LAKHMIR SINGH AND MANJIT KAUR Solutions for Class 10 Biology Chapter 1 - Life Processes

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Chapter 1 - Life Processes Exercise 23

Solution 1
Food is the basic requirement of living organisms for obtaining energy.
Solution 2
Chemical Energy.
Solution 3
Green Plant.
Solution 4
Carbon dioxide and Water.
Solution 5
Saprotrophic.
Solution 6
Saprophytic - Fungi.
Parasitic - Plasmodium.
Holozoic - Human Beings.

Solution 7
Photosynthesis.

Chapter 1 - Life Processes Exercise 24

Solution 8
Sunlight and chlorophyll.
Solution 9
Carbon dioxide and water.
Solution 10
(a) Carbon dioxide.
(b) Oxygen.

Solution 11
A is glucose and B is starch.
Solution 12
Alcohol.
Solution 13
We boil the leaf in Alcohol to remove all its green pigment called chlorophyll.
Solution 14
(a) Chlorophyll.

(b) Green.
Solution 15
Chlorophyll
Solution 16
Chloroplast.
Solution 17
Nitrogen, phosphorus, iron and magnesium.
Solution 18
Leaves.
Solution 19
Guard cells.
Solution 20
Amoeba.
Solution 21
(i) Herbivores.
(ii) Carnivores.
(iii) Omnivores.

Solution 22
(i) Carnivores.
(ii) Herbivores.
(iii) Omnivores.

Solution 23
Chlorophyll.
Solution 24
Ingestion, digestion, absorption, assimilation, egestion.
Solution 25
Amoeba engulfs the food particles with the help of finger like projections called pseudopodia.
Solution 26
Digestive enzymes.
Solution 27
Amoeba has no fixed place for egestion. The undigested food gets collected inside amoeba, then its cell membrane suddenly ruptures and the undigested food is thrown out of the body of amoeba.
Solution 28
Paramecium.
Solution 29
Salivary amylase is present in human saliva. It digests starch.
Solution 30
(i) Small Intestine.
(ii) Large Intestine.

Solution 31
Peristaltic movement.
Solution 32
Oesophagus.
Solution 33
Saliva
Solution 34
Villi.
Solution 35
Large intestine.
Solution 36
Anus.
Solution 37
Small intestine.
Solution 38
Digestive enzymes.
Solution 39
(a) Autotrophs.
(b) Heterotrophs.
(c) Autotrophs, heterotrophs.
(d) Carbon dioxide, water.
(e) Starch.

Chapter - Exercise

Solution
Solution
Solution
Solution
Solution
Solution

Chapter 1 - Life Processes Exercise 25

Solution 52
(a) Hydrochloric acid: It makes the medium of gastric juice acidic so that the enzyme pepsin can digest the proteins properly and also kills any bacteria that might have entered the stomach with food.
(b) Enzymes help in the breaking down of complex organic food materials into simpler forms.

Solution 53
(a) Liver secretes bile which gets stored in the gall bladder. Bile performs two functions:
(i) Makes the acidic food coming from the stomach alkaline so that the pancreatic enzymes can act on it.
(ii) Bile salts breaks the fats present in the food into small globules making it easy for the enzymes to act and digest them.
(b) Trypsin: It is a pancreatic enzyme present in the pancreatic juice. Its function is to digest the proteins.

Solution 54
Liver secretes bile which helps in the emulsification of fats. Pancreas secretes pancreatic juice which emulsifies starch, proteins and fats.
Solution 55
(i) - (c)

(ii) - (a)

(iii) - (d)

(iv) - (b)
Solution 56
(a) Photosynthesis.

(b) Heterotrophs.

(c) Autotrophs.

(d) Chloroplast.

(e) Guard cells.

(f) Pepsin.
Solution 57
(i) - (c)

(ii) - (d)

(iii) - (a)

(iv) - (b)
Solution 40
(a) Chlorophyll is a green coloured pigment present in the leaves of plants. It helps in absorbing energy from sunlight during the process of photosynthesis.
(b) (i) Glucose
(ii) Starch.
Solution 42
(a) Autotrophs are those organisms which can make their own food from carbon dioxide and water. Example: Green Plants.
(b) The conditions necessary for autotrophic nutrition are sunlight, chlorophyll, carbon dioxide and water.

Solution 43
(a) Those organisms which cannot make their own food from inorganic substances like carbon dioxide and water, and depend on other organisms for their food are called heterotrophs. Example: All Animals.

Autotrophic Nutrition Heterotrophic Nutrition
It is that mode of nutrition in which an organism makes its own food from the simple inorganic materials like carbon dioxide and water present in the surroundings (with the help of sunlight energy)

Example: Green Plants
It is that mode of nutrition in which an organism cannot make its own food from simple inorganic materials like carbon dioxide and water, and depends on other organisms for its food.

Example: Animals.
Solution 44
(a) A nutrient can be defined as a substance which an organism obtains from its surroundings and uses it as a source of energy or for the biosynthesis of its body constituents (like tissues and organs). The four important nutrients present in our food are: carbohydrates, fats, proteins and mineral salts.
(b) The various types of Heterotrophic nutrition are:
(i) Saprotrophic nutrition.
(ii) Parasitic nutrition.
(iii) Holozoic nutrition.

Solution 45
(a) X is sunlight energy and Y is chemical energy.
(b) The photosynthesis takes place in the following three steps; (i) Absorption of sunlight energy by chlorophyll.
(ii) Conversion of light energy into chemical energy and splitting of water into hydrogen and oxygen by light energy.
(iii) Reduction of carbon dioxide by hydrogen to form carbohydrates like glucose by utilising the chemical energy

Solution 46
(a) Plants obtain food by a process called photosynthesis.
(b) Plants need nitrogen to make proteins and other compounds. They take up nitrogen from the soil in the form of inorganic salts called nitrates (or nitrites), or in the form of organic compounds which are produced by bacteria from the atmospheric nitrogen.

Solution 47
(i) Saprophytic nutrition: It is that nutrition in which an organism obtains its food from dead organic matter of dead plants, dead animals and rotten bread.
Example: Fungi and many bacteria obtain food by saprophytic nutrition.
(ii) Parasitic nutrition: It is that nutrition in which an organism derives its food from the body of another living organism (called its host) without killing it.
Example: Plasmodium and round worms obtain food by parasitic nutrition.
(iii) Holozoic nutrition: It is that nutrition in which an organism takes the complex organic food materials into its body by the process of ingestion; the ingested food is digested and then absorbed into the body cells of the organism.
Example: Human beings obtain food by holozoic nutrition

Solution 48
(a) Saprophyte - Saprophytes are the organisms which obtain their food from dead plants (like rotten leaves), dead and decaying animal bodies, and other decaying organic matter (like rotten bread).
Example: Fungi and some bacteria.
(b) Parasite: A parasite is an organism (plant or animal) which feeds on another living organism called its host.
Example: Plasmodium and round worm.

Solution 49
(a) The carbon dioxide gas enters the leaves of the plants through the stomata present on their surface.

(b) The water required by the plants for photosynthesis is absorbed by the roots of the plants from the soil through the process of osmosis. The absorbed water is then transported upward through the xylem vessels to the leaves where it reaches the photosynthetic cells and utilized in photosynthesis.
Solution 50
The gastric juice contains three substances; hydrochloric acid, the enzyme pepsin and mucus. Functions:

(a) Hydrochloric acid: It makes the medium of gastric juice acidic so that the enzyme pepsin can digest the proteins properly and also kills any bacteria that might have entered the stomach with food.

(b) Pepsin: The enzyme pepsin digests the proteins present in the food and converts them into smaller molecules.

(c) Mucus: The mucus helps to protect the stomach wall from its own secretions of hydrochloric acid.

Chapter 1 - Life Processes Exercise 26

Solution 58
(a) Parasitic mode of nutrition.

(b) (i) Proteins (ii) Starch (iii) Proteins (iv) Fats.

(c) Absorption of digested foods occurs mainly in the small intestine due to the presence of a large number of finger like projections called villi.
Solution 59
(a) Herbivores eat only plants so they need a longer small intestine to allow the cellulose present in the plants to be digested completely.

(b) If mucus is not secreted, hydrochloric acid will cause the erosion of inner lining of stomach leading to the formation of ulcers in the stomach.

(c) The contraction and expansion movements of oesophagus also called peristaltic movements pushes the food down into the elementary canal.
Solution 60
(a) The opening and closing of stomatal pores is controlled by the guard cells, when water flows into the guard cells, they swell, become curved and cause the pore to open whereas when the guard cells lose water, they shrink, become straight and close the stomatal pore.

(b) Plant kept in continuous light will live longer because it will be able to produce oxygen required for its respiration by the process of photosynthesis.
Solution 61
(a) If all the green plants disappear from the earth, then all the organisms (herbivores, carnivores and omnivores) will die due to starvation as green plants are the source of food for all organisms.

(b) When photosynthesis occurs during the day, the carbon dioxide released by plants by respiration is all used up and not released. Similarly, some of the oxygen produced during photosynthesis is used up in respiration. Since the plant is releasing carbon dioxide and taking in oxygen even during the day, it means that no photosynthesis is taking place.
Solution 62
(a) This plant will not remain healthy for long because vaseline coating closes the stomatal pores on the leaves due to which (i) plant will not get oxygen for respiration (ii) plant will not get carbon dioxide for photosynthesis, and (iii) plant will not get water (and minerals) due to stoppage of transpiration.

(b) (i) Decreases in morning but increases in the afternoon

(ii) Decreases.

(iii) Decreases.
Solution 64
(a) The raw materials for photosynthesis are carbon dioxide and water. The green plants take carbon dioxide from air for photosynthesis. The carbon dioxide gas enters the leaves of the plants through the stomata present on their surface. The water required by the plants for photosynthesis is absorbed by the roots of the plants from the soil through the process of osmosis. The water absorbed by the roots is transported upwards through the xylem vessels to the leaves where it reaches the photosynthetic cells and utilized in photosynthesis.

(b) The conditions for photosynthesis are sunlight, chlorophyll, carbon dioxide and water.

(c) Factors affecting the rate of photosynthesis are (i) Light (ii) Carbon dioxide (iii) Water (iv) Temperature (v) Mineral elements.
Solution 63

(a)

The process by which green plants make their own food (like glucose) from carbon dioxide and water by using sunlight energy in the presence of chlorophyll is called photosynthesis.

(c) The process of photosynthesis takes place in the green leaves of a plant. The carbon dioxide gas required   for making food is taken by the plant leaves from the air which enters the leaves through tiny pores called stomata. Water required for making food is taken from the soil which is transported to the leaves from the soil through the roots and the stem. The sunlight provides energy required to carry out the chemical reactions involved in the preparation of food. The green pigment called chlorophyll absorbs sunlight energy. The photosynthesis takes place in three steps:
(i) Absorption of sunlight energy by chlorophyll.
(ii) Conversion of light energy into chemical energy and splitting of water into hydrogen and oxygen by light energy.
(iii) Reduction of carbon dioxide by hydrogen to form carbohydrates like glucose by utilising the chemical energy.

Solution 68

(a) Digestion of food in human beings: Digestion of food begins in the mouth. The mouth cavity contains teeth, tongue and salivary glands. The teeth cut the food into small pieces, chew and grind it. This is called physical digestion. Salivary glands produce saliva which mixes with the food. This involves chemical digestion of food. The saliva contains an enzyme called salivary amylase which digests the starch and converts it into maltose sugar. Mouth opens into a small funnel shaped area called pharynx which leads to a long tube called oesophagus. It carries the food down into the stomach. The wall of oesophagus is muscular. When the slightly digested food enters the food pipe, the walls of the oesophagus starts contraction and expansion movements called peristaltic movements which push the food into the stomach. Digestion does not take place in the oesophagus.
The glands present on the walls of the stomach secrete gastric juice that contains hydrochloric acid, the enzyme pepsin and mucus. A small amount of gastric lipase is also present that breaks down the fats present in the food. Gastric juice is acidic due to the presence of HCl which is necessary for the pepsin to become active and converts the proteins into peptones. The mucus protects the stomach walls from HCl. From the stomach, the partially digested food goes into the small intestine through sphincter muscle. Small intestine is divided into two parts: Duodenum and Ileum.
Duodenum receives the secretions of two glands, liver and pancreas through a common duct. Liver secretes bile which is alkaline and contains salts to emulsify the fats (or lipids). The bile secreted by the liver is stored in the gall bladder. Pancreas secretes pancreatic juice which contains trypsin, lipase and pancreatic amylase. Trypsin digests the proteins, lipase emulsifies the fats and pancreatic amylase breaks down the starch. Thus, small intestine is the site of complete digestion of carbohydrates, proteins and fats. The walls of ileum secrete succus entericus which completes the digestion process.

(b) The walls of small intestine has finger like projections like villi which increases the surface area for absorption.
(c) Peristaltic movements.

Solution 69
(a) The tooth has hard outer covering called enamel. The part of tooth below enamel is called dentine inside which is the pulp cavity. The pulp cavity contains nerves and blood vessels.



(b) The formation of small cavities (or holes) in the teeth due to the action of acid forming bacteria and improper dental care is called dental caries. This happens as follows: When we eat sugary food, the bacteria in our mouth act on sugar to produce acids. These acids dissolve the calcium salts from the tooth enamel and then from dentine forming small cavities in the tooth over a period of time in our mouth act on sugar to produce acids. These acids dissolve the calcium salts from the tooth enamel and then from dentine forming small cavities in the tooth over a period of time.

(c) If the teeth are not cleaned regularly, they become covered with the sticky, yellowish layer of food particles and bacteria cells called dental plaque. It causes tooth decay. It can be prevented by brushing the teeth regularly as it neutralises the acids.
Solution 70
(a) The various organs of the human digestive system are mouth, oesophagus, stomach, small intestine and large intestine. The glands associated with the human digestive system are salivary glands, liver and pancreas.

(b) (i) Carbohydrates - The digestion of carbohydrates begins in the mouth. The human saliva contains an enzyme called salivary amylase which digests the starch present in the food into maltose sugar. The slightly digested carbohydrates when reaches the small intestine, pancreatic amylase present in the pancreatic juice breaks down the starch. The intestinal juice of the small intestine completes the digestion of carbohydrates and finally coverts it into glucose.

(ii) Fats - The process of digestion of fats begins in the stomach. The glands of stomach secrete a small amount of gastric lipase that breaks down the fats present in the food. From the stomach the partially digested food goes into small intestine where the pancreatic lipase breaks down the emulsified fats. The walls of small intestine secrete intestinal juice which converts the fats into fatty acids and glycerol.

(iii) Proteins - The digestion of proteins begins in the stomach. The glands of the stomach secrete gastric juice which contains an enzyme called pepsin. Pepsin converts the proteins into peptones. Pancreatic juice contains trypsin which digests the proteins into peptides and the intestinal juice completes the process of digestion of proteins thus converting it into amino acids.
Solution 66
(a) (i) Herbivores - Those animals which eat only plants are called herbivores.

Example: Goat and cow.

(ii) Carnivores - Those animals which eat only other animals as food are called carnivores.

Example: Tiger and Lion.

(iii) Omnivores - Those animals which eat both plants and animals are called omnivores.

Example: Human Being and dog.

(b)

Lion Carnivore
Man Omnivore
Dog Omnivore
Goat Herbivore
Crow Omnivore
Elephant Herbivore
Snake Carnivore
Hawk Carnivore
Rabbit Herbivore
Deer Herbivore


(c) The five steps involved in the process of nutrition in animals are (i) Ingestion (ii) Digestion (iii) Absorption (iv) Assimilation (v) Egestion.
Solution 65
(a) Nutrition is defined as a process of intake of nutrients (like carbohydrates, fats, proteins, minerals, vitamins and water) by an organism as well as the utilisation of these nutrients by the organism. Nutrition is necessary for an organism as it provides energy to them from the food they eat.

(b) There are mainly two modes of nutrition:

(i) Autotrophic - Autotrophic nutrition is that mode of nutrition in which an organism makes its own food from the simple inorganic materials like carbon dioxide and water present in the surroundings (with the help of sunlight energy).

Example: Green plants obtain food by autotrophic nutrition.

(ii) Heterotrophic - Heterotrophic nutrition is that mode of nutrition in which an organism cannot make its own food from simple inorganic materials like carbon dioxide and water, and depends on other organisms for its food.

Example: All animals obtain food by heterotrophic nutrition.

(c) The mode of nutrition in (i) round worm and (ii) plasmodium is parasitic nutrition.

Chapter 1 - Life Processes Exercise 46

Solution 1
No.
Solution 2
Ethanol.
Solution 3
Yeast can live without oxygen.
Solution 4
Aerobic respiration.
Solution 5
Lactic acid.
Solution 6
Root hairs.

Chapter 1 - Life Processes Exercise 47

Solution 7
Diffusion.
Solution 8
Stomata.
Solution 9
Lenticels.
Solution 10
Root hair.
Solution 11
(a) Respiration.
(b) Photosynthesis.

Solution 12
Gills.
Solution 13
Earthworm.
Solution 14
Amoeba.
Solution 15
Prawns and mussels.
Solution 16
Bronchi.
Solution 17
Alveoli.
Solution 18
Haemoglobin.
Solution 19
Oxygen and carbon dioxide.
Solution 20
Alveoli.
Solution 21
Alveoli.
Solution 22
Trachea.
Solution 23
Lungs.
Solution 24
(a) Oxygen.

(b) Carbon dioxide.
Solution 25
(a) False.

(b) True.

(c) False.
Solution 26
(a) Lungs.

(b) Alveoli.

(c) Alveoli.

(d) Anaerobic, aerobic.

(e) Fish.
Solution 27
A land plant may die if its roots remain water logged for a long time because too much water expels all the air from in-between the soil particles. Due to this, oxygen is not available to the roots for aerobic respiration. Under these conditions the roots will respire anaerobically producing alcohol which may kill the plant.
Solution 28
(a)

Aerobic respiration Anaerobic respiration

(i) Aerobic respiration takes place in the presence of oxygen.

 


(ii) Complete breakdown of food occurs in aerobic respiration.

(iii) The end products in aerobic respiratin are carbon dioxide and water.

(iv) Aerobic respiration produces a considerable amount of energy.

 

 

 

 

(i) Anaerobic respiration takes place in the absence of oxygen.

 

 

(ii) Partial break down of food occurs in anaerobic respiration.

(iii) The end products in anaerobic respiration are ethanol and carbon dioxide (in yeast) and lactic and (in animal muscles).

(iv) Much less energy is produced in anaerobic respiration.

 

 

 

 



(b) Yeast and some bacteria.
Solution 29
(a) Ethanol and carbon dioxide.
(b) Lactic acid.

Solution 30
Anaerobic respiration takes place in human muscles during vigorous physical exercise because oxygen gets used up faster in the muscle cells than can be supplied by the blood.
Solution 31
(a) Anaerobic respiration in yeast.
(b) Aerobic respiration in humans.
(c) Anaerobic respiration in muscle tissue of animals.

Solution 32
The mechanism by which an organism obtains oxygen from the air and releases carbon dioxide is called breathing.

Difference between breathing and respiration:-

Breathing Respiration
(i) Breathing is a simple process.

(ii) Breathing involves taking in oxygen from the air and releasing carbon dioxide into the air.

(iii) Breathing is a physical process.
(i) Respiration is a complex process.

(ii) Respiration includes breathing as well as the oxidation of food in the cells of the organism to release energy.

(iii) Respiration is a bio-chemical process.

Chapter 1 - Life Processes Exercise 48

Solution 34
During the breathing cycle, when air is taken in and let out, the lungs always contain a certain residual volume of air so that there is sufficient time 'for the oxygen absorbed' into the blood and 'for the carbon dioxide to be released' from the blood.
Solution 35
It is dangerous to inhale air containing carbon monoxide as it binds very strongly with haemoglobin in the blood and prevents it from carrying oxygen to the brain and other parts of the body. Due to lack of oxygen, the person cannot breathe properly and may become unconscious or may even die.
Solution 36

(a) Respiration in amoeba: Amoeba depends on simple diffusion of gases for breathing. The diffusion of gases takes place through the thin cell membrane of amoeba. Amoeba lives in water which contains dissolved oxygen. The oxygen from water diffuses into the body of amoeba through its cell membrane. The oxygen spreads quickly into the whole body and is used for respiration inside the amoeba cell. The process of respiration produces carbon dioxide which diffuses out through its cell membrane into the surrounding water.

 

(b) It is aerobic respiration.

Solution 38

Respiration and fish: The fish has special organ of breathing called gills on both the sides of its head. The gills are covered by gill covers. The fish lives in water which contains dissolved oxygen. The fish breathes by taking in water through its mouth and sending it over the gills. When water passes over the gills, the gills extract dissolved oxygen from the water. The extracted oxygen is absorbed by the blood and carried to all the parts of the fish. The carbon dioxide produced by respiration is brought back by the blood into the gills for expelling into the surrounding water.

Solution 39
The deficiency of haemoglobin in the blood of a person reduces the oxygen carrying capacity of blood resulting in breathing problems, tiredness and lack of energy.
Solution 40
(a) Respiration in roots: The roots of a plant take the oxygen required for respiration from the air present in-between the soil particles by the process of diffusion. The roots have extensions of epidermal cells of a root called root hair which are in contact with the air in the soil. Oxygen diffuses from root hairs and reaches all the other cells of the root for respiration. Carbon dioxide gas produced in the cells of the root during respiration moves out through the root hairs by the process of diffusion. Thus, the respiration in roots occurs by diffusion of respiratory gases through the root hairs.
(b) Respiration in stems: The stems of herbaceous plants takes place through stomata. The oxygen from the air diffuses into the stem of a herbaceous plant through stomata and reaches all the cells for respiration. The carbon dioxide produced diffuses out through stomata. In woody stems, the bark has lenticels for the exchange of gases.
(c) Respiration in leaves: The leaves of a plant has tiny pores called stomata through which the exchange of respiratory gases takes place by diffusion. Oxygen from air diffuses into a leaf through stomata and reaches all the cells, where it is used for respiration and the carbon dioxide produced diffuses out from the leaf into the air through stomata.

Solution 41
(a) Aquatic animals are the animals which live in water and the terrestrial animals are the animals which live on land.
(b) The aquatic animals use the oxygen dissolved in water to carry out respiration. The terrestrial animals obtain oxygen from air.

Solution 42
Fishes die when taken out of water because they do not have lungs to utilize the oxygen of air for breathing and respiration. They have gills which can extract only dissolved oxygen from water.
Solution 43
The rate of breathing in aquatic animals is much faster than terrestrial animals because the amount of oxygen dissolved in water is low as compared to the amount of oxygen dissolved in air.
Solution 44
 The energy currency of the cell is 'ATP'. It is produced in cytoplasm in lower organisms which respire anaerobically. In higher organisms, 'ATP' is produced in mitochondria when they respire aerobically.
Solution 45
Plants do not move. In a large plant body there are many dead cells like sclerenchyma as a result it requires less energy as compared to animals.
Solution 46
If humans also had gills then the deep sea divers could remain under sea water even without carrying oxygen cylinders for breathing as they would be able to extract the dissolved oxygen from water for breathing purpose just like a fish does.
Solution 47

(a) The function of respiratory system is to breathe in oxygen for respiration (producing energy from food), and to breathe out carbon dioxide produced by respiration.

(b) The major organs of respiratory system in human beings are: (i) Nose (ii) Nasal Passage (iii) Trachea (iv) Bronchi (v) Lungs and (vi) diaphragm.

Solution 48
(a) When air passes through the nasal passage, the dust particles and other impurities present in it are trapped by nasal hair and mucus so that clean air goes into the lungs.
(b) Trachea does not collapse even when there is no air in it because it is supported by rings of soft bones called cartilage.
(c) During the process of 'breathing in' the air sacs or alveoli of the lungs get filled with air containing oxygen. The alveoli are surrounded by capillaries carrying blood so the oxygen of air diffuses from the alveoli walls into the blood from where it is carried to all the parts of the body.
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 to release energy. Carbon dioxide gas is produced as a waste product during respiration in the cells of the body tissues which 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 as there are millions of alveoli in the lungs which provides a large surface area for the exchange of gases.

Solution 49
(a)

Respiration in plants Respiration in Animals
(i) All the parts of the plants perform respiration individually.

(ii) During respiration in plants there is a little transport of respiratory gases from one part of the plant to the other.

(iii) The respiration in plants occurs at a slow rate.
(i) An animal perfomrs respiration as a single unit.

(ii) Respiratory gases are usually transported over long distances inside an animal during respiration.

(iii) The respiration in animals occurs at a much faster rate.


(b) (i) During daytime when photosynthesis occurs, oxygen is produced. The leaves use some of this oxygen for respiration and the rest of oxygen diffuses out into the air. Carbon dioxide produced by respiration is all used up in photosynthesis by leaves during the daytime. Even more carbon dioxide is taken in from air. Thus, the net gas exchange in leaves during daytime is: Oxygen diffuses out; Carbon dioxide diffuses in.

(ii) At night time, when no photosynthesis occurs and hence no oxygen is produced, oxygen from air diffuses in leaves to carry out respiration. Carbon dioxide produced by respiration diffuses out into air. So, the net gas exchange in leaves at night is: Oxygen diffuses in; Carbon dioxide diffuses out.

(c) Exhaled air contains more carbon dioxide because during the respiration process when oxygen breaks down glucose, then a lot of carbon dioxide is produced hence the exhaled air has a higher proportion of the same.
Solution 50
(a) Respiration is a vital function of the body as it provides energy for carrying out all the life processes which are necessary to keep the organism alive.

(b)

Aerobic respiration Anaerobic respiration
(i) Aerobic respiration takes place in the presence of oxygen.

(ii) Complete breakdown of food occurs in aerobic respiration.

(iii) The end products in aerobic respiration are carbon dioxide and water.

(iv) Aerobic respiration produces a considerable amount of energy.

Example: Human Beings.
(i) Anaerobic respiration takes place in the absence of oxygen.

(ii) Partial breakdown of food occurs in anaerobic respiration.

(iii) The end products in anaerobic respiration are ethanol and carbon dioxide (in yeast) and lactic acid (in animal muscles).

(iv) Much less energy is produced in anaerobic respiration.

Example: Yeast.


(c) (i) Anaerobic respiration.

(ii) Aerobic respiration.
Solution 51
(a) Diffusion is insufficient to meet the oxygen requirements of large multicellular organisms like humans because the volume of human body is so big that the oxygen cannot diffuse into all the cells of the human body quickly and oxygen will have to travel large distances to reach each and every cell of the body.

(b) Large organisms contain a respiratory pigment called haemoglobin which carries the oxygen from the lungs to all the body cells very efficiently.

(c) A terrestrial animal has an advantage over an aquatic animal in regard to obtaining oxygen for respiration that it is surrounded by an oxygen rich atmosphere from where it can take any amount of oxygen.

Chapter 1 - Life Processes Exercise 72

Solution 1
(a) Phloem.
(b) Xylem.

Solution 2
(a) Water.
(b) Food.

Solution 3
Heart.
Solution 4
(a) Arteries.
(b) Veins.

Solution 5
Capillaries.
Solution 6
Valves stop the blood from flowing backward through the heart.
Solution 7

(i) The largest artery in the human body is 'Aorta'.

(ii) The largest vein in the human body is 'Vena Cava'.
Solution 8
Carbon dioxide, water vapour and oxygen.
Solution 9
Glomerulus present in kidneys.
Solution 10
Dialysis.
Solution 11
Blood.
Solution 12
Xylem and phloem.
Solution 13
(a) Phloem.
(b) Xylem.

Chapter 1 - Life Processes Exercise 73

Solution 14
Blood and lymph.
Solution 15
Vena Cava.
Solution 16
Phloem.
Solution 17
(a) Phloem.
(b) Xylem.

Solution 18
Translocation.
Solution 19
Transport of food.
Solution 20
Blood circulatory system and lymphatic system.
Solution 21
(a) Oxygen.
(b) Carbon dioxide.

Solution 22
A fish has single circulation of blood and a frog has double circulation of blood.
Solution 23
(a) True.
(b) False.

Solution 24

Stomata in the leaves and lenticels in the stems are two parts through which a plant releases its gaseous waste products into the air.
Solution 25
Glucose passes through the glomerulus alongwith the filtrate and gets collected in the Bowman's capsule.
Solution 26
Carbon dioxide and urea.
Solution 27
The function of glomerulus is to filter the blood passing through it and initiate urine formation.
Solution 28
Hypertension.
Solution 29
(a) Waste.

(b) Nephron.

(c) Kidneys.

(d) Lymph.

(e) White, red.
Solution 31
Phloem tissue is a vascular tissue which transports the food materials made in the leaves to the other parts of the plant.  Phloem is made up of many cells joined end to end to form long tubes. The cells of the phloem are sieve tubes and companion cell. These are living cells.
Solution 32
(a) The evaporation of water from the leaves of the plants is called transpiration.
(b) The transport of food from the leaves to the other parts of the plant is called translocation.
(c) Phloem.

Solution 33

(a) (i)?

(ii)

(b)

Solution 34
i c
ii a
iii d
iv e
v b
Solution 35
The process of removal of toxic waste from the body of an organism is called excretion. The excretory unit of a kidney is called nephron.
Solution 36
(a) The kidneys remove the poisonous substance urea, other waste salts and excess water from the blood in the form of yellowish liquid called urine.
(b) Urea.
(c) Ureters.
(d) Urinary bladder is a bag which stores the urine temporarily till it is excreted out.

Solution 37
When there is a kidney failure then dialysis machine is used. Dialysis cleans the blood of a person by separating the waste substance (urea) from the blood.
Solution 38
The liquid part of the blood is called plasma.
Platelets help in the coagulation of blood in a cut or wound.

Chapter 1 - Life Processes Exercise 74

Solution 39
(a) There are three types of blood vessels - arteries, veins and capillaries.

(b) Heart needs valves to prevent the backflow of blood so that the blood flows only in one direction.
Solution 40
(i) Cellulose.

(ii) Water, glucose, salts in similar concentration to those in normal blood.

(iii) Urea.
Solution 41
Artery Vein Capillary
(i) It is a thick walled blood vessel. It is a thin walled blood vessel. It is an extremely narrow blood vessel having very thin walls.
(ii) It carries blood from the heart to different parts of the body. It brings blood from the different parts of the body to the heart. They form an extensive network throughout all living cells in the body and connect arteries and veins.
(iii) It can dilate or constrict depending on the regulatory requirement of the body. It cannot dilate or constrict. It can dilate or constrict according to the requirement of the tissue.
(iv) It does not contsin any valve. It contains simple valves which permit blood flow only towards the heart. It does not contain any valves.
Solution 42
(a) Atria
(b) Ventricles
(c) Capillaries
(d) (i) Right side  (ii) Left side

Solution 43

(a) Thevarious methods used by the plants to get rid of their waste products are (i) the plants get rid of gaseous waste products through stomata in leaves and lenticels in stems.
(ii) They get rid of solid and liquid waste by shedding off leaves, peeling of bark and falling of fruits.
(iii) Secreting gums and resins.
(iv) Plants excrete some waste substances into the soil around them.

(b) Excretion in amoeba: In amoeba, the waste material carbon dioxide is removed by diffusion through the cell membrane, but nitrogenous waste and excess water are removed by contractile vacuole.

Solution 44
(a) Lymph is a light yellow liquid. It is a medium of circulation in human body which flows only in one direction - from body tissues to the heart. The functions of lymph are:

(i) It takes part in the nutritive process of the body.

(ii) It protects the body by killing the germs drained out of the body tissues with the help of lymphocytes contained in the lymph nodes, by making antibodies.

(iii) It helps in removing the waste products like fragments of dead cells etc.

(b) If the blood pressure of a person is 120/80 it means that the systolic pressure is 120 mm Hg and diastolic pressure is 80 mm Hg.
Solution 45
High blood pressure is called hypertension. It is caused by the constriction of very small arteries which results in increased resistance to blood flow. Very high blood pressure can lead to rupture of artery and internal bleeding.
Solution 46
The main components of blood are:

(i) Plasma: It carries all the dissolved substances such as proteins, digested food, common salt etc from one part to another part of the body.

(ii) Red blood corpuscles (RBC): It carries oxygen from the lungs to all the cells of the body.

(iii) White blood corpuscles (WBC): It fights infection and protects us from diseases.

(iv) Platelets: It helps in the coagulation of blood in a cut or wound.
Solution 47
(i) Circulatory system.

(ii) Excretory system.

(iii) Respiratory system.

(iv) Digestive system.
Solution 48
The maximum pressure at which the blood leaves the heart through the main artery (Aorta) during contraction phase is called systolic pressure.

The minimum pressure in the arteries during relaxation phase of the heart is called the diastolic pressure.

The normal blood pressure values are:

Systolic pressure: 120 mm Hg.

Diastolic pressure: 80 mm Hg.
Solution 49
(a) Heart beat: One complete contraction and relaxation of the heart is called a heart beat. The usual heart beat rate at rest is 72 times /minute.
(b) The heart beats faster when a person runs for a while because the body needs more energy under these conditions.

Solution 50
(a) Blood is a red coloured liquid which circulates in our body. It is red because it contains a pigment called haemoglobin in its red cells.
(b) Functions of blood:
(i) It carries oxygen from the lungs to different parts of the body.
(ii) It carries carbon dioxide from the body cells to the lungs for breathing out.
(iii) It carries digested food from the small intestine to all the parts of the body.
(iv) It carries waste product called urea from the liver to the kidneys for excretion in the form of urine.
(v) It protects the body from diseases.
(c) Lymph.

Solution 51

(a) Human circulatory system is a system which is responsible for the transport of materials inside the body. The various organs of the circulatory system in humans are: heart, arteries, veins and capillaries.

(b)

(c) Single circulation is a type of circulatory system in which the blood passes through the heart only once in one complete cycle of the body.
Double circulation is a circulatory system in which the blood travels twice through the heart in one complete cycle of the body.

Solution 52
Working of Human blood circulatory system takes place in the steps below:

(i) When the muscles of all the four chambers are relaxed, the pulmonary vein brings the oxygenated blood from the lungs in the left atrium of the heart.

(ii) When the left atrium contracts, the oxygenated blood is pushed into the left ventricle through valve V1.

(iii) When the left ventricle contracts, the oxygenated blood enters the main artery called aorta from which it goes to the different body organs through small branches called arterioles and capillaries.

(iv) The main artery carries the blood to all the organs of the body head, arms etc except the lungs. The oxygenated blood gives off oxygen, digested food and dissolved materials to the body cells. The carbon dioxide produced in the cells enters the blood. The deoxygenated blood enters main vein called vena cava which carried it to the right atrium of the heart.

(v) When the right atrium contracts, the deoxygenated blood enters right ventricle through valve V2.

(vi) When the right ventricle contracts, the deoxygenated blood enters the lungs through pulmonary artery and releases carbon dioxide and absorbs fresh oxygen from air. The blood becomes oxygenated again and is sent to the left atrium of heart by pulmonary vein for circulation in the body. This whole process is repeated continuously.

Solution 53
(a) Haemoglobin.
(b) It is necessary to separate the oxygenated blood from mixing with deoxygenated blood as mammals and birds have high energy needs because they constantly require energy to maintain their body temperature.
(c) (i) Three chambered heart.
(ii) Four chambered heart.
(iii) Two chambered heart.
(d) The fish has a two chambered heart. Oxygenation of the blood takes place in the gills. The oxygenated blood from the gills is supplied to the body parts of the fish where oxygen is utilized and carbon dioxide enters into it making it deoxygenated. The deoxygenated blood returns to the heart to be pumped into gills again.

Solution 54
(a) Lymphatic system: A system of tiny tubes called lymph vessels (lymphatics) and lymph nodes (lymph glands) in the human body which transports the liquid called lymph from the body tissues to the blood circulatory system is called lymphatic system.
Functions of lymphatic system: (i) It takes part in the nutritive process of the body. (ii) It protects the body by killing the germs drained out of the body tissues with the help of lymphocytes contained in the lymph nodes, by making antibodies. (iii) It helps in removing the waste products like fragments of dead cells etc.
(b) Blood pressure: The pressure at which the blood is pumped around the body by the heart is called blood pressure. The two factors which expresses the blood pressure a person are systolic pressure and diastolic pressure.
(c) Urea is the main nitrogenous waste in human blood. It is removed from the body in the form of urine through the kidneys.

Solution 55

(a) The excretory system of human beings consists of the following main organs: two kidneys, two ureters, bladder and urethra.

(c) The excretory system removes the poisonous waste substances from the body in the form of urine and maintains ionic balance called osmoregulation.

Solution 56
(a) Urine formation: The dirty blood containing waste like urea enters the glomerulus which filters the blood. During filtration, the substance like glucose, amino acids, salts, water, urea etc present in the blood pass into Bowman's capsule and then enter the tubule of nephron. When the filtrate containing useful substances as well as the waste substances passes through the tubule, the useful substances like glucose, amino acids, most salts and water are reabsorbed into the blood through blood capillaries surrounding the tubule. Only the waste substances like urea, some unwanted salts and excess water remains behind in the tubule. This yellowish liquid is called urine.



(b) Urinary bladder.

(c) Urethra is a tube which passes out the urine from the body collected in the urinary bladder.
Solution 57
(a) Dialysis: The procedure used for cleaning the blood of a person by separating the urea from it is called dialysis. The patients with kidney failure are put on dialysis.

(b) Principle of Dialysis: The blood from an artery in the patients arm is made to flow into the dialyser of a dialysis machine made of long tubes of selective permeable membrane (like cellulose) which are coiled in a tank containing dialysing solution. The dialysing solution contains water, glucose and salts in similar concentrations to those in normal blood. As the patient's blood passes through the dialysing solution most of the waste like urea present in it pass through the selectively permeable cellulose tubes into the dialysing solution. The clean blood is pumped back into a vein of the patients arm.

Solution 58

(a) Transport in organisms (plants and animals) is necessary as it absorbs all essential substances and transports them to all parts so that they reach each and every cell of the body.
(b) Special tissues and organs are needed for the transport of substances in plants and animals because these tissues and organs can pick up the essential substances like food, oxygen, water, etc at one end of their body and carry them to all other parts.
(c) Water and minerals are transported to various parts of the plant by xylem tissues called xylem vessels and tracheids. Plants take in water from the soil through the roots. The water containing minerals called cell sap is carried by the xylem vessels to all the parts of the body. The roots have root hairs to absorb water and minerals from the soil by diffusion and then pass from cell to cell by osmosis through epidermis, root cortex, endodermis and then reach the root xylem. The water enters the root xylem into the stem xylem and then reaches the leaves from the petioles.

(d) Transportation of food in plants: The transport of food from the leaves to other parts of the plant is called translocation. Phloem tissue transports the food from the leaves to the other parts of the plant. The movement of food in phloem takes place by utilising energy. The sugar made in the leaves is loaded into the sieve tubes of phloem by using ATP. Water enters the sieve tube containing sugar which causes high pressure and pushes the food to all the parts of the plant having low pressure. This is how the food is transported according to the needs of the plant.