, the deoxygenated blood is pumped into the right ventricle. From here, it is taken back to the lungs by the pulmonary artery for oxygenation.
  6. The oxygenated blood is again sent to the left atrium of the heart by the pulmonary vein for being circulated in the body.
  7. The whole process is repeated again and again so as the blood keeps circulating in our body and keeps circulating oxygen, digested food and other materials to all the parts of the body. This blood also keeps on removing waste products (in the form of deoxygenated blood) formed in the cells of the body.

Answer: 53
(a) Haemoglobin is the red colour pigment that carries oxygen in the blood.
(b) Mammals and birds are warm blooded animals. Their energy requirement is high since they constantly require energy to maintain their body temperature. Hence, it is necessary to separate the oxygenated and the deoxygenated blood in mammals and birds as this separation allows a highly efficient supply of oxygen to the blood cells. This is important for producing a lot of energy and for maintaining the body temperature.
(c) (i) An amphibian, such as a frog, has a three-chambered heart, with two auricles and one ventricle.
(ii) A mammal has four-chambered heart. The upper two chambers are called atria and the lower two chambers are called ventricles.
(iii) A fish has only two chambers in its heart, i.e. one auricle and one ventricle.
(d) A fish has a two-chambered heart with one auricle and one ventricle. Since both the auricle and ventricle remain undivided, only deoxygenated blood passes through it. The deoxygenated blood passes from the ventricles into the gills for oxygenation. The oxygenated blood from the gills is then passed to the body parts of the fish where oxygen is utilised and carbon dioxide enters it, thereby making the blood deoxygenated. The deoxygenated blood then returns to the heart to be pumped again into the gills for oxygenation.
Since the blood passes through the heart of the fish only once in one complete cycle of the body, the flow of blood in a fish is known as single circulation.


Answer: 54
(a) Lymphatic system is a network of organs, lymph nodes, lymph ducts and lymph vessels in the human body that make and move the lymph from tissues to the bloodstream.
Following are the functions of lymphatic system:
It collects and transports tissue fluid from the intercellular spaces in all the tissues, back to the veins in the blood stream.
Lymph nodes play an important role in the defence mechanism of the body by killing the germs with the help of lymphocytes present in the lymph nodes and by making antibodies.
They transport larger compounds like enzymes and hormones from their manufactured sites to the blood stream.
(b) Blood pressure is the pressure at which the blood is pumped around the body by the heart. It is always expressed in the form of two factors that are called systolic pressure and diastolic pressure.
Systolic pressure is the pressure at which the blood leaves the heart through the aorta during the contraction phase.
Diastolic pressure is the minimum pressure in the arteries during the relaxation phase of the heart.
(c) The main nitrogenous waste in the human blood is urea. The kidneys remove the urea from the blood and excrete them in the form of a dilute solution called urine.
Kidneys are the main excretory organ of the human body. There are millions of nephrons in each kidney. Each nephron contains a renal corpuscle and a renal tubule. The renal corpuscle consists of capillaries called the glomerulus, enclosed by a capsule called Bowman’s capsule. The blood is filtered in the glomerulus and the filtrate travels through the renal tubules. Here, the materials needed by the body are reabsorbed, while the wastes (like urea) are collected and excreted in the urine.


Answer: 55
(a) The human excretory system consists of two kidneys, two ureters, a bladder and a urethra.


(b) Diagram of the human excretory system:
(c) The main function of excretory system is to remove waste and harmful by-products of the normal metabolic processes from the body.


Answer: 56
(a) Kidneys are the main excretory organ of the human body. There are about millions of nephron in each kidney. Each nephron contains a renal corpuscle and a renal tubule. The renal corpuscle consists of capillaries called the glomerulus, enclosed by a capsule called Bowman’s capsule. The blood containing wastes (like urea) enters the glomerulus. The glomerulus filters the blood. During filtration, the filtrate (containing substances like glucose, amino acids, salts, water and urea) present in the blood travels through the renal tubule where materials needed by the body are reabsorbed, while the wastes like urea are collected and excreted in the urine. The nephron carries the urine into the collecting tubule of the kidney from where it is carried to the ureter. From the ureter, the urine passes into the urinary bladder. The urinary bladder stores the urine until it is forced out of the body, through an opening known as the urethra.

(b) Urine is carried into the urinary bladder through two narrow tubes that are called ureters.
(c) Urethra is the small opening that carries urine out of the body.


Answer: 57
(a) Dialysis is the process of removing waste substances like urea from the blood, using a kidney machine. The patients who are most likely suffering from a severe ailment of excretory system are put on dialysis.

(b) Principal of dialysis:

The procedure of dialysis is based on diffusion of solutes and ultrafiltration of fluid across a semi-permeable membrane. In dialysis, the blood from a convenient artery is pumped into the dialyser of a dialysing machine. A dialyser contains a coiled cellophane tube surrounded by the dialysing solution. The dialysing solution contains water, glucose and salts, which are similar in concentration to those in normal blood. The porous cellophane membrane of the tube allows the passage of molecules based on concentration gradient. As the patient’s blood is passed through the dialysing solution, most of the wastes (like urea) present in it pass through the selectively permeable cellulose tubes into the dialysing solution, thereby cleaning the blood. The clean blood is pumped back to the body through a vein.


Answer: 58
(a) Transport of materials is necessary in plants and animals as every cell needs a regular supply of nutrients and oxygen to provide energy during respiration.
(b) Organisms like plants and animals need special tissues and organs for the transport of substances because tissues and organs can easily transport the essential substances like food, oxygen and water from one part of the body to another. For example, the xylem tissues of roots, stems and leaves are interconnected and form a continuous network of channels to transport water to all parts of the plant body.
(c) Water and minerals are absorbed by the cells of the root hair. The root hair is in direct contact with the water present between the soil particles. As the water is absorbed by the roots from the soil, it is transported to various parts of the plants through the xylem tubes. Water is mainly pulled from the leaves by transpiration. 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 parts of the plant, through interconnected water conduction elements.

(d) The transport of food from the leaves to the other parts of the plant occurs through the vascular tissue called phloem. The food (sugar) made in leaves is loaded into the sieve tubes of phloem tissue by using the energy derived from ATP. As a result, the osmotic pressure in the tissue increases, causing the water to move into it. This high pressure produced in the phloem, moves the food to all the parts of the plant that have less pressure in their tissues. This process is helpful in moving the food materials according to the needs of the plant.


Exercise : Solution of Questions on page Number :75


Answer: 59
(a) red blood cell
Red blood cells do not have nuclei.


Answer: 60
(b) white blood cells
White blood cells make chemicals known as antibodies that help to fight against infection and protect the body from foreign particles.


Answer: 61
(b) fish
The aquatic animals like fish have gills as their respiratory organs. Gills extract oxygen dissolved in water and take away carbon dioxide from the body.
On the other hand, cow, frog and fox, breathe through lungs.


Answer: 62
(c) phloem
In a plant, phloem carries substances (food) upwards as well as downwards.


Answer: 63
(c) sieve plates
Sieve plates do not constitute blood. They are a part of phloem.


Answer: 64
(c) excretory system
Dialysis is the process of removing wastes using an artificial kidney. Hence, if a patient is out on dialysis, he is most likely suffering from a severe ailment of excretory system. It is because kidneys are a part of human excretory system and in case of kidney failure, to remove the accumulated wastes from the body, blood is filtered periodically through an artificial kidney.


Answer: 65
(c) under the fan
Water absorption through roots can be increased by keeping the potted plants under the fan.


Answer: 66
(b) vein
Veins carry carbon dioxide rich blood from the various tissues of the body to the heart.


Answer: 67
(b) ventricles
Ventricles pump oxygenated blood from the heart to the entire body.


Answer: 68
(a) carbon dioxide
The blood leaving the tissues becomes richer in carbon dioxide, i.e. it becomes deoxygenated.


Answer: 69
(b) valves
During contraction, valves prevent the back-flow of blood inside the heart.


Answer: 70
(c) kidney → ureter → bladder → urethra
During blood circulation, blood passes through the kidneys. This blood contains both useful and waste materials. The kidneys filter the wastes from the blood and produce urine. From the kidneys, the urine goes into the urinary bladder through two narrow tubes called ureters. The urinary bladder stores the urine until it is forced out of the body, through an opening known as the urethra.


Answer: 71
(d) Pisces only
In Pisces, the heart does not pump oxygenated blood to different parts of the body. This is because Pisces have two-chambered heart with one auricle and one ventricle. Since both the auricle and ventricle remain undivided, only deoxygenated blood passes through it. The deoxygenated blood then enters the gills for oxygenation from the ventricle.


Answer: 72
(b) pulmonary vein
Pulmonary vein carries oxygenated blood (clean blood) from the lungs into the heart.


Answer: 73
(d) pulmonary vein
Pulmonary vein carries the oxygen rich blood from the lungs to the heart.


Answer: 74
(c) the low air pressure requires more red corpuscles to supply the body cells with oxygen.
At high altitude, the atmospheric pressure of oxygen is low. As a result, the number of red blood cells in the body cannot meet the cell’s demands for oxygen. Therefore, the body increases its red blood cell count in order to supply more oxygen to the body cells, even with less oxygen in the atmosphere. Hence, people living on very high mountains have more red corpuscles in their blood than those living in plains.


Answer: 75
(c) sugar
In plants, the phloem tissue is responsible for the transport of food (in the form of sugar) from the leaves to different parts of the body.


Answer: 76
b) lizard
Lizard is a reptile and it has a three-chambered heart. Birds (e.g. Pigeon) and mammals (e.g. lion) have a four-chambered heart, while Pisces (e.g. fish) have a two-chambered heart.


Answer: 77
(c) urine
The largest amount of nitrogen is excreted from a mammalian body as urine.


Answer: 78
(b) sieve tube
Sieve tube, which forms the phloem, are living cells containing cytoplasm but no nucleus.


Answer: 79
(c) translocation
The process of carrying food from the leaves to other parts of a plant is called translocation.


Answer: 80
(d) tracheids
Tracheids are the only conducting tissue in non-flowering plants.


Answer: 81
(d) transpiration
Transpiration is the loss of water through the stomata of leaves and other aerial parts of the plants in the form of water vapour. It provides a transpirational pull, which is responsible for the upward movement of water and dissolved minerals from the roots to the leaves through the stem.


Answer: 82
(c) capillaries
Capillaries do not have valves, while heart, arteries and veins have valves to prevent the back-flow of blood.


Answer: 83
(a) transport of food
The translocation (transport of food) in phloem takes place by utilising the energy stored in the ATP molecules. It takes place in the sieve tubes with the help of adjacent companion cells, both in upward and downward direction.


Answer: 84
(b) platelets
Platelets release chemicals responsible for blood clotting at the site of a cut or a wound. These chemicals help in the coagulation of blood. The main function of the platelets is to form clot and prevent bleeding.


Answer: 85
(d) pulmonary vein
Veins transport deoxygenated blood from various organs of the body towards the heart. Only pulmonary vein carries the oxygenated blood from the lungs to the heart.


Answer: 86
(b) sphygmomanometer
The device used for measuring blood pressure is called sphygmomanometer.


Answer: 87
(a) nephron
The main excretory unit in the human excretory system is called nephron. It produces urine and maintains the homeostasis of the body.


Answer: 88
(c) urea
Urea is not reabsorbed into the blood capillaries that surround the tubule of a nephron. However, glucose, amino acid and water are reabsorbed.


Answer: 89
(c) dialysis
The process of removing wastes (urea) from the blood using a kidney machine is known as dialysis.


Answer: 90
(a) nephridia
In earthworm, the main excretory organs are nephridia. It functions like a kidney.


Answer: 91
(d) WBCs
White blood cells or WBCs destroy the disease causing germs. They are like soldiers that protect the body from various infections.


Answer: 92
(c) pulse
Pulse is the expansion of the artery each time the blood is forced into it.


Answer: 93
(d) xylem
Xylem transports water and minerals from the soil via the roots to the rest of the plant body.


Answer: 94
(b) snake
Snake is a reptile and has a double circulation in a three-chambered heart. Pisces (e.g. fish) has a single circulation in a two-chambered heart, while mammals (e.g. deer) and birds (e.g. sparrow) have a double circulation in a four-chambered heart.


Answer: 95
(a)
(i) The tissue X is phloem. Phloem is made of living cells and helps in the transport of food from leaves to other parts of the body.
(ii) A sieve tube, which forms the phloem, has tiny pores in its end walls and contains only cytoplasm. It does not have any nucleus. Hence, component A is a sieve tube.
(iii) Companion cell is a component of phloem and has cytoplasm as well as nucleus. Hence, component B is a companion cell.
(b)
(i) Tissue Y is xylem. It is made of dead cells and helps in the transport of water and minerals from the soil via roots to the rest of the plant body.
(ii) Xylem vessel is a component of xylem and has open ends. Hence, component C is xylem.
(iii) Tracheid does not have open ends. Hence, component D is a tracheid.


Answer: 96
(a)
(i) The process by which water and dissolved minerals get into the root hair of a plant is known as diffusion. Hence, A is diffusion.
(ii) The water and dissolved minerals are absorbed by the cells of the root hair, which enter the conducting tissue known as xylem. Hence, B is xylem.
(iii) Transpiration helps in transporting water and dissolved minerals to move up through the xylem tissue (B) in the roots and the stem, and reach the leaves of a plant. Hence, C is transpiration.
(iv) In leaves, the food is prepared by a process known as photosynthesis. Hence, the process D is photosynthesis.
(v) The food synthesised by the leaves of a plant is transported to all the parts of a plant through tissue phloem (E). Hence, E is phloem.
(vi) The process of distributing (or transporting) food made in the leaves to all the parts of the plant is called translocation. Hence, F is translocation.
(b) B represents xylem, while E represents phloem. Out of these, phloem (E) is made of living cells.
(c) E (phloem) contains sieve tubes.
(d) B (xylem) contains tracheids.


Exercise : Solution of Questions on page Number :77


Answer: 97
(a)
(i) Blood is the liquid connective tissue that circulates in our body continuously without stopping. Hence, A is blood.
(ii) & (iii) Our blood contains a pigment called haemoglobin, which imparts it a red colour. Hence, pigment B is haemoglobin and colour C is red.
(b)
(i) White blood cells, fight infection and protect us from diseases. Hence, D refers to white blood cells.
(ii) Platelets are the component of blood, which help in the clotting of blood (A). Hence, E refers to platelets.
(iii) Plasma is a liquid, which consists mainly of water with many substances dissolved in it. Hence, F refers to plasma.
(iv) Red blood cells carry oxygen from the lungs to all the parts of the body. Hence, G refers to red blood cells.
(c) Blood also carries the digested food from the small intestine to all other parts of the body.
(d) E (platelets) and G (Red blood cells) are the cells without nucleus.
(e) Amoeba and grasshopper do not have blood (A) like liquid in their body.


Answer: 98
(a) Heart is the organ in the human body that acts as a double pump. Hence, organ A represents the heart.
(b)
(i) The oxygenated blood from the lungs enters the left atrium (chamber C) via the blood vessel called pulmonary vein (B). Hence, B is pulmonary vein.
(ii) The contraction of left ventricle (chamber D) forces the blood into the blood vessel called aorta (E), which supplies the oxygenated blood to the organs of the body, except the lungs. Hence, E is aorta.
(iii) From the body tissues, the deoxygenated blood is transported back to the heart into the right upper chamber called right atrium (G), by the vena cava (F). Hence, F is vena cava.
(iv) Contraction of chamber G (right atrium) forces the deoxygenated blood into the lower right chamber called right ventricle (H). Finally, the contraction of H (right ventricle), sends the deoxygenated blood into the lungs through the blood vessel called pulmonary artery (I). Hence, I represent pulmonary artery.
(c)
(i) The chamber C represents left atrium.
(ii) The chamber D represents left ventricle.
(d)
(i) The chamber G represents right atrium.
(ii) The chamber H represents right ventricle.


Answer: 99
(a) Lymph (X) is a light yellow colour (Y) liquid that circulates in the human body. It circulates from the body tissues to the heart. Hence, (i) the liquid X is lymph. (ii) The colour Y is light yellow.
(b) The liquid X (lymph) is cleaned of germs and dead cells by a special type of white blood cells called lymphocytes (Z). Lymphocyte helps in fighting infections and diseases. Thus, Z represents lymphocytes.
(c)The liquid X, i.e. lymph, is somewhat similar to plasma.
(d) The liquid X, i.e. lymph, is not red because it does not contain red blood cells that have red colour pigment called haemoglobin.


Answer: 100
(a)
(i) Kidneys are bean shaped organs in the human body, towards the back of the body, just above the waist. Hence, organs P are kidneys.
(ii) Urea is the waste product that is formed by the decomposition of unused proteins in the liver. Hence, the waste substance Q represents urea.
(b)
(i) Urea (substance Q) is brought into kidney (organ P) through blood by an artery called renal artery. Hence, R represents renal artery.
(ii) The numerous tiny filters called nephrons (S) present in the kidneys (organ P), clean the dirty blood by removing the waste product Q (urea). The clean blood then goes into circulation through T, i.e. renal vein. Hence, vein T represents the renal vein.
(c) The tiny filters S are known as nephrons.
(d) The waste substance Q (urea), other waste salts and excess water form a yellowish liquid called urine (U). Urine goes from organ P (kidney) into a bag-like structure V, i.e. urinary bladder, through two tubes W, called ureters. This urine is then thrown out of the body through tube X, called urethra.
Hence, (i) the liquid U is urine, (ii) structure V is urinary bladder, (iii) tubes W is ureters, and (iv) tube X is the urethra.


Answer: 101
(a) Organ A is kidney. Complete damage of the kidney (organ A) can lead to the accumulation of waste material B, i.e. urea, in the blood.
(b) The waste substance B is urea.
(c)
(i) In dialysis, the blood from a convenient artery is pumped into the dialyser of a dialysing machine. The dialyser contains a coiled cellophane tube made of substance E, called cellulose. It is surrounded by the dialysing solution (F). Hence, E represents cellulose.
(ii) F represents the dialysing solution.
(d) The dialysing solution contains water (G), glucose (H) and salts (I), which is similar in concentration to those in normal blood.
(e) The process of removing waste substances like urea from the blood using a kidney machine is known as dialysis.


 

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