KSEEB Class 8 Science Important Questions Chapter 19 Nutrition and Respiration

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Karnataka State Syllabus Class 8 Science Important Questions Chapter 19 Nutrition and Respiration

Question 1.
What are life processes? List the life processes basic to all living beings.
Answer:
The basic functions all living organisms have to carry out in order to support and sustain their life are called life processes. Some of the life processes include nutrition, respiration, reproduction, growth, excretion, response to stimuli and so on.

Question 2.
What is nutrition?
Answer:
The process by which organisms obtain, digest and assimilate their food is called nutrition.

Question 3.
Which are the two major types of nutrition found in organisms?
Answer:
Nutrition modes found in organisms are broadly classified into two types

• autotrophic nutrition
• heterotrophic nutrition.

Question 4.
Show by a diagram various types of nutrition found in plants. Modes of nutrition in plants
Answer:

Question 5.
What is autotrophic nutrition?
Answer:
The method of nutrition in which organisms prepare their own food is called autotrophic nutrition.

Question 6.
What are autotrophs? Give an example.
Answer:
Organisms which prepare their own food are called autotrophs. E.g. Green plants.

Question 7.
What is photosynthesis?
Answer:
The process of manufacture of food by green plants in the presence of sunlight by using carbon dioxide and water is called photosynthesis.

Question 8.
What are the raw materials required for photosynthesis?
Answer:
The raw materials required for photosynthesis are carbon dioxide and water.

Question 9.
What are the products of photosynthesis?
Answer:
The products of photosynthesis are carbohydrates and oxygen.

Question 10.
Define photosynthesis. Write the chemical equation for photosynthesis.
Answer:
The process of manufacture of food by green plants in the presence of sunlight is called photosynthesis.

Glucose produced during photosynthesis is stored in the form of starch.

Question 11.
Which is the pigment in green plants that helps to trap sunlight?
Answer:
A pigment called chlorophyll present in green plants helps to trap sunlight.

Question 12.
Describe an experiment to show the presence of starch in a leaf.

OR

Explain the method of testing a leaf for starch.
Answer:
Take a green leaf from a plant. Place it in boiling water for about two minutes. Now take out the leaf from water and boil it in 90% ethyl alcohol over a water bath till the leaf decolourizes. Gently remove the leaf and wash it in cold water. Spread the leaf on a surface and pul a few drops of iodine solution on it. If starch is present, the leaf turns blue. If starch is not present, then the leaf turns brown.

Question 13.
Describe a simple activity to show that carbon dioxide is essential for photosynthesis.
Answer:

Take two potted plants A and B. Keep them in a dark room for two days. Place a beaker containing potassium hydroxide solution near to A and sodium bicarbonate solution near to B. Cover both the plants with polythene bags as shown in the figure. Make the two plants airtight. Potassium hydroxide absorbs carbon dioxide and sodium bicarbonate releases carbon dioxide.

Thus, carbon dioxide is available for plant B and it is not available for plant A. Place the two plants in sunlight for about 48 hours. Remove the polythene cover. Test a leaf from each plant for the presence of starch. The leaf from plant A does not contain starch while the leaf from plant B contains starch. This activity shows that carbon dioxide is essential for photosynthesis.

Question 14.
Front where do green plants obtain minerals and water?
Answer:
Green plants take in minerals and water from the soil through their roots.

Question 15.
What are stomata?
Answer:
The minute openings on the surface, especially on the lower surface, of leaves are called stomatal openings. They are simply called stomata.

Question 16.
Explain a way to observe stomata in a green plant.
Answer:

Take a leaf from Nerium plant. Cut a thin section of it along the mid rib. Place the section in water taken in a petridish. Place the leaf section on a slide. Add a drop of water and place a cover slip over the specimen. Place the slide under a microscope and observe. The slide shows minute openings. These are nothing but stomata.

Question 17.
What is the role of stomata in photosynthesis?
Answer:
Stomata help in the exchange of gases. Carbon dioxide, which is essential for photosynthesis, is taken in through the stomata. Oxygen, which is produced during photosynthesis, is released to the environment through the stomata. Further, stomata help to throw out excess of water present in the plant. This is done by a process called transpiration.

Question 18.
Draw a neat labelled diagram of the cross section of a leaf.
Answer:

Question 19.
Describe an activity to show that oxygen is produced during photosynthesis.
Answer:
Take some water plant such as hydrilla in a beaker containing pond water. Cover the plants with a funnel. Invert a test tube over the stem of the funnel. Ensure that the test tube is fdled with water completely.

Place the apparatus in the sun for a few hours. A gas gets collected in the test tube. A burning splinter bursts into flame when brought close to the gas. This shows that oxygen is produced during photosynthesis.

Question 20.
Where exactly does photosynthesis occur in green leaves?
Answer:
Photosynthesis takes place in chloroplasts of the cells in the leaves.

Question 21.
Draw a neat diagram of a chloroplast and mark Grana and Stroma in it.
Answer:

Question 22.
Which are the two phases of photosynthesis?
Answer:
Photosynthesis proceeds in two phases. The two phases are

• Light dependent reaction (light reaction)
• Light independent reaction (dark reaction).

Question 23.
What is ‘light dependent reaction’ of photosynthesis? Where does it occur?
Answer:
The phase of photosynthesis that takes place in the presence of sunlight is called light dependent reaction or light reaction. Light dependent reaction of photosynthesis occurs in the grana of the chloroplasts.

Question 24.
What is the reaction that occurs during the light dependent phase of photosynthesis?
Answer:
During the light dependent phase of photosynthesis, water decomposes into hydroxyl ions and hydrogen ions in the presence of sunlight in the grana of chloroplasts. Light energy is converted into chemical energy and stored in the form of ATP.

Question 25.
What is ‘light independent reaction’ of photosynthesis? Where does it occur?
Answer:
The phase of photosynthesis that does not require sunlight is called light independent reaction. This phase is also called dark reaction. The light independent reaction occurs in the stroma of chloroplasts.

Question 26.
What is the reaction that occurs during the light independent phase of photosynthesis?
Answer:
During the light independent phase of photosy nthesis, carbon dioxide is reduced to starch by using the energy released during the light dependent reaction.

Question 27.
Distinguish between light dependent reaction and light independent reaction of photosynthesis.

OR

Differentiate between the two phases of photosynthesis.
Answer:

Light dependent reaction	Light independent reaction
1. This phase of photosynthesis requires the presence of sunlight.	1. This phase of photosynthesis does not require sunlight.
2. It lakes place in the grana of chloroplasts.	2. It takes place in the stroma of chloroplasts.
3. During this phase, water is decomposed into hydrogen ions and hydroxyl ions.	3. During this phase, carbon dioxide is reduced to starch.

Question 28.
What adaptations do yon see in Drosera to obtain nitrogen?
Answer:
Drosera usually grows in nitrogen-deficient soil. It derives the required nitrogen by trapping and digesting insects.

Question 29.
Define the following: Heterotrophic nutrition, heterotrophs.
Answer:
Heterotrophic nutrition: The mode of nutrition in which organisms obtain their food from other living beings is called heterotrophic nutrition. Heterotrophs: Organisms which cannot prepare their own food and hence depend on other organisms for their nutrition are called heterotrophs.

Question 30.
What are insectivorous plants? Give two examples.
Answer:
Certain autotrophic plants that capture and digest insects to obtain nitrogen compounds are called insectivorous plants. eg: Drosera, Nepenthes, etc.

Question 31.
Why do insectivorous plants trap and digest insects although they are autotrophs?
Answer:
Insectivorous plants grow in marshy habitats which lack nitrogen. In order to compensate for the non-availability of nitrogen, insectivorous plants trap and digest insects.

Question 32.
Why can’t other plants generally grow in regions where insectivorous plants are found in plenty?
Answer:
Other plants generally are not known to grow in regions where insectivorous plants are found in plenty because the soil is highly deficient in nitrogen. Other plants are not adapted to find nitrogen by other means. Hence, they do not grow there.

Question 33.
What are epiphytes? Give an example.
Answer:
Green plants growing on other trees to get support and shelter are called as epiphytes. eg: Orchids.

Question 34.
How do orchids take in water?
Answer:
Orchids are epiphytes. They have special type of water-absorbing tissues that occur on the aerial roots. Orchids use these aerial roots to absorb moisture directly from the atmosphere.

Question 35.
Distinguish between autotrophic nutrition and heterotrophic nutrition.
Answer:
Autotrophic nutrition:

1. It occurs in green plants and some bacteria.
2. They need chlorophyll and sunlight.
3. C0₂ and H₂0 combine together to form organic compounds.
4. They take in inorganic components as their food.

Heterotrophic nutrition:

1. It occurs in animals and insectivorous plants.
2. These are not needed.
3. In this type of nutrition, organisms depend on plants and herbivores for their food.
4. They take in organic components as their food.

Question 36.
What are saprophytes? Give two examples.
Answer:
Organisms which derive nutrition from dead and decaying organic matter are known as saprophytes. E.g. Bacteria, Rhizopus, Agaricus, etc.

Question 37.
Why is agaricus considered a saprophyte?
Answer:
Agaricus has no chlorophyll. It derives nutrition from decaying organic matter. This is why it is considered a saprophyte.

Question 38.
What is parasitic mode of nutrition?
Answer:
A mode of heterotrophic nutrition where an organism lives on the body surface or inside the body of another type of organism and derives nutrition directly from the body of the host is called parasitic nutrition.

Question 39.
What are parasites? Give two examples.
Answer:
Organisms that live inside or on the surface of another organism from which they obtain their food are called parasites. eg: Cuscuta, Viscum, etc.

Question 40.
In the parasitic mode of nutrition, explain the terms ‘parasite’ and ‘host’ with an example.
Answer:
Head lice live on the head of humans. They derive nutrition from human beings. Here, lice arc parasites and human being on whose head lice thrive is the host.

Question 41.
What is mutualism?

OR

What is symbiosis?
Answer:
The relationship between two species of organisms in which both benefit from the association is called mutualism. This type of relationship is also known as symbiosis.

Question 42.
Give two examples for symbiosis.
Answer:
A bacteria called Escherichia coli live in our large intestine. The bacteria get shelter and nutrition from humans. In return, E.coli produce vitamin B and make it available to us. This is a relationship in which human intestine provides nutrition to E.coli and the bacteria return this help by producing vitamin B.

This is an example for mutualism. Lichens are a combination of an alga and a fungus. The association between these two is for mutual benefit. The fungus derives nutrition from alga. In return, alga gets water from fungus.

Question 43.
Give an example of mutualism in plants.
Answer:
We find a symbiotic relationship between bacteria called rhizobium and leguminous plants. The bacteria provide nitrogen to the plant at the nodules. The plant provides shelter to rhizobium. This is a mutually beneficial relationship.

Question 44.
Why are animals called heterotrophs?
Answer:
Animals cannot prepare their own food and hence depend on other organisms for their nutrition. Hence, they are called heterotrophs.

Question 45.
Why is nutrition in animals said to be holozoic?
Answer:
Animals derive their nutrition by the ingestion of liquid or solid organic material, digest it and utilize it for their activities. This is why animals are said to have holozoic mode of nutrition.

Question 46.
Show by a diagram the various modes of nutrition found in animals.
Answer:

Question 47.
Which are the steps involved in the holozoic nutrition in animals?
Answer:
The holozoic nutrition in animals involves the following steps:

• Ingestion
• Digestion
• Absorption
• Assimilation, and
• Egestion.

Question 48.
With reference to holozoic nutrition found in animals, give the meaning of the following terms

1. ingestion
2. digestion
3. absorption
4. assimilation
5. egestion.

Answer:

1. Ingestion: The process of taking in of food by animals into their body is called ingestion.
2. Digestion: The process of breaking down of complex molecules present in food into simpler molecules is called digestion.
3. Absorption: The process by which digested nutrients are absorbed and transported to cells and tissues through blood is called absorption.
4. Assimilation: The process of conversion of absorbed food into complex substances such as proteins and vitamins required by the body is called assimilation.
5. Egestion: The throwing out of the undigested food particles from the body of an animal is called egestion.

Question 49.
Why is amoeba called a unicellular organism?
Answer:
The entire body of amoeba is made up of only one cell. This is why amoeba is considered a unicellular organism.

Question 50.
Why is amoeba called an omnivore?
Answer:
Amoeba feeds on a variety of foods which include bacteria, diatoms, unicellular algae, minute protozoa and zooplankton. This is why amoeba is an omnivore.

Question 51.
What type of nutrition do you find in amoeba?
Answer:
We find holozoic mode of nutrition in amoeba.

Question 52.
Why is nutrition in amoeba said to be holozoic?
Answer:
Amoeba consumes solid organic particles as its food. However, these food particles are broken down into simple molecules during the process of digestion. This is why nutrition in amoeba is said to be holozoic.

Question 53.
What are pseudopodia in amoeba? What are its functions?
Answer:
The finger-like projections on the body of amoeba are called pseudopodia. Pseudopodia have three major functions

1. It is the organ of locomotion. They help amoeba to move.
2. They also help to ingest food particles into its body.
3. They also help in egestion of undigested food particles from the body.

Question 54.
Explain the process of ingestion in amoeba.
Answer:

When amoeba senses a food particle, it projects its pseudopodia and surrounds the food particle. The food particle enclosed by pseudopodia eventually forms a cavity called food vacuole.

Question 55.
Which is the organ of digestion of food in amoeba? Name two enzymes that help amoeba to digest food.
Answer:
The food vacuole is the organelle for digestion of food in amoeba. Amylase and proteinase are the two enzymes produced in amoeba which help in the digestion of food.

Question 56.
Amoeba cannot digest fat. Why?
Answer:
Amoeba produces two types of digestive enzymes namely amylase and proteinase. Amylase helps in the digestion of carbohydrates while proteinase assists in the digestion of proteins. Amoeba does not produce any enzyme that digests fats. Therefore, it is incapable of digesting fats.

Question 57.
Explain briefly the nutrition in amoeba.
Answer:
Amoeba is a holozoic unicellular organism. When an amoeba senses a food particle, its pseudopodia will extend and surround the food particle. This forms a food vacuole. The food vacuole produces digestive enzymes which will digest the food particles through chemical action.

The digested food is absorbed into the cytoplasm by the process of diffusion. The absorbed food is utilized for various life processes. The undigested food is thrown out of the body with the help of pseudopodia.

Question 58.
Why is cockroach considered an omnivore?
Answer:
Cockroach feeds on all kinds of food which includes paper, cloth, plastic, vegetables, rubber, chillies and wood. This is why cockroach is considered an omnivore.

Question 59.
Which are the three major parts into which the body of cockroach is divided?
Answer:
The body of cockroach is divided into three major parts. They are head, thorax and abdomen.

Question 60.
Draw a neat diagram showing the digestive system in cockroach.
Answer:

Question 61.
What are the functions of antennae found near the head of cockroach?
Answer:
There is a pair of feelers in the head region of cockroach. These feelers help to sense food and to push food into its mouth.

Question 62.
What is the function of the following enzymes in the digestion of food in cockroach: Amylase, Maltase, Protease, Invertase, Tryptase and Lipase?
Answer:

1. Amylase: The enzyme amylase converts starch into maltose sugar.
2. Maltase: The enzyme maltase converts maltose sugar into glucose.
3. Protease: The enzyme protease helps in the digestion of proteins.
4. Tryptase: The enzyme tryptase helps in the digestion of protein matter.
5. Lipase: The enzyme lipase helps in the digestion of lipids.

Question 63.
What is the enzyme present in the saliva of cockroach? What is its function?
Answer:
The saliva of cockroach contains a digestive enzyme called amylase. Salivary amylase helps to convert starch into maltose sugar.

Question 64.
Which are the three major parts of alimentary canal of cockroach?
Answer:
The entire digestive tract extending from mouth to anus is called alimentary canal. The alimentary canal in cockroach has three major parts. They are foregut, midgut and hindgut.

Question 65.
Describe briefly the process of digestion offood in cockroach.
Answer:
Digestion in cockroach begins in the mouth where it gets crushed into finer particles. The saliva wets the particles and masticates it. The enzyme amylase present in the saliva partially digests the starch. The food is then swallowed.

The food then enters the crop through the oesophagus where it is temporarily stored. The food from the crop then goes to the gizzard where it is ground nicely. The food then goes into the stomach. The digestive enzymes secreted by the gastric caecae act upon the food in the stomach.

These enzymes include amylase, maltase, invertase, tryptase and lipase. The remaining carbohydrates, proteins and fats are digested here. The digested food is absorbed through the stomach walls into the surrounding space w hich is filled with a fluid called haemocoel.

From here, it is transported to the different body parts. In the hindgut. absorption of water takes place and the undigested food is formed into almost dry pellets. These are excreted through the anus as faeces.

Question 66.
What is the excretory organ in cockroach called? Where are they located?
Answer:
Excretory organs in cockroach arc known as Malpighian tubules. They are found at the junction of the midgut and hind gut.

Question 67.
Which part of the alimentary canal in cockroach acts as the grinding chamber of food?
Answer:
The gizzard serves as the grinding chamber where food particles are further ground into a fine paste.

Question 68.
Why are humans called omnivores?
Answer:
Human beings consume both plant and animal products as their food. This is why they are called omnivores.

Question 69.
Name the major parts of human digestive system.
Answer:
The human digestive system includes mouth, oesophagus, stomach, small intestine, large intestine, rectum, anus, liver, gall bladder and pancreas.

Question 70.
In which organ of our body does digestion of food begin? Where does it end?
Answer:
In humans, the digestion of food begins in the mouth and ends in the small intestine.

Question 71.
Which are the two types of digestion that occur in humans?
Answer:
The two types of digestion in humans are

• mechanical digestion
• chemical digestion.

Question 72.
Distinguish between mechanical digestion and chemical digestion in humans.
Answer:

Mechanical digestion	Chemical digestion
1. This refers to the physical breaking down of the food into smaller and finer particles.	This refers to the breaking down of complex organic molecules of food into simpler molecules through chemical action.
2. This takes place in the mouth with the help of teeth and tongue.	This process begins in the mouth and ends in the small intestine.
3. This involves only physical changes that help subsequent chemical reactions.	This involves chemical changes in food.

Question 73.
Name the organs involved in mechanical digestion of food in humans.
Answer:
Teeth and tongue in the mouth are involved in mechanical digestion of food.

Question 74.
Draw a neat labelled diagram of the human digestive system and label the parts.
Answer:

Question 75.
What are salivary glands? How are its secretions helpful to us in digestion?
Answer:
There are three pairs of glands in the buccal cavity which secrete salivary juice. These glands are called salivary glands. The saliva helps in the digestion of food in two ways. It wets the food and helps to make into a soft paste called bolus. This facilitates easy swallowing. Secondly, an enzyme present in saliva assists in partial digestion of carbohydrates.

Question 76.
Name the digestive enzyme present in saliva. What is its function?
Answer:
The saliva in humans contains a digestive enzyme called amylase. Amylase helps in the partial digestion of carbohydrates. It converts starch into maltose sugar.

Question 77.
What is the role of tongue in the digestion of food?
Answer:
Tongue helps the teeth in crushing the food into smaller particles. It mixes saliva with food by turning and rolling it. This helps to make food into a soft paste. This makes swallowing easier.

Question 78.
What is bolus?
Answer:
The food that we take into our mouth is broken into smaller pieces by the teeth. The saliva mixes with the food and forms a soft paste. This is called bolus.

Question 79.
What is the common passage for both food and air in the throat of a human being?
Answer:
The common passage for food and air in the throat is called pharynx.

Question 80.
Name the part which prevents food particles from entering wind pipe in humans.
Answer:
A tissue called epiglottis prevents food particles from entering into the wind pipe. The epiglottis is a flap of cartilage located in the throat behind the tongue and in front of the larynx.

Question 81.
What is larynx? Where is it located? What is its function in digestion?
Answer:
The beginning part of the wind pipe (also called trachea) is called larynx. It is located behind the tongue in front of the oesophagus. Larynx gives a safeguarded pathway for the movement of air between pharynx and wind pipe. During swallowing, the cartilaginous flap closes the entrance of the larynx and thus prevents the entry of food and liquid into the wind pipe.

Question 82.
We are often advised not to talk while swallowing food. Give reason.
Answer:
The wind pipe (trachea) should remain open while we are talking. If we try to swallow food while talking, there is a risk of food entering into the wind pipe which is dangerous. This is why we must not talk while swallowing food or liquids.

Question 83.
What is oesophagus? What is its role in digestion of food?
Answer:
The tubular organ of the alimentary canal which connects the pharynx to the stomach is called oesophagus. Oesophagus has no role in digestion of food. However, it serves as the pathway for the movement of food from the pharynx to the stomach.

Question 84.
What is peristalsis? What is its function?
Answer:
The movement caused by the rhythmic contraction and relaxation of the muscles of the alimentary canal is called peristalsis. Peristalsis in the oesophagus helps to push the bolus into the stomach. It also helps in the movement of substances through the alimentary canal.

Question 85.
A person has lost peristalsis movements. What problems does he face related to digestion of food?
Answer:
A person who has lost power of peristalsis will find it difficult to swallow food, push the bolus into the stomach and may also suffer from constipation.

Question 86.
Name the digestive juice secreted by the stomach in humans. What are the digestive enzymes present in it?
Answer:
The digestive juice secreted by the human stomach is called gastric juice. This juice contains two digestive enzymes called pepsin and rennin.

Question 87.
What is the role of enzymes pepsin and rennin present in gastric juice?
Answer:
The enzyme pepsin present in gastric juice converts proteins into polypeptides. The enzyme rennin converts milk into curds.

Question 88.
What is chyme? What is it made of?
Answer:
The thick semi-liquid mass of partly digested food which is about to move out of the stomach and into the small intestine is called chyme. The chyme consists of partly digested food, water, hydrochloric acid and gastric juice.

Question 89.
Name the acid secreted in the human stomach. What is its function?
Answer:
The human stomach secretes hydrochloric acid. This acid kills the microbes that might have entered the stomach through food and water.

Question 90.
What is the consequence of over-production of acid in the stomach?
Answer:
Over-production of hydrochloric acid in the stomach causes hyperacidity.

Question 91.
Distinguish between bolus and chyme.
Answer:
Bolus:

1. This is formed in the buccal cavity (mouth).
2. This is a semi-solid soft ball consisting of ground food mixed with saliva. It also contains partially digested carbohydrates.
3. Bolus moves from pharynx to the stomach.
4. Only carbohydrate component is partly digested in the bolus.

Chyme:

1. This is formed in the stomach.
2. This is a semi-liquid substance that contains partially digested food, hydrochloric acid, gastric juice and water.
3. Chyme moves from stomach to small intestine.
4. Carbohydrates and proteins are partly digested in the chyme.

Question 92.
Describe briefly the changes food undergoes in the human stomach.
Answer:
Stomach is a muscular sac. The bolus that comes to the stomach through the oesophagus is churned well in the stomach. This helps in mixing the bolus with hydrochloric acid and gastric juice. The gastric juice contains two enzymes called pepsin and rennin.

Pepsin converts proteins into polypeptides and rennin changes soluble milk proteins into insoluble curds. Thus, food is partially digested in the stomach. The food now takes the form of a semi-liquid called chyme. The chyme moves into the small intestine for further digestion.

Question 93.
Name the three digestive juices that act on the chyme in the small intestine of our body.
Answer:
Bile juice, pancreatic juice and intestinal juice act on the chyme in the small intestine.

Question 94.
Where are the following digestive juices produced: gastric juice, bile juice, pancreatic juice and intestinal juice?
Answer:
Gastric juice is produced by the gastric glands in the stomach. Bile juice is produced by the liver. Pancreatic juice is produced by the pancreas and the intestinal juice is produced in the small intestine.

Question 95.
What are the various digestive enzymes present in intestinal juice? State the function of each of these enzymes.
Answer:
Intestinal juice contains digestive enzymes such as maltase, sucrase, lactase, peptidase and lipase. The enzyme maltase converts maltose sugar into glucose. Sucrase converts sucrose into glucose. Lactase converts lactose sugar into glucose. Peptidase converts peptides into amino acids. Lipase helps in the digestion of lipids into simple fats.

Question 96.
What are the various digestive enzymes present in pancreatic juice? State the function of each of these enzymes.
Answer:
The pancreatic juice produced by the pancreas contains enzymes such as amylase, protease and lipase. Amylase converts starch into maltose sugar. Protease breaks polypeptides into smaller peptides. Lipase produced by the pancreas converts complex fats into simple fats.

Question 97.
Name the only digestive juice in the human body which does not contain any digestive enzymes.
Answer:
Bile juice produced by the liver does not contain any digestive enzymes.

Question 98.
What is bile? Where is it produced? Where does it get stored? What is its function in the digestion of food?
Answer:
An alkaline digestive juice in the form of a brownish-yellow or greenish-yellow fluid that is secreted by the liver is called bile. It is stored in the gall bladder. Bile reduces the acidic nature of chyme. It also attracts complex fat molecules and keeps them separate. This facilitates their digestion.

Question 99.
Explain the digestion of food in the small intestine.
Answer:
Partially digested food in the form of chyme comes to the small intestine. The digestive juices secreted by the intestinal walls, liver and pancreas are released into the intestine. The bile assists in the digestion of fats. Pancreatic juice and the intestinal juice contain many digestive enzymes which complete the digestion of carbohydrates, fats and proteins.

Question 100.
What is the final form of carbohydrates, fats and proteins after digestion is complete?
Answer:
Carbohydrates on complete digestion are converted into glucose. Fats are converted into soluble fatty acids and glycerol. Proteins are changed into amino acids.

Question 101.
What happens to the digested food in the small intestine? What are the structures that help this process?
Answer:
The digested food in the small intestine is absorbed into the blood through the wall of the small intestine. This process of absorption of digested food is assisted by structures called villi.

Question 102.
What are villi? What is their function?
Answer:
Finger-like structures on the wall of the small intestine are called villi. Villi absorb the digested food from the small intestine and let them into the blood stream.

Question 103.
What happens to the undigested food in the small intestine?
Answer:
The undigested food moves to the large intestine from the small intestine. The water present in the undigested food is reabsorbed there. The faecal matter gets collected in the rectum which is thrown out through the anus.

Question l04.
In which part of the human digestive system do the following activities take place

1. formation of bolus
2. formation of chyme
3. production of saliva
4. production of hydrochloric acid
5. production of bile
6. absorption of digested food into the blood stream
7. absorption of water from undigested food
8. elimination offaecal matter?

Answer:

1. Bolus is formed in the buccal cavity (mouth).
2. Chyme is formed in the stomach.
3. Saliva is produced in the buccal cavity.
4. Hydrochloric acid is produced in the stomach.
5. Bile is produced in the liver.
6. Absorption of digested food occurs in the small intestine.
7. Absorption of water from undigested food occurs in the large intestine.
8. Elimination of faecal matter occurs through the anus.

Question 105.
What is emulsification?
Answer:
The breaking down of large masses of fat into smaller masses is called emulsification.

Question 106.
Explain briefly the digestion of food in humans.
Answer:
The digestion of food begins in the mouth. The teeth help in cutting and chewing food. The tongue helps the food to mix with saliva. The enzyme amylase present in saliva digests carbohydrates partially. The food is converted into soft balls called bolus which is easily swallowed.

The swallowed food moves into the stomach through oesophagus through peristaltic movement. Digestion continues in the stomach where the bolus gets mixed with hydrochloric acid and gastric juice. The enzymes present in the gastric juice convert proteins into simpler molecules.

Partially digested food from the stomach moves into the small intestine where it gets mixed with bile juice, pancreatic juice and intestinal juice. The enzymes present in these juices convert carbohydrates into glucose, proteins into amino acids and insoluble fats into simpler soluble fats.

Thus, the digestion of food gets completed in the small intestine. The digested food is absorbed into blood by structures called villi on the walls of the small intestine. The undigested food moves into the large intestine where water is reabsorbed. The faecal matter moves into the rectum and is eliminated through the anus.

Question 107.
What is respiration? What is its chief purpose?
Answer:
Respiration is a process of oxidation or breaking down of organic compounds, particularly simple carbohydrates like glucose, in the living cells, with the release of energy. The chief purpose of respiration is the production of energy for the activities of the body.

Question 108.
Mention two major types of respiration found in organisms.
Answer:
The two types of respiration are

• Aerobic respiration
• Anaerobic respiration.

Question 109.
What is aerobic respiration? Explain with the help of a chemical equation.
Answer:
The process of respiration which uses oxygen to break down organic molecules to produce energy is called aerobic respiration. During aerobic respiration, glucose undergoes oxidation in the body cells to form carbon dioxide and water. This process requires oxygen to burn glucose to produce energy.

Question 110.
What is anaerobic respiration? Explain. Write a chemical equation for it.
Answer:
The process of respiration that takes place without the use of oxygen is called anaerobic respiration. During anaerobic respiration, organic compounds break down into alcohol and carbon dioxide to produce energy.

Question 111.
Distinguish between aerobic respiration and anaerobic respiration.
Answer:
Aerobic respiration:

1. Oxygen is required for aerobic respiration.
2. Takes place in higher order organisms (eukaryotes).
3. Energy released is relatively more.
4. Carbon dioxide and water are the byproducts.

Anaerobic respiration:

1. Takes place in the absence of oxygen.
2. Takes place in lower order organisms such as bacteria (prokaryotes).
3. Energy released is relatively less.
4. Alcohol and carbon dioxide are the byproducts of this process.

Question 112.
Where exactly in the cell does respiration occur in eukaryotes?
Answer:
The site of respiration in eukaryotes is mitochondria.

Question 113.
Prokaryotes do not contain mitochondria. How is energy released in them?
Answer:
Compared to amoeba, there is an advanced system of respiration in cockroach. Amoeba respires through simple diffusion and there is no specialized structure for respiration. However, in cockroach, we find a specialized respiratory system.

Question 114.
What is the mechanism by which respiration takes place in amoeba?
Answer:
Respiration in amoeba takes place by the process of diffusion through body surface.

Question 115.
What is the respiratory system in cockroach called?
Answer:
The respiratory system in cockroach is called tracheal system.

Question 116.
Show by a diagram the respiratory system in cockroach. Label in the diagram spiracle and tracheal trunk.
Answer:

Question 117.
What are the major parts of the tracheal system (respiratory system) in cockroach?
Answer:
The tracheal system in cockroach has three major parts. They are spiracles, trachea and tracheoles.

Question 118.
Whal’ane spiracles in cockroach? How many of them are there in a cockroach?
Answer:
The respiratory openings found on the lateral side of the body of cockroach are called spiracles. There are 10 pairs of spiracles in a cockroach.

Question 119.
Where are the spiracles found on the body of a cockroach? What do these openings lead to?
Answer:
All spiracles are found on the lateral side of the body of a cockroach. There are 10 pairs of spiracles of which two pairs are found in the thoracic region and eight pairs in the abdominal region. Spiracles in cockroach lead to trachea which branches into tracheoles.

Question 120.
What is the mechanism by which carbon dioxide goes out of the body of cockroach and oxygen gets in? What is the role of blood in the transport of oxygen in cockroach?
Answer:
Carbon dioxide produced during respiration goes out directly from the body cells into the tracheal tubes by diffusion. From the tracheal tubes, carbon dioxide goes out to the surrounding medium through spiracles.

Similarly, oxygen from the surrounding atmosphere enters the tracheal tubes through spiracles. From the tracheal tubes, oxygen diffuses directly into the body cells. The blood of cockroach is called haemolymph. It has no role in oxygen transport.

Question 121.
Briefly describe the process of respiration in cockroach.
Answer:
Cockroach is an insect. Like all insects, cockroach breathes through a system of tubes called tracheal tubes. Each tracheal tube opens into spiracles present on the lateral side of the body. The valves of the spiracles open when the level of carbon dioxide in the insect rises to a high level.

Carbon dioxide diffuses out of the cell into the trachea and from there to the outside. Similarly, fresh oxygen diffuses in. The tracheal system brings air directly to all the cells through the tracheoles.

Question 122.
What is the chief organ of respiration in humans?
Answer:
The chief organ of respiration in humans are the lungs.

Question 123.
Is the respiration in humans aerobic or anaerobic? Why?
Answer:
Respiration in humans is aerobic. This is because respiration in humans requires oxygen.

Question 124.
List the major parts of human respiratory system.
Answer:
The respiratory system in humans consists of nose, pharynx, larynx, trachea, bronchi, bronchioles and lungs.

Question 125.
What is the role of nose in human respiratory system?
Answer:
Nose has a pair of nostrils that leads to the nasal cavity. It is lined with ciliated epithelium and mucous glands. The cilia and the mucous produced by the mucous glands will together trap dust, pollens and other materials.

Air is also moistened and warmed up by the epithelium of the nose. The nasal chamber is provided with a special pocket of sensory cells (olfactory epithelium), that respond to the stimuli of smell.

Question 126.
It is desirable to breathe through the nose. Give reason.
Answer:
Nose has ciliated (hairy) epithelium and mucous glands which produce mucous. This will help to trap dust, pollen and other undesirable particles that may be present in the inhaled air. Thus, the hairs in the nostrils and the mucous act as barrier to the entry of undesirable particles. Therefore, it is desirable to breathe through the nose.

Question 127.
What is trachea? What is the importance of C-shaped cartilaginous rings in it?
Answer:
The wind pipe in our body that extends from the larynx to the point it bifurcates into two branches is called trachea. C-shaped cartilaginous rings support the trachea, keep the trachea open all the time and prevent it from collapsing. This enables continuous flow of air in and out of the lungs.

Question 128.
What are bronchi and bronchioles?
Answer:
The trachea divides itself into main branches called bronchi. One of them goes to the right lung and the other to the left lung. Each bronchus (singular of bronchi) divides further into a number of small branches called bronchioles. The finest branch of each bronchiole ends in structures called alveoli.

Question 129.
What are alveoli? What is their function?
Answer:
The trachea has two bronchi and each bronchus leads to one of the lungs. Each bronchus divides into a large number of branches and sub-branches called bronchioles. Each bronchiole ends in a cluster of small microscopic bubble-like sacs called alveoli.

Alveoli are the sites where gas exchange takes place. Oxygen present in the alveoli will diffuse into the blood capillaries and the carbon dioxide present in the blood will diffuse to the alveoli.

Question 130.
How does the oxygen present in the lungs get into the blood stream?
Answer:
The lungs have a large network of bronchioles. Each bronchiole ends in a cluster of air sacs called alveoli. Each alveolus is surrounded by a network of blood capillaries. The exchange of gases takes place between alveoli and the blood in the surrounding capillaries by the process of diffusion. Oxygen in the alveoli diffuses into the blood through the alveolar wall. Carbon dioxide present in the blood diffuses into the alveoli.

Question 131.
Draw a neat diagram of the respiratory system in humans and label the parts.
Answer:

Question 132.
Describe briefly the process of respiration in human beings.
Answer:
During breathing, we take in oxygen-rich air. When we inhale, air enters our body through the nostrils. The nasal cavity is lined with a ciliated mucous membrane which filters, warms, and moistens the air. The filtered air moves to the pharynx and then is directed to the trachea.

Air moves into the lungs through bronchi and bronchioles and eventually reaches the alveoli located at the dead end of each bronchiole. Alveoli are surrounded by a network of capillaries through which blood will be circulating. The exchange of gases takes place at the alveoli.

Oxygen gets into the blood stream and carbon dioxide into the alveoli. Oxygen is carried by the blood to each of the living cells of the body. The oxidation of glucose takes place in the body cells which produce energy required for the bodily activities.

Question 133.
What is cellular respiration?
Answer:
Blood circulating around the alveoli gives out carbon dioxide and collects oxygen. Oxygenated blood distributes oxygen to the cells which is used for oxidizing glucose. This process is called cellular respiration.

Multiple Choice Questions

Question 1.
The process of obtaining food and utilizing it in the body is
(a) respiration
(b) nutrition
(c) excretion
(d) Reproduction
Answer:
(b) nutrition

Question 2.
Which of the following is a product of photosynthesis?
(a) starch
(b) fructose
(c) maltose
(d) Sucrose
Answer:
(a) starch

Question 3.
Insectivorous plants commonly grow in areas where soil is deficient in
(a) carbon
(b) nitrogen
(c) potassium
(d) Phosphorous
Answer:
(b) nitrogen

Question 4.
A person applies hydrogen peroxide on his wound. This is to kill
(a) aerobic bacteria
(b) fungi
(c) anaerobic bacteria
(d) protozoa
Answer:
(c) anaerobic bacteria

Question 5.
The gas liberated during photosynthesis is
(a) nitrogen
(b) hydrogen
(c) carbon dioxide
(d) oxygen
Answer:
(d) oxygen

Question 6.
Green plants are
(a) autotrophs
(b) parasites
(c) saprotrophs
(d) heterotrophs
Answer:
(a) autotrophs

Question 7.
The nutrient obtained by insectivores from insects is
(a) fats
(b) carbon
(c) nitrogen
(d) Starch
Answer:
(c) nitrogen

Question 8.
Lichen is a combination of
(a) fungi and insectivore
(b) fungi and diatoms
(c) algae and fish
(d) algae and fungi
Answer:
(d) algae and fungi

Question 9.
The digestive juice that does not contain any enzyme is
(a) bile juice
(b) gastric juice
(c) intestinal juice
(d) pancreatic juice
Answer:
(a) bile juice

Question 10.
Amylase converts starch into
(a) glucose
(b) sucrose
(c) lactose
(d) maltose
Answer:
(d) maltose

Question 11.
The respiratory system is made up of trachea, the lungs, and the
(a) liver.
(b) diaphragm.
(c) oesophagus.
(d) pancreas
Answer:
(b) diaphragm.

Question 12.
The opening to the trachea is covered by a small flap of tissues called
(a) Glottis
(b) Trachea
(c) Epiglottis
(d) Larynx
Answer:
(c) Epiglottis

Question 13.
The digestion of food in human beings starts in
(a) the mouth and ends in the large intestine
(b) the mouth and ends in the small intestine
(c) the stomach and ends in the anus
(d) the stomach and ends in the large intestine
Answer:
(b) the mouth and ends in the small intestine

Question 14.
Another name for the windpipe is
(a) Trachea
(b) Lungs
(c) Larynx
(d) Oesophagus
Answer:
(a) Trachea

Question 15.
Which of the following raw materials is available in the air for photosynthesis?
(a) Oxygen
(b) Carbon dioxide
(c) Nitrogen
(d) Hydrogen
Answer:
(b) Carbon dioxide

Question 16.
The swallowed food moves downwards in the alimentary canal because of
(a) force provided by the muscular tongue
(b) the flow of water taken with the food
(c) gravitational pull
(d) the contraction of muscles in the wall of food pipe.
Answer:
(d) the contraction of muscles in the wall of food pipe.

Question 17.
An enzyme that acts only in acidic medium is
(a) pepsin
(b) lipase
(c) trypsin
(d) Amylase
Answer:
(a) pepsin

Question 18.
Which is the first enzyme to mix with food in the digestive tract?
(a) pepsin
(b) cellulase
(c) salivary amylase
(d) Trypsin
Answer:
(c) salivary amylase

Question 19.
The region of the digestive system, where no digestion occurs is
(a) ileum
(b) stomach
(c) mouth
(d) oesophagus
Answer:
(d) oesophagus

Question 20.
Autotrophic organisms include
(a) bacteria and virus
(b) bacteria and fungi
(c) green plants and some bacteria
(d) green plants and all bacteria
Answer:
(c) green plants and some bacteria

Question 21.
Which of the following parts in the human respiratory system is commonly called wind pipe?
(a) trachea
(b) larynx
(c) nasal passage
(d) nose
Answer:
(a) trachea

Question 22.
The blood of cockroach is called haemolymph because
(a) it is a mixture of lymph and blood
(b) it is lymph functioning as blood
(c) it does not contain red blood corpuscles
(d) it flows in definite blood vessels.
Answer:
(c) it does not contain red blood corpuscles

Question 23.
Which activity of amoeba is illustrated in the diagram shown here?

(a) ingestion
(b) digestion
(c) egestion
(d) assimilation
Answer:
(a) ingestion

Fill In The Blanks

• The digestion of food in humans begins in the mouth
• The chief organ of respiration in humans is lungs
• The exchange of gases in amoeba takes place by diffusion
• The wind pipe is also called trachea
• Millions of air sacs found at the end of bronchioles in human lungs are called alveoli
• Carbon dioxide enters the plant body through stomata
• Light dependent/Light reaction takes place in the grana of chloroplast.
• The reaction that takes place in the stroma of chloroplast is light independent/dark reaction.
• The chemical energy released during light dependent reaction is used to produce starch during light independent reaction,
• The group of photosynthetic plants that obtain nitrogen by trapping and digesting insects are called insectivorous plants
• E.Coli bacteria provide us B-complex vitamins.
• The human digestive tract is also known as alimentary canal
• Saliva makes food into a soft paste called bolus
• Salivary amylase in saliva converts starch into maltose.
• Pharynx is the common passage for both food and air in humans.
• The tissue that prevents bolus from entering into the wind pipe is epiglottis
• Respiration in amoeba takes place by diffusion through body surface

Match The Following

A	B
1. Stomach	a.  Bile juice
2.  Liver	b.  Reabsorption of water
3.  Small intestine	c.  Saliva secretion
4. Large intestine	d. Acid release
	e. Throws out faece
	f. Pancreatic juice
	g. Absorption of digested foo

Answer:
1 – d, 2 – a, 3 – g, 4 – b.

A	B
1. Amylase	a. helps in the digestion of fats
2. Pepsin	b. converts starch into maltose
3. Rennin	c. Breaks down proteins into simpler molecules
4. Lipase	d. Converts sucrose into glucose
5. Sucras	e. Converts glucose into sucrose
	f. Breaks down milk proteins

Answer:
1 – b, 2 – c, 3 – f, 4 – a, 5 – d.