KSEEB Class 10 Science Important Questions Chapter 6 Life Processes

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Karnataka SSLC Class 10 Science Important Questions Chapter 6 Life Processes

Question 1.
What is a living being?
Answer:
An individual form of life that consists of a single cell or a complex of cells in which cell organelles or organs work together to carry out the various basic processes of life is called a living being.

Question 2.
List the characteristics of living beings.
Answer:
The following are the characteristics of living beings:

1. Living beings are made up of a cell or cells.
2. They obtain and use energy to survive.
3. They have the unique ability to reproduce, ability to grow, ability to metabolize, ability to respond to stimuli, ability to adapt to the environment, ability to move and an ability to respire.

Question 3.
Are viruses living beings? Explain.
Answer:
Viruses show the characteristics of both living and non-living things. They become active and reproduce only when they are inside a host cell. They show the characteristics of non-living things when they are outside the host cell. Therefore, there is a debate whether they are living beings or not. It is because of this dual nature viruses are considered as a connecting link between the living and the non-living.

Question 4.
What are life processes? Name some of the basic life processes.
Answer:
The basic activities that take place in the body of organisms, which keep them alive and help to maintain their body are known as life processes. The basic life processes include nutrition, respiration, transport, digestion, excretion, reproduction etc.

Question 5.
What criteria do we use to decide whether something is alive?
Answer:
Any visible movement such as walking, breathing, or growing is generally used to decide whether something is alive or not. However, a living organism can also have movements that are not visible to the naked eye. The presence of life processes in the body helps us decide whether something is alive or not.

Question 6.
What processes would you consider essential for maintaining life?
Answer:
The processes that perform the maintenance function of living organisms are called life processes. All life processes such as nutrition, respiration, transportation, excretion, control and coordination are essential for maintaining life.

Question 7.
Why do organisms especially animals need an outside source of energy?
Answer:
Most organisms especially animals will have to carry out basic maintenance processes in their body to prevent damage and breakdown. This requires energy. Since animals cannot prepare their own food, the source of energy must come from outside the body of the individual organism. So there must be a process to transfer a source of energy from outside the body of the organism. This source of energy is called food.

Nutrition

Question 8.
What is nutrition?
Answer:
The process of taking in food and using it for growth, metabolism, and repair by organisms is known as nutrition.

Question 9.
Which are the two major types of nutrition found in organisms?
Answer:
Organisms are classified into two major groups on the basis of their nutrition. The two groups are:

1. Autotrophic nutrition, and
2. Heterotrophic nutrition.

Question 10.
What is autotrophic mode of nutrition? Give an example for organisms having this type of nutrition.
Answer:
The kind of nutrition in which the organisms prepare their own organic food by utilising only the inorganic raw materials present in the surroundings is known as autotrophic mode of nutrition.

For example, green plants synthesize their own food from carbon dioxide and water. Therefore, green plants are autotrophs.

Question 11.
What are autotrophs?
Answer:
Organisms such as green plants, which synthesize their own food, are called autotrophs.

Question 12.
What is heterotrophic mode of nutrition?
Answer:
The mode of nutrition in which the organisms depend on other organisms for their food and survival is known as heterotrophic mode of nutrition.

Question 13.
Name the process that fulfils the energy needs of autotrophs.
Answer:
A process called photosynthesis fulfills the energy needs of autotrophic organisms. During this process, the autotrophs utilise inorganic materials available in the environment and convert them into stored forms of energy.

Question 14.
What is photosynthesis?
Answer:
The process by which green plants and some other organisms use sunlight to synthesize nutrients from carbon dioxide and water is called photosynthesis.

Question 15.
What is the chief product and by-product of photosynthesis?
Answer:
The chief product of photosynthesis is carbohydrate. The by-product of photosynthesis is oxygen.

Question 16.
What do green plants heed from the outside environment for the synthesis of carbohydrates?
Answer:
Green plants need sunlight, carbon dioxide and water from the environment for the synthesis of food (carbohydrates).

Question 17.
How are the carbohydrates synthesized during photosynthesis useful to plants?
Answer:
The carbohydrates synthesized by green plants is utilised for providing energy to the plant.

Question 18.
What happens to carbohydrates in green plants, which are not immediately utilized?
Answer:
The carbohydrates, which are not used immediately by green plants, are stored in the form of starch. The stored starch serves as the internal energy reserve to be used as and when required by the plant.

Question 19.
Write a balanced chemical equation for the reaction that occurs in photosynthesis.
Answer:
Green plants trap sunlight with the help of chlorophyll and use this energy to convert carbon dioxide and water into carbohydrates. This can be represented by the equation given below:

Question 20.
Which are the three major events that happen during the process of photosynthesis?
Answer:
The following three events occur during photosynthesis:

1. Absorption of light energy by chlorophyll present in the plant.
2. Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.
3. Reduction of carbon dioxide to carbohydrates.

Question 21.
Single celled organisms do not require specific organs for taking in food, exchange of gases or removal of wastes etc. Justify this statement.
Answer:
In single-celled organisms, the entire surface of the organism is in direct contact with the environment. Therefore, they do not require specific or specialized organs for taking in food, exchange of gases or removal of wastes from their body. These happen by simple processes like diffusion, which do not need specific organs.

Question 22.
What are chloroplasts? What do they contain? What is their role in photosynthesis?
Answer:
A cross-section of a leaf, when observed under a microscope, shows up some cells containing a type of organelle in the form of green dots. These green dots are cell organelles called chloroplasts. Chloroplasts contain a green coloured pigment called chlorophyll. Chlorophyll traps sunlight and facilitates photosynthesis.

Question 23.
What is the site of photosynthesis in green plants?
Answer:
Photosynthesis does not take place in all the cells of green plants. It occurs only in those cells which possess the green coloured plastids called chloroplasts. Chloroplasts are the sites of photosynthesis in green plants.

Question 24.
Show by an experiment that chlorophyll is essential for photosynthesis.
Answer:
Take a potted croton plant or any other plant having variegated leaves. Keep the plant in a dark room for three days so that all the starch gets used up. Now keep the plant in sunlight for about six hours. Pluck a leaf from the plant.

Mark the green areas in it and trace them on a sheet of paper. Dip the leaf in boiling water for a few minutes. After this, immerse it in a beaker containing alcohol. Carefully place this beaker in a water-bath and heat till the alcohol begins to boil.

The leaf gets decolourized. Take the leaf out and dip it in boiled water. Now the leaf becomes soft. Take the leaf out and stain it with iodine solution. The blue colour appears in only those parts of the leaf that were green in colour.

The blue colour does not appear in variegated parts. This shows the formation of starch in only chlorophyll-containing parts of the leaf. This demonstrates that chlorophyll is essential for photosynthesis.

Question 25.
Where do plants set the raw materials required for photosynthesis?
Answer:
For photosynthesis, plants obtain the following raw materials:

1. Water: Generally plants obtain water from the roots. Roots absorb it from the soil.
2. Carbon dioxide: Plants obtain carbon dioxide from the atmosphere. Tiny openings called stomata located on the leaves, allow the carbon dioxide gas to enter into the plant directly from the atmosphere.
3. Chlorophyll: It is already present in the leaves.
4. Sunlight: Plants obtain sunlight from the sun.

Question 26.
Draw a neat, labelled diagram of the cross section of a leaf.
Answer:

Question 27.
Draw neat, labelled diagrams showing the stomata with pore open and pore closed.
Answer:

Question 28.
How do green plants obtain carbon dioxide for photosynthesis?
Answer:
Green plants that grow on land take carbon dioxide directly from the atmosphere. Carbon dioxide enters the leaves through tiny pores present in the epidermal layers. These pores are called stomata.

Each stoma is guarded by two kidney-shaped guard cells. The guard cells regulate the opening and closing of the stomatal pore. The plant closes these pores when it does not need carbon dioxide for photosynthesis. The guard cells swell when water flows into them, causing the stomatal pore to open. Similarly the pore closes if the guard cells shrink.

Question 29.
How do the guard cells regulate the process of opening and closing of stomatal pores?
Answer:
Opening and closing of stomata occur due to the changes in the turgor pressure of the guard cells. When guard cells are turgid, stomatal pores are open, while in flaccid form, the stomatal pores are closed.

Question 30.
What are the necessary conditions for autotrophic nutrition and what is its by-product?
Answer:
The following conditions are necessary for autotrophic nutrition:

1. Availability of sunlight
2. Presence of chlorophyll in the organism
3. Availability of carbon dioxide and water
4. Optimal conditions of temperature.

The by-product of autotrophic nutrition is molecular oxygen (O₂).

Question 31.
With the help of an experiment show that carbon dioxide is necessary for photosynthesis.
Answer:

Experimental set-up (a) with potassium hydroxide, (b) without potassium hydroxide Take two healthy potted plants, which are nearly the same size. Keep them in dark for three days. Now place each plant on separate glass plates. Place a watch-glass containing potassium hydroxide by the side of one of the plants. Potassium hydroxide has the property to absorb carbon dioxide.

Cover both plants with separate bell-jars as shown in the figure. Use vaseline to seal the bottom of the jars to the glass plates so that the set-up is airtight. Keep the plants in sunlight for about two hours.

Pluck a leaf from each plant and check for the presence of starch. The leaf of the plant which got carbon dioxide turns blue showing that synthesis of starch has taken place. The leaf of the plant, which did not get carbon dioxide, remains colourless showing the absence of starch. This shows that carbon dioxide is necessary for photosynthesis.

Question 32.
How do plants get water for photosynthesis?
Answer:
In terrestrial plants, the water required for photosynthesis is taken up from the soil by the roots.

Question 33.
How do terrestrial plants get materials like nitrogen, phosphorus, iron and magnesium?
Answer:
Terrestrial plants get materials like nitrogen, phosphorus, iron and magnesium from the soil.

Question 34.
Why is nitrogen essential for plants? How do plants get nitrogen?
Answer:
Nitrogen is an essential element used in the synthesis of proteins and other compounds. This is taken up from the soil in the form of inorganic nitrates or nitrites. Some plants take nitrogen in the form of organic compounds, which have been prepared by bacteria from atmospheric nitrogen.

Question 35.
What are heterotrophs? Give examples.
Answer:
Organisms that cannot synthesize their own food and hence depend on other organisms for their food either directly or indirectly are called heterotrophs.
E.g.: Cow, tiger, butterfly, fish, etc.

Question 36.
Mention some of the strategies by which the food is taken in and used by heterotrophic organisms.
Answer:
Some heterotrophic organisms break down the food material outside their body and then absorb it. Organisms like bread moulds, yeast and mushrooms obtain their nutrition in this way. Some other heterotrophic organisms take in whole material and break it down inside their bodies.

What can be taken in and broken down depends on the body design and functioning. A few other organisms derive nutrition from plants or animals without killing them. This parasitic nutritive strategy is used by a wide variety of organisms like cuscuta, ticks, lice, leeches and tapeworms.

Question 37.
Name the following:

1. The process in plants that links light energy with chemical energy,
2. Organisms that can make their own food,
3. The cell organelle in plants where photosynthesis occurs,
4. Cells that surround the pore of a stomata,
5. Organisms which cannot make their own food,
6. The enzyme produced by gastric glands that act on proteins.

Answer:

1. Photosynthesis
2. Autotrophs
3. Chloroplasts
4. Guard cells
5. Heterotrophs
6. Pepsin.

Question 38.
Describe the mode of nutrition in amoeba.
Answer:

Amoeba is a unicellular organism. Amoeba ingests the food by encircling it using finger-like extensions of the cell surface, which fuse over the food particle forming a food vacuole. Inside the food vacuole, complex substances are broken down into simpler ones, which then diffuse into the cytoplasm. The remaining undigested material is moved to the surface of the cell and thrown out.

Question 39.
Explain briefly the nutrition in paramecium.
Answer:
Paramecium is a single-celled organism. Paramecium has tiny hairs called cilia all over the body. Paramecium has a definite shape and food is taken in at a specific spot. Food is moved to this spot by the movement of cilia, which cover the entire surface of the cell.

The food is ingested with a little surrounding water to form a food vacuole. The food is digested with the help of enzymes. The digested food is absorbed directly into the cytoplasm by diffusion. The undigested food is expelled out through anal pore.

Question 40.
What is the function of the human digestive system?
Answer:
Human beings ingest a variety of foods, which can be classified by their nutrition content as carbohydrates, lipids and proteins. The human digestive system is responsible for the processing and uptake of nutrition. In the process of digestion, the complex organic molecules arc broken down into simple molecules.

Question 41.
Where does the digestion of food begin in the human body?
Answer:
The digestion of food in human beings begins in the mouth.

Question 42.
The digestion of food in human beings begins in the mouth. Explain this statement.
Answer:
Digestion of food in humans beings begins in the mouth with the help of the teeth, tongue and salivary glands. When we chew our food, it is broken down into smaller pieces by our teeth.

The salivary glands release saliva, and with the help of the tongue the saliva is mixed in with the chewed food. Saliva helps move the food to the back of the mouth and it also contains chemicals to break down some sugars. Once the food is swallowed, it moves down the oesophagus.

Question 43.
What is saliva? What is its function?
Answer:
The watery fluid that is secreted into the mouth by the salivary glands is called saliva.
Saliva provides lubrication for chewing and swallowing. The wetting of food by the saliva helps easy movement into the oesophagus. The enzyme amylase present in saliva helps in partial digestion of carbohydrates (starch).

Question 44.
What is the role of saliva in the digestion of food?
Answer:
The digestive functions of saliva include moistening the food and helping to create a food bolus. Saliva contains the enzyme amylase. This is also called ptyalin. This enzyme breaks down starch into simpler sugars such as maltose and dextrin that can be further broken down in the small intestine. Thus saliva helps in the partial digestion of carbohydrates.

Question 45.
How do you show the action of saliva on starch?
Answer:
Take 1 mL of 1% starch solution in two separate test tubes A and B. Add 1 mL of saliva to test tube A and leave both test tubes undisturbed for 20-30 minutes. Now add a few drops of dilute iodine solution to the test tubes and observe the changes. The contents of test tube B turn blue indicating the presence of starch. The colour of the contents in A however does not change. This indicates that saliva has degenerated starch into simpler molecules.

Question 46.
What is alimentary canal in human beings?
Answer:
The alimentary canal in human beings is basically a long tube that extends from the mouth to the anus. It is the tube through which food passes through the body from mouth to anus during digestion.

Question 47.
Draw a neat, labelled diagram of the human alimentary canal (human digestive system).
Answer:

• Oesophagus – Food pipe; the part that transports food from mouth to stomach
• Gall bladder – The part that stores bile
• Liver – The part that produces bile juice
• Pancreas – The part that secretes pancreatic juice containing the enzymes trypsin and lipase
• Stomach – The part that stores and chums food
• Small intestine – Site of complete digestion of carbohydrates, proteins and fats; the part that receives secretions of liver and pancreas
• Large intestine (Colon) – The part that stores waste
• Anus – Opening for waste elimination; the part that removes unabsorbed matter from the body

Question 48.
What is peristalsis? How is it useful? the body
Answer:
The rhythmic involuntary movement of the muscles in the walls in the digestive tract, which create wave-like movements is called peristalsis.
Peristaltic movements help to push the food materials and waste through the alimentary canal.

Question 49.
Mention the major parts of the human digestive system.
Answer:
The major parts of the human digestive system are the mouth, salivary glands, pharynx, oesophagus, stomach, small intestine, large intestine, rectum and the accessory digestive glands such as liver, gall bladder, and pancreas.

Question 50.
What is oesophagus? What are its functions?
Answer:
The part of the alimentary canal that extends from the throat to the stomach in the form of a muscular tube is called oesophagus.

Oesophagus carries swallowed masses of chewed food along its length and pushes it to the stomach with the help of peristaltic movements.

Question 51.
What is stomach? Mention its functions.
Answer:
The sac-like organ in the digestive system located on the left side of the body behind the lower rib cage and which receives chewed food from the oesophagus is called stomach.
The following are the functions of stomach:

1. It holds the food that comes from the oesophagus.
2. It initiates the digestion of proteins.
3. It produces acids, which will kill bacteria that may be present in the food.
4. It converts the food into chyme and pushes it to the small intestine.

Question 52.
Which part of our digestive system releases an enzyme called pepsin? What is its function?
Answer:
Gastric glands located on the wall of the stomach release an en2yme called pepsin. The enzyme pepsin helps in the digestion of proteins. ~

Question 53.
Explain the digestive function of the stomach.
Answer:
Digestion in stomach is taken care of by the gastric glands present in the wall of the stomach. Gastric glands release hydrochloric acid, a protein-digesting enzyme called pepsin, and mucus. Hydrochloric acid creates an acidic medium, which facilitates the action of the enzyme pepsin and also kills bacteria that may be present in the food.

Proteins are long chains of amino acids. The enzyme pepsin hydrolyzes proteins into fragments of various sizes called peptides. The mucus protects the inner lining of the stomach from the action of the acid under normal conditions.

Question 54.
What happens if the gastric glands located on the walls of the stomach do not secrete mucus?
Answer:
Gastric glands located on the walls of the stomach produce hydrochloric acid, mucus and digestive enzymes. The mucus produced will protect the inner lining of stomach from corrosion by hydrochloric acid. The absence of mucus will corrode the lining of the stomach and may lead to gastric ulcers.

Question 55.
What is small intestine? What are its functions?
Answer:
The part of the alimentary canal between stomach and colon is called small intestine. It is a long coiled tube where digestion of all major components of our food gets completed and the nutrients from the digested food are absorbed and delivered into the bloodstream.

Question 56.
Compare the length of the small intestine in herbivores and carnivores.
Answer:
The length of the small intestine in animals differs depending on the food they eat. Herbivores that feed on grass have a longer small intestine to allow for the digestion of cellulose. Meat is easier to digest. Therefore, carnivores like tigers have a shorter small intestine.

Question 57.
Why is the small intestine in herbivores longer than in carnivores?
Answer:
Herbivores feed on plant matter that is rich in cellulose. The digestion of cellulose takes longer time. Meat is easier to digest. This is why herbivores have a longer small intestine while carnivores have relatively shorter small intestine.

Question 58.
How is the small intestine designed to absorb digested food?
Answer:
The small intestine in humans is a long tubular structure. The inner lining of the small intestine has numerous finger-like projections called ‘villi’. These structures increase the surface area for absorption and facilitate the digested food to enter into the bloodstream.

Question 59.
In human alimentary canal, name the site of complete digestion of various components of food.

OR

Mention the site of complete digestion of carbohydrates, proteins and fats in humans.
Answer:
Complete digestion of various components of food takes place in the small intestine.

Question 60.
What is bile juice? What is its function?
Answer:
A digestive juice produced by the liver, which gets stored and concentrated in the gall bladder, is known as bile juice.

The food coming from the stomach is acidic and has to be made alkaline for the pancreatic enzymes to act. Bile juice from the liver accomplishes this in addition to acting on fats. Bile juice assists in the digestion of lipids (fats).

Question 61.
How does bile juice help in the digestion offats?
Answer:
Fats are present in the intestine in the form of large globules, which makes it difficult for enzymes to act on them. Bile juice enables in increasing the efficiency of enzyme action on fat. Bile juice contains bile salts, which break the fat globules into smaller globules. This emulsifying action of bile salts breaks down fats into small particles.

Question 62.
How are fats digested in our body? Where does this process take place?
Answer:
Fats are digested inside the small intestine. When partly digested and acidic food enters into the small intestine from the stomach, bile juice from the liver and the enzyme lipase present in the pancreatic juice get mixed with it. Certain salts present in bile emulsify the fat molecules into small globules. The enzyme lipase brings about the digestion of fat.

Question 63.
Why is the emulsification of fats important in the digestion of fats?
Answer:
Fats are very large molecules and the fat-digesting enzyme namely ‘lipase’ produced by the pancreas cannot act efficiently on such large molecules. The bile salts present in bile juice act on large fat molecules and break them down into smaller globules by emulsifying them. This facilitates the easy action of lipase on fat globules and their digestion.

Question 64.
What is pancreatic juice? Name two enzymes present in it. What is its function?
Answer:
The digestive juice secreted by the pancreas is called pancreatic juice. Pancreatic juice contains enzymes such as trypsin and lipase. Trypsin helps in the digestion of proteins and lipase helps in the breaking down of emulsified fats.

Question 65.
What is intestinal juice? What is its function?
Answer:
The watery digestive secretions by the glands lining the small intestine walls are known as intestinal juice. The enzymes present in the intestinal juice help to convert

1. Proteins to amino acids,
2. Complex carbohydrates into glucose, and
3. Fats into fatty acids and glycerol.

Question 66.
What are the final products obtained after the digestion of carbohydrates and proteins?
Answer:
Glucose and amino acids are the final products obtained after digestion of carbohydrates and proteins respectively.

Question 67.
Small intestine is called the site of complete digestion. Why?
Answer:
The process of breaking down of each of the major components of our food into simple molecules gets completed in the small intestine. Hence, small intestine is considered as the site of complete digestion.

Question 68.
Explain the process of digestion in the small intestine of man.
Answer:
The food in the stomach is passed on to the small intestine. The small intestine is where most chemical digestion occurs. Here, the bile juice produced by the liver and pancreatic juice produced by the pancreas and intestinal juice produced by the glands on the walls of the small intestine mix with the food.

The bile salts present in bile juice emulsify the fats and facilitate their digestion by the enzymes produced by the pancreas. Pancreatic juice contains enzymes that help to break down carbohydrates, fats and proteins.

Intestinal juice will also facilitate the digestion of food. In this process, carbohydrates are converted into glucose, proteins are turned into amino acids and, lipids are converted into simple fatty acids. Digested food is absorbed by the villi present in the walls of the intestine. Thus the process of digestion gets completed in the small intestine.

Question 69.
What are villi? What is their function?
Answer:
The numerous and tiny finger-like projections of the inner lining of the small intestine are known as villi. Villi actually increase the surface area for absorption of digested food. They absorb the digested food and let it into the bloodstream.

Question 70.
What happens to the undigested food in our body?
Answer:
The unabsorbed food is sent into the large intestine. The inner wall of the large intestine also contains villi. It absorbs water present in the undigested food. The rest of the material is removed from the body via the anus. The anal sphincter regulates the exit of this waste.

Question 71.
Briefly describe the digestion of food in human beings.
Answer:
The digestion of food begins in the mouth. When we chew food, both mechanical and chemical digestion occurs. The saliva produced by the salivary glands contains an enzyme called ptyalin. This enzyme converts starch present in food into smaller molecules (maltose).

When we swallow, the chewed food goes to the stomach through the oesophagus with the help of peristaltic movements. The stomach stores the food temporarily and mixes the food by muscular action. The glands present in the stomach lining produce hydrochloric acid (HCl) and an enzyme called pepsin that digests protein.

The food in the stomach is then passed on to the small intestine. The small intestine is where most chemical digestion occurs. Here, the bile juice produced by the liver, pancreatic juice produced by the pancreas and intestinal juice produced by the glands on the walls of the small intestine mix with the food.

The bile salts present in bile juice emulsify the fats and facilitate their digestion by the enzymes produced by the pancreas. Pancreatic juice contains enzymes, which help to break down carbohydrates, fats and proteins.

Intestinal juice will also facilitate the digestion of food. In this process, carbohydrates are converted into glucose, proteins are turned into amino acids and lipids are converted into simple fatty acids. Thus the process of digestion gets completed in the small intestine.

The wall of the small intestine has tiny finger-like structures called villi They help to absorb the digested food and let it into the bloodstream.

The undigested food is moved to the large intestine. The villi present on the walls of the large intestine absorb the water present in the undigested food. Then the undigested food is thrown out of the body periodically through the anus.

Question 72.
Name the organ that secretes the following enzymes:

1. Ptyalin,
2. Trypsin,
3. Pepsin.

Answer:

1. The enzyme Ptyalin is produced by the salivary glands in the mouth.
2. The enzyme Trypsin is produced by the pancreas.
3. The enzyme Pepsin is produced in the stomach.

Question 73.
Why does an organism use outside raw materials?
Answer:
Organisms use outside raw materials for maintenance and sustenance of life.

Question 74.
What are outside raw materials used for by an organism?
Answer:
Raw materials are substances that cannot be directly utilized by the organisms. They require further processing inside the body like digestion in animals and photosynthesis in plants. CO₂, water and mineral compounds are raw materials for plants while water, carbohydrates, proteins, fats and vitamins are raw materials for the animals. These raw materials are to be taken from outside by plants and animals respectively.

Question 75.
What are the differences between autotrophic nutrition and heterotrophic nutrition?
Answer:

Autotrophic Nutrition	Heterotrophic Nutrition
1. Organism can manufacture its own food. Food is made from inorganic components.	Organism cannot manufacture its own food. Food is obtained by consuming organic components.
2. Chlorophyll and sunlight are required.	Chlorophyll and sunlight are not required.
3. Photosynthesis or chemosynthesis takes place.	The organisms get food by consuming other organisms directly or indirectly.
4. It occurs in green plants and some bacteria.	It occurs in animals and insectivorous plants.

Question 76.
What is the role of the acid in our stomach?
Answer:
The walls of our stomach produce hydrochloric acid (HC1). This acid present in our stomach makes the medium acidic. This facilitates the action of the enzyme pepsin. The acidic medium in the stomach will also help to kill the bacteria ingested with food.

Question 77.
What is the function of digestive enzymes? Name the digestive juice that does not contain any enzymes.
Answer:
Digestive enzymes act on the complex food molecules and break them into simpler components. They thus facilitate the process of digestion of food.

[For example, amylase (ptyalin) present in saliva helps to break down starch into maltose. The enzyme pepsin produced by the glands on the lining of the stomach helps to break down proteins.

The enzyme trypsin present in the pancreatic juice helps in the digestion of proteins while lipase helps in breaking down of emulsified fats. Pancreatic amylase helps to break down carbohydrates into simple sugars.]. Bile juice produced by the liver does not contain any digestive enzymes.

Question 78.
What is the function of anal sphincter?
Answer:
The anal sphincter regulates the exit of faecal matter from the anus.

Respiration

Question 79.
What is respiration? What is its chief purpose?
Answer:
A process in living organisms involving the production of energy, typically with the intake of oxygen and the release of carbon dioxide from the oxidation of complex organic substances is known as respiration. The chief purpose of respiration is production of energy for bodily activities.

Question 80.
Distinguish between breathing and respiration.
Answer:
Breathing is the physical process of getting oxygen into the lungs and carbon dioxide out of the lungs. It allows for gas exchange to take place so that oxygen can be absorbed from the lungs into the blood and carbon dioxide is removed from the blood and breathed out from the lungs. This is also known as external respiration.

Respiration is the biochemical process during which release of energy takes place by the breakdown of glucose in living cells. Respiration takes place in every living cell and all cells need to respire to produce the energy they need. This is also known as internal respiration.

Question 81.
How can you establish that exhaled air contains carbon dioxide?
Answer:
Take some freshly prepared limewater in a test tube. Blow air through the limewater. Note how long it takes for the limewater to turn milky. Use a syringe to pass air through the same amount of fresh limewater taken in another test tube.

Note how long it takes for this limewater to turn milky. The limewater in the test tube into which we blow air from the mouth turns milky quickly than the other into which air is blown from a syringe. This shows that exhaled air is rich in carbon dioxide gas.

Question 82.
What are the different ways in which elucose is oxidised to provide energy in various organisms?
Answer:
The utilisation of glucose for the production of energy depends upon the availability of oxygen. Some organisms use oxygen to derive energy by breaking down glucose into carbon dioxide and water. This is known as aerobic respiration. Other organisms derive energy by breaking down glucose in absence of oxygen. This is known as anaerobic respiration.

Question 83.
Explain the various major pathways in which glucose is oxidised to produce energy in our body.

OR

Explain the breakdown of glucose in aerobic respiration and anaerobic respiration.
Answer:
Production of energy by breaking down of glucose can occur in three different ways,
(a) Our body cells use oxygen to break down glucose into carbon dioxide and water. This is aerobic respiration.

(b) Sometimes our body cells can use a pathway that does not involve sufficient amount of oxygen.

(c) Some organisms break down glucose in the absence of oxygen. In all the three cases, the first step is to break down glucose molecule into pyruvate. Glucose is a molecule with six carbon atoms. It is broken down into a molecule with three carbon atoms. This molecule is called pyruvate. This process takes place in the cytoplasm.

Question 84.
Show by a diagram the various pathways by which glucose breaks down in the cells.
Answer:

Question 85.
When will lactic acid build-up take place in our muscles? What is its consequence?

OR

Under what condition is lactic acid produced in the muscle cells?
Answer:
Sometimes the active muscles in our body get insufficient oxygen. In this condition, the pyruvate produced by the breakdown of glucose is converted into lactic acid. This causes the building-up of lactic acid in the active muscles.

Lactic acid is produced when there is lack of oxygen in the muscle cells. Excessive build-up of lactic acid in our muscles causes cramps.

Question 86.
Name the intermediate and end products of breakdown of glucose in aerobic respiration.
Answer:
Intermediate products: Pyruyic acid + Energy
End products: CO₂ + H₂O + Energy.

Question 87.
Give an example for anaerobic respiration.
Answer:
The fermentation of glucose into carbon dioxide and alcohol, which occurs in absence of oxygen, is an example for anaerobic respiration.

Question 88.
Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms like humans?
Answer:
Unlike the unicellular organisms, the multi-cellular organisms have complex body structures with specialized cells and tissues to perform various necessary functions of the body. Since these cells are not in direct contact with the surrounding environment, diffusion cannot meet the oxygen requirement of all these cells as diffusion is a very slow process.

Question 89.
Describe an experiment to show that the process of fermentation of sugar releases carbon dioxide.
Answer:
Take some fruit juice or sugar solution in a beaker and add some yeast to it. Take this mixture in a test tube fitted with a one-holed cork. Fit the cork with a bent glass tube. Dip the free end of the glass tube into a test tube containing freshly prepared limewater.

Leave it for a few hours. Gradually the limewater turns milky showing that fermentation of sugar produces carbon dioxide. In this process, fermentation of sugar produces ethanol and carbon dioxide gas.

Question 90.
What happens to the energy produced during cellular respiration?
Answer:
The energy released during cellular respiration is immediately used to synthesise a molecule called ATP. ATP is used to fuel all other activities in the cell. In these activities, ATP breaks down giving a fixed amount of energy. This energy can drive the endothermic reactions taking place in the cell.

Question 91.
Name the energy currency in the living organisms. When and where is it produced?
Answer:
ATP (Adenosine Triphosphate) is the energy currency in the living organisms. It is produced at the end of respiration in mitochondria. The energy released during respiration is used to make an ATP molecule from ADP and inorganic phosphate.

Question 92.
What are the differences between aerobic respiration and anaerobic respiration.
Answer:

Aerobic respiration	Anaerobic respiration
1. Takes place in presence of oxygen.	Takes place in absence of oxygen.
2. Complete oxidation of food takes place.	Incomplete oxidation of food takes place.
3. Large amount of energy is released in the form of ATP (38 ATP).	Small amount of energy is released in the form of ATP (2 ATP).
4. More efficient form of respiration.	Relatively less efficient form of respiration.

Question 93.
Name some organisms that use the anaerobic mode of respiration.
Answer:
Some organisms that use the anaerobic mode of respiration include yeast and bacteria.

Question 94.
What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
Answer:
Aquatic organisms such as fish take oxygen dissolved in water for respiration. Since the solubility of oxygen in water is less, oxygen dissolved in water is very low. On the other hand, terrestrial organisms take oxygen directly from the atmosphere where oxygen is available in plenty.

Question 95.
Explain briefly the exchange of gases that takes place in plants.
Answer:
Green plants carry out aerobic respiration. Aerobic organisms need to ensure that there is sufficient intake of oxygen. Plants exchange gases through stomata, and the large inter-cellular spaces ensure that all cells are in contact with air. Carbon dioxide and oxygen are exchanged by diffusion here.

They can go into cells or away from them and out into the air. The direction of diffusion depends upon the environmental conditions and the requirements of the plant. At night, when there is no photosynthesis, carbon dioxide elimination is the major exchange activity going on.

During the day, carbon dioxide generated during respiration is used up for photosynthesis. Hence there is no release of carbon dioxide during the day. Instead, oxygen produced during photosynthesis is released into the surroundings.

Question 96.
Why is the rate of breathing faster in aquatic organisms?

OR

Why do aquatic animals breathe faster than terrestrial animals?
Answer:
Aquatic organisms such as fish use oxygen dissolved in water for respiration. But, the amount of dissolved oxygen is fairly low compared to the amount of oxygen in the air. Therefore, aquatic organisms will have to breathe more rapidly to get the required oxygen. This is why the rate of breathing in aquatic organisms is much faster than that seen in terrestrial organisms.

Question 97.
Why do fish die when taken out of water?
Answer:
Fish need oxygen for respiration. However, their body apparatus is designed to utilise only the oxygen dissolved in water. Fish cannot utilize the atmospheric oxygen directly for respiration. When they are taken out of water, they die due to lack of oxygen.

Question 98.
What is the organ of respiration in fish? How does it work?
Answer:
The organ of respiration in fish is called gills. Fish takes in water containing dissolved oxygen through the mouth. This water is passed out through the gills. As the water passes through the gills, oxygen present in water gets into the bloodstream of fish through diffusion.

Question 99.
What type of respiration occurs in human beings? Name the chief organ of respiration in humans.
Answer:
Human beings carry out aerobic respiration. This is a type of respiration that involves the use of oxygen. The chief organ of respiration in human beings is called lungs.

Question 100.
Name the major parts of human respiratory system.
Answer:
respiratory system in human beings consists of nose, throat, trachea, bronchi, and lungs.

Question 101.
Draw a neat, labelled diagram of the human respiratory system.
Answer:

Question 102.
What is epiglottis? What is its function?
Answer:
The lid-like elastic structure that folds over the glottis is called epiglottis. While swallowing, the epiglottis closes the opening to the trachea. This prevents food and liquids from entering the larynx and trachea, directing it instead into the oesophagus.

Question 103.
Describe briefly respiration in human beings.

OR

Explain briefly the breathing cycle in the human body.
Answer:
The human respiratory system is made up of many organs, which include nose, nasal cavity, pharynx, larynx, trachea, bronchi and a pair of lungs. The lungs are the main respiratory organs where exchange of gases takes place.

The air containing oxygen enters the body through nose. There are two openings in our nose called nostrils. The nasal cavity moistens and warms up the inhaled air and traps dust particles present in it.

The nasal cavity opens into the pharynx. Pharynx is the common passage for both air and food. It provides passage into the trachea or the windpipe. The trachea is a thin-walled tube, provided with cartilaginous rings, that extends downward and divides into two major bronchi.

One major bronchus enters the right lung and other enters into the left lung. Each bronchus divides into a number of branches and sub-branches called bronchioles. Each bronchiole divides into alveolar ducts, which enter into alveolar sacs. The alveolar sacs are also called alveoli.

The air that enters the trachea will eventually reach the alveoli. A network of blood capillaries surrounds the alveoli. Here exchange of gases takes place. The oxygen present in the alveoli will enter into the blood stream and carbon dioxide present in the blood will enter the alveoli by diffusion.

The oxygen is carried to all living cells of the body by the blood. The carbon dioxide is thrown out of the body in the form of exhaled air.

Question 104.
How does the nasal cavity filter the inhaled air?
Answer:
The nasal cavity is lined with ciliated epithelial cells, which also secrete mucus. The dust particles are stopped by the hairs in the nasal cavity and are entrapped in the mucus secreted by mucus cells. This is how the nasal cavity filters the inhaled air.

Question 105.
What is trachea? State its function in respiration.
Answer:
A large membranous tube reinforced by rings of cartilage, extending from the larynx to the bronchial tubes is called trachea. Trachea helps the passage of air to and from the lungs.

Question 106.
What prevents the trachea from collapsing between breaths?

OR

Why does the air passage not collapse when there is no air in it?

OR

When we breathe out, why does the air passage not collapse?
Answer:
Trachea is a thin-walled soft tube. It is provided with cartilaginous rings. These rings provide mechanical support and prevent the tube from collapsing between breaths.

Question 107.
Rings of cartilage are present in trachea. Give reason.
Answer:
Rings of cartilage are present in trachea to prevent it from collapsing when less air is present in it.

Question 108.
What are alveoli? What is their function?
Answer:
The tiny air sacs, which appear as balloon-like structures, located at the end of bronchioles inside the lungs are known as alveoli.

Alveolus is composed of a very thin membrane and is surrounded by a network of blood capillaries. This is the site for the exchange of gases inside the lungs. The oxygen present in the inhaled air moves into the blood stream and the carbon dioxide present in the blood will move into the alveoli by diffusion.

Question 109.
How are the alveoli designed to maximise the exchange of eases?
Answer:
Alveoli have small sac-like structures resembling balloons. Blood capillaries surround them. Thus a large amount of air is brought in contact with the air in the lungs. Millions of alveoli are present in the lungs. The presence of millions of alveoli in the lungs provides a very large surface area for the exchange of gases. The availability of large surface area maximises the exchange of gases.

Question 110.
What is diaphragm in the human body? What is its role in breathing?
Answer:
A dome-shaped muscular partition separating the thorax from the abdomen is called diaphragm. It plays a major role in breathing. The diaphragm muscles and external intercostal muscles bring about the contraction and expansion of lungs.

The contraction of the diaphragm increases the volume of the thorax and causes the inflation of the lungs. After inhalation, the diaphragm relaxes. The diaphragm rises again to restore pressure and expel the used air from the lungs and back into the environment.

Question 111.
How is the breathing mechanism controlled in our body?
Answer:
The diaphragm and the intercostal muscles control the breathing mechanism of lungs. Diaphragm is a membrane which separates the thoracic chamber from the abdominal cavity. When diaphragm moves down, the lungs expand and air is inhaled. When diaphragm moves up, the lungs contract and air is exhaled.

Question 112.
How are the tunes designed in human beings to maximise the area for exchange of gases?
Answer:
The interior of lungs is provided with many balloon-like tiny structures called alveoli. These provide a surface where exchange of gases can take place. The walls of alveoli show an extensive network of blood vessels. There are millions of alveoli in each lung. These alveoli maximise the area for exchange of
gases.

Question 113.
Lungs always contain a residual volume of air. Give reason.
Answer:
Lungs always contain a residual volume of air so that there is sufficient time to absorb oxygen and release carbon dioxide.

Question 114.
How is oxygen and carbon dioxide transported in human beings?
Answer:
Oxygen and carbon dioxide are transported in our body through the medium of blood. The oxygen present in the inhaled air gets into the blood stream inside the lungs by diffusion. The human blood has red blood cells (RBC), which contain a pigment called haemoglobin. This pigment carries oxygen to various cells of the body.

The oxygen present in blood enters the cells through diffusion. The carbon dioxide produced in the cells gets into the blood stream by diffusion and gets dissolved in the blood plasma. The deoxygenated blood comes back to the lungs. This is the medium of transport of oxygen and carbon dioxide in our body.

Question 115.
How does the exchange of gases occur in the tissues of our body?
Answer:
Oxygen enters into the blood stream through the blood capillaries surrounding the alveoli inside the lungs. This happens by the process of diffusion where oxygen moves from region of higher concentration to region of lower concentration.

The blood contains carbon dioxide in higher proportion. Now the carbon dioxide from the blood present in the blood capillaries diffuses into the alveoli. The oxygen that enters the blood is carried to the various living cells with the help of haemoglobin present in the RBCs.

The cellular respiration requires oxygen and produces carbon dioxide. The oxygen present in the oxygenated blood enters the cells and tissues by diffusion. This oxygen is utilized by the body cells to break down glucose into carbon dioxide and water producing energy.

The carbon dioxide concentration, therefore, is higher inside the cell. The carbon dioxide inside the cells diffuses into the blood stream from where it is carried back to the lungs for oxygenation.

Transportation

Question 116.
What is transport system with reference to an organism? Why is it necessary?
Answer:
The movement of materials through a biological system at the cellular level is known as transport system. The transport can be across cell membranes and epithelial layers. It also can occur within intracellular compartments and extracellular compartments.

Transport system is necessary to ensure the movement and supply of essential materials to the cells in different parts of the body. The waste products produced in the cells are to be transported to the organs from where they can be excreted. Therefore, transport is most essential to ensure the supply of materials and to move the metabolic wastes.

Question 117.
What is blood? Mention the constituents of human blood.
Answer:
The fluid connective tissue in humans and other animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from the same cells is called blood. The major components of human blood are red blood cells, white blood cells, platelets, and plasma.

Question 118.
List the functions of blood in our body.
Answer:
The following are some of the important functions of blood:

1. It supplies oxygen to every living cell of our body and moves carbon dioxide away from the cells to the lungs.
2. It supplies essential nutrients such as amino acid, fatty acid, glucose etc., to the body cells.
3. It transports waste products away from the cells and moves them to the organ of excretion namely kidney.
4. White blood cells give protection against disease-causing germs.
5. It transports hormones.
6. Platelets in the blood help in the clotting of blood.
7. It regulates our body temperature.

Question 117.
What are the components of the transport system in human beines? What are the functions of these components?
Answer:
The main components of the transport system in human beings are the heart, blood and blood vessels:
1. Heart:
Heart pumps oxygenated blood throughout the body. It receives deoxygenated blood from various parts of the body and sends this impure blood to the lungs for oxygenation.

2. Blood:
Being a fluid connective tissue, blood helps in the transport of oxygen, nutrients, carbon dioxide and nitrogenous wastes.

3. Blood vessels:
The blood vessels (arteries, veins and capillaries) carry blood either away from the heart to various organs or from various organs back to the heart.

Question 120.
What is haemoglobin? What is the normal range of haemoglobin present in human blood?
Answer:
A major protein molecule present in the red blood cells and responsible for transport of oxygen within the body is called haemoglobin.
The normal range of haemoglobin present in human is given in the table below:

Age group	Haemoglobin in g/decilitre
1. Adult men	15.5 ± 2.5
2. Adult women	14.0 ± 2.5
3. Children (3 months to 12 years)	11.0 ± 1.5

Question 121.
Why is human blood red?
Answer:
Human blood contains a red coloured pigment called haemoglobin, which forms a part of red blood cells. Red blood cells are largest in number in the human blood. Therefore, blood is red in colour.

Question 122.
What would be the consequences of a deficiency of haemoglobin in our bodies?
Answer:
Haemoglobin is the respiratory pigment that transports oxygen to the body cells for cellular
respiration. Therefore, deficiency of haemoglobin in blood can affect the oxygen-supplying capacity of blood, which leads to deficiency of oxygen in the body cells.

It may lead to death or to heart failure (due to increased functioning of heart to pump more blood),, breathing problems, tiredness and lack of energy. The deficiency of haemoglobin can also lead to a deficiency disease called anaemia.

Question 123.
What is the organ in our body that pumps blood and ensures its circulation?
Answer:
The organ in our body that pumps blood and ensures its circulation is heart.

Question 124.
Kamala went to a doctor complaining of breathlessness and tiredness. The doctor on detailed examination of her blood has diagnosed that her problem is due to the deficiency of a particular component in her blood. What could this component be? What is the remedy the doctor is likely to suggest?
Answer:
Kamala is most likely to be deficient in haemoglobin content in her blood. The deficiency of haemoglobin probably has impeded oxygen transport and hence she is complaining of tiredness and breathlessness due to the short-supply of oxygen.

Kamala must be given iron either in the form of tablets or injection. If the situation is serious, she must be given suitable blood.

Question 125.
How many chambers are there in the human heart? Name them.
Answer:
The human heart has four chambers. They are right atrium, left atrium, right ventricle and left ventricle.

Question 126.
Draw a neat diagram showing sectional view of the human heart and label the parts.

OR

Draw the diagram showing the sectional view of the human heart. Label the following parts:

1. Aorta,
2. Chamber of the heart that receives deoxygenated blood.

Answer:

• Right atrium – The part that receives deoxygenated blood from the body
• Right ventricle – The part that receives blood from right atrium; pumps blood to lungs for oxygenation
• Septum (dividing wall) – The part that prevents oxygenated and deoxygenated blood from mixing; ensures
• efficient supply of oxygen to the body
• Left atrium – The part to which oxygen-rich blood from the lungs comes
• Left ventricle – The part that receives blood from left atrium; pumps out blood to the body.

Question 127.
Which are the two types of circulation that happen in our body?
Answer:
There are two types of circulation that happen in our body. They are

1. Systemic circulation and
2. Pulmonary circulation.

Question 128.
Explain the circulation of blood in our body.
Answer:
Blood must always circulate to sustain life. It carries oxygen from the air we breathe to cells throughout the body. The pumping of the heart drives this blood flow through the arteries, capillaries, and veins.

One set of blood vessels circulates blood through the lungs for gas exchange. The other vessels carry the blood to the rest of the body. The human heart consists of four chambers namely left atrium, right atrium, left ventricle and right ventricle.

Oxygen-rich blood from the lungs comes to the left atrium. The left atrium relaxes while collecting this blood. The left atrium now contracts. The oxygenated blood in the left atrium is pumped into the left ventricle.

When the muscular left ventricle contracts in its turn, the blood is pumped out to the body. Deoxygenated blood is brought back from different parts of the body to the right atrium. The right atrium then contracts pushing the deoxygenated blood into the right ventricle.

The right ventricle then contracts and pumps the blood into the lungs for oxygenation. The valves prevent the flow of blood in the backward direction when atria or ventricles contract.

Question 129.
Why are walls of the ventricles thicker than those of atria?
Answer:
Ventricles have to pump blood into the various organs and hence they have to be stronger. Therefore, the walls of the ventricles are thicker compared to those of atria.

Question 130.
Draw a neat schematic diagram showing the transport and exchange of oxygen and carbon dioxide in our body during circulation of blood.
Answer:

Question 131.
What is the advantage of having four-chambered heart?
Answer:
In four-chambered heart, the left half is completely separated from the right half by septa. It serves two purposes:

1. It ensures complete segregation of oxygenated and deoxygenated blood (i.e., no mixing).
2. It allows a highly efficient supply of oxygenated blood to all parts of the body. This is useful in warm-blooded animals (like mammals and birds) because they constantly require energy to maintain their body temperature.

Question 132.
Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?

OR

In mammals and birds oxygenated blood and deoxygenated blood get separated. Why?
Answer:
Warm-blooded animals such as birds and mammals maintain a constant body temperature by cooling themselves when they are in a hotter environment and by warming their bodies when they are in a cooler environment. Hence, these animals require more oxygen to produce enough energy to maintain their body temperature.

Therefore, it is necessary for these animals to separate oxygenated and deoxygenated blood, so that their circulatory system is more efficient and can maintain constant body temperature.

Question 133.
Describe double circulation in human beinss. Why is it necessary?
Answer:
The heart receives deoxygenated blood from different parts of the body, and it pumps this blood to the lungs. The oxygenated blood from the lungs returns to the heart, which is pumped again into different parts of the body by the heart. Thus, the blood passes twice through the heart making one complete round through the body. This is called double circulation.

Double circulatory system is necessary to ensure that we are giving our tissues and muscles blood full of oxygen, instead of a mixture of oxygenated and deoxygenated blood. This separation of oxygenated and deoxygenated blood ensures highly efficient supply of oxygen to the body. It also helps in maintaining constant body temperature.

Question 134.
What is blood pressure? Mention its types. What is the normal value of pressure in a healthy adult?
Answer:
The force that blood exerts against the wall of a vessel is called blood pressure. There are two types of blood pressure namely

1. Systolic blood pressure and
2. Diastolic blood pressure. The normal systolic pressure in a healthy adult is about 120 mm of Hg and diastolic pressure is 80 mm of Hg.

Question 135.
What is systolic blood pressure and diastolic blood pressure? Name the instrument commonly used to measure blood pressure.
Answer:
The pressure of blood inside the artery during ventricular systole (contraction) is called systolic pressure. The pressure in artery during ventricular diastole (relaxation) is called diastolic pressure. The instrument commonly used to measure blood pressure is called sphygmomanometer.

Question 136.
Name the various types of blood vessels that carry blood in our body.
Answer:
The various blood vessels in our body that carry blood are arteries, veins and capillaries.

Question 137.
What are arteries? Mention their features.
Answer:
Blood vessels that carry blood away from the heart are called arteries. Arteries usually carry oxygenated blood. Arteries have thick and elastic walls.

Question 138.
What are veins? Mention their features.
Answer:
Blood vessels that carry blood towards the heart are called veins. Veins usually carry deoxygenated blood. These vessels are thin walled and have valves all along them to prevent reverse flow of blood.

Question 139.
Why are valves present in heart and veins?
Answer:
Valves are present in heart and veins to ensure that blood does not flow backward, i.e., to allow flow only in one direction.

Question 140.
Why do veins have thin walls as compared to arteries?
Answer:
The wall of the arteries is found to be thicker than that of veins. This is because the blood that is carried by the arteries from the heart to the capillaries will be at high pressure and will flow in pulses.

Therefore, arteries need thicker walls to prevent the arteries from collapsing. The blood flowing through the veins will be at much lower pressure and the flow of blood is smooth. Therefore, veins have thinner walls compared to walls of arteries.

Question 141.
Distinguish between arteries and veins.
Answer:

Arteries	Veins
1. They carry blood away from the heart.	They carry blood towards the heart.
2. They have a thick elastic wall.	They have a thin wall.
3. They usually carry oxygenated blood.	They usually carry deoxygenated blood.
4. They do not have valves.	They have valves to prevent reverse flow of blood.

Question 142.
What is a blood capillary? What is the thickness of their walls?
Answer:
One of the minute blood vessels that connects arteries and veins and is a part of an intricate network throughout the body for the interchange of oxygen, carbon dioxide, and other substances between blood and tissue cells is called a blood capillary. Blood capillaries have very thin walls whose thickness is equal to the thickness of a cell.

Question 143.
What is the function of blood capillaries in our body?
Answer:
Blood capillaries connect arteries and veins. They perform the function of exchange of food materials, gases and metabolic wastes.

Question 144.
What are platelets? What is their function?
Answer:
A small, colourless, disc-shaped cell without a nucleus, found in large numbers in our blood, is called platelet. Platelets are involved in the clotting of blood.

Question 145.
How many platelets are normally found in adult human blood?
Answer:
Adult human blood contains about 2,50,000 platelets per cubic millimetre of blood.

Question 146.
What happens if platelet number falls drastically in our blood?
Answer:
Blood platelets are essential for the clotting of blood. The deficiency of platelets affects the clotting of blood and hence the person may suffer from severe loss of blood in the event of an internal or external injury.

Question 147.
What is lymph? How does lymph protect the body?
Answer:
The nearly colourless watery fluid containing chiefly white blood cells that is collected from the tissues of the body and transported in the lymphatic system is called lymph. Lymph is blood minus red blood cells.

Lymph produces antibodies which help to fight diseases. It contains a type of white blood cells which removes bacteria and foreign bodies from tissues and thus protects the body against diseases.

Question 148.
Distinguish between blood and lymph.
Answer:

Blood	Lymph
1. Red in colour.	Colourless.
2. Blood circulates in a closed circuit of blood vessels.	Lymph circulates through tissue spaces into the vascular system.
3. It is the main transport system of the body.	It is a parallel transport system in the body.
4. Red blood cells are present.	Red blood cells are absent.
5. Blood vascular system consists of blood, heart, arteries and veins.	Lymphatic vascular system consists of lymph, lymph nodes, lymph capillaries and lymph vessels.

Question 149.
Distinguish between plasma and lymph.
Answer:
Blood plasma is the liquid part of blood, always contained in blood vessels. Blood plasma comprises blood cells and plasma proteins.

Lymph is the fluid contained in lymphatic vessels. It is the liquid part of the lymphatic system devoid of plasma proteins.

Question 150.
List the functions of lymph.
Answer:
Lymph produces antibodies which help to fight diseases. Lymph also carries digested and absorbed fat from intestine and drains excess fluid from extracellular space back into the blood.

Question 151.
What are the components of the transport system in highly organised plants?
Answer:
The transport system in highly organized plants consists of two different types of conducting tissues namely the xylem and the phloem.

The xylem tissues conduct water and minerals obtained from soil to the rest of the plant. The phloem tissues transport food materials from the leaves to different parts of the plant body.

Question 152.
What are water-conducting tissues in plants called?
Answer:
Water-conducting tissues in plants are called xylem tissues.

Question 153.
What are food-conducting tissues in plants called?
Answer:
Food-conducting tissues in plants are called phloem tissues.

Question 154.
What is a xylem tissue composed of?
Answer:
Xylem tissue is composed of xylem parenchyma, xylem fibres, xylem vessels and tracheids.

Question 155.
How are water and minerals transported in plants?

OR

Explain the strategy of transportation of water to the highest points of the plant body by the xylem tissue.
Answer:
The vascular tissues called xylem transport water and minerals in plants. Transpiration creates a suction pressure, as a result of which water is forced into the xylem cells of the roots. Then there is a steady movement of water from the root xylem to the rest of the parts of the plant. .

Question 156.
What is phloem tissue? How many types of cells are found in phloem tissues? Name them.
Answer:
A type of vascular tissue in plants involved in the transport of food is known as phloem tissue. There are four types of cells in phloem tissues. They are sieve tubes, companion cells, phloem fibres and phloem parenchyma.

Question 157.
What is translocation?
Answer:
The transport of soluble products of photosynthesis within the plant body is called translocation.

Question 158.
Where does translocation occur in plants?
Answer:
Translocation occurs in the part of the vascular tissue known as phloem.

Question 159.
How is food transported in plants?

OR

Explain the process of translocation of food materials in plants.
Answer:
Specialized vascular tissues called phloem are involved in the transport of food materials from the leaves to the different parts of the plant. The transportation of food in phloem is achieved by utilizing energy from ATP which helps in creating osmotic pressure that transports food from the area of higher concentration towards the area of lower concentration.

Question 160.
What are the differences between the transport of materials in xylem and phloem?
Answer:
Xylem tissues transport water and minerals from the roots to the rest of the parts of the plant body. Phloem tissues transport food from the leaves to all the parts of the plant body.

Question 161.
What are the various materials transported by phloem tissues within a plant body?
Answer:
The phloem tissues transport the products of photosynthesis, amino acids and a few other materials within the body of plants.

Question 162.
How does the translocation of materials happen in phloem tissues?

OR

Explain the process of transportation of substances in phloem.
Answer:
The translocation of food and other substances takes place in the sieve tubes of the phloem tissue with the help of adjacent companion cells both in upward and downward directions. The translocation in phloem is achieved by utilising energy.

Material like sucrose is transferred into phloem tissue using energy from ATP. This increases the osmotic pressure of the tissue causing water to move into it. This pressure moves the material in the phloem to tissues, which have less pressure. This allows the phloem to move materials according to the plant’s needs.

Question 163.
Give an example to show that phloem moves materials inside a plant according to plant’s needs.
Answer:
Phloem moves materials inside a plant according to plant’s needs. For example, in spring, sugar stored in root or stem tissue would be transported to the buds in order to facilitate their growth.

Question 164.
Distinguish between xylem and phloem.
Answer:

Xylem	Phloem
1. These are water-conducting tissues in vascular plants.	These are food-conducting tissues in vascular plants.
2. Has a tubular structure with soft walled ceils.	Has a tubular structure with hard walled cells.
3. The water moves in only one direction.	Food moves in both directions – upward and downward.
4. Xylem moves water and minerals obtained from the soil.	Phloem transports products of photosynthesis from the leaves where they are synthesised to other parts of the plant.

Question 165.
What is transpiration in plants? How is this process helpful to the plant?
Answer:
The loss of excess water in the form of vapour from the aerial parts of the plant is known as transpiration.

Transpiration helps in the absorption and upward movement of water and minerals dissolved in it from roots to the leaves. It also helps in temperature regulation.

Question 166.
Which mechanism plays an important role in transportation of water in plants:

1. During daytime,
2. At night?

Answer:

1. During daytime, transpiration pull plays an important role in transportation of water in plants.
2. At night, root pressure plays an important role in transportation of water in plants.

Question 167.
How does the movement Of water occur through xylem during day time and night time?
Answer:
At the roots, cells in contact with the soil actively take up ions. This creates a difference in the concentration of these ions between the root and the soil. Water, therefore, moves into the root from the soil to eliminate this difference.

This means that there is steady movement of water into root xylem, creating a column of water that is steadily pushed upwards. This effect of root pressure in transport of water is more important at night. During the day, when the stomata are open, the transpiration pull becomes the major driving force in the movement of water in the xylem.

Excretion

Question 168.
Define excretion. What is its importance?
Answer:
The process by which organisms throw out the metabolic wastes from their body is called excretion.

Throwing out of metabolic wastes and other chemicals from the body is important because metabolic processes inside our body produce many substances that are unwanted and toxic. Their build up inside the body can harm vital organs, affect their functioning and may even cause death.

Question 169.
How do unicellular organisms carry out excretion?
Answer:
Most unicellular organisms carry out excretion by the process of diffusion. When the concentration of metabolic wastes within the body increases, it is passed to the surrounding medium by simple diffusion.

Question 170.
What are the various excretory organs in the human body? Which is the chief organ of excretion in human beings?
Answer:
The various excretory organs in our body are skin, lungs and kidneys. The chief organs of excretion in human beings are the kidneys.

Question 171.
Name the organ that excretes carbon dioxide from our body.
Answer:
Carbon dioxide is excreted from our body by the lungs.

Question 172.
What does the major excretory system in human beings consist of?
Answer:
The major excretory system in human beings consists of a pair of kidneys, a pair of ureters, a urinary bladder and a urethra.

Question 173.
Draw a neat, labelled diagram of the excretory system in human beings.
Answer:

Question 174.
What are kidneys? Where are they located in the human body?
Answer:
Either of a pair of bean shaped organs that are located in the rear of the abdominal cavity and involved in the excretion of metabolic wastes from our body is called kidney. Kidneys are located in the abdomen, one on either side of the backbone.

Question 175.
What is the function of kidneys in our body?
Answer:
The primary function of the kidney is to make urine and purify the blood. It removes excess water from the body and nitrogenous wastes from blood in the form of urine.
Kidneys also maintain and control the balance of water and mineral ions in body fluids.

Question 176.
What is the structural and functional unit of the kidney called?
Answer:
The structural and functional unit of the kidney is called nephron.

Question 177.
Name the two major components of normal human urine.
Answer:
Normal human urine consists of 95% water and about 5% nitrogenous wastes mostly in the form of urea and uric acid.

Question 178.
Draw a neat diagram showing the structure of a nephron and label the parts.
Answer:

Question 179.
What is the cup-shaped structure of nephron called?
Answer:
The cup-shaped structure of nephron is called Bowman’s capsule.

Question 180.
What is Bowman’s capsule? What is its function?
Answer:
A cup-shaped structure around the glomerulus of each nephron of the kidney is called Bowman’s capsule. Bowman’s capsule serves as a filter to remove organic wastes, excess inorganic salts, and water.

Question 181.
What is ureter?
Answer:
The duct that carries urine from the kidney to the bladder is called ureter.

Question 182.
What is urinary bladder?
Answer:
A muscular sac in the abdomen, which receives urine from the kidneys and stores it for excretion, is called urinary bladder.

Question 183.
What is urethra?
Answer:
The duct that passes urine out of the body from the bladder is called urethra.

Question 184.
Mention the functions of the following:

1. kidneys,
2. ureters,
3. urinary bladder,
4. urethra,
5. nephrons.

Answer:

1. Kidneys: It removes excess water from the body and nitrogenous wastes from blood in the form of urine.
2. Ureters: These are muscular tubes that transport urine from each kidney to the bladder.
3. Urinary bladder: Urinary bladder is a sac that collects and holds urine that comes from the ureters.
4. Urethra: Urethra is a narrow passageway where urine passes from the bladder to the outside of the body. This is known as urination.
5. Nephrons: These are the filtering units of the kidneys.

Question 185.
Describe the structure and functioning of nephrons.
Answer:
Structure of a nephron: A nephron consists of a Bowman’s capsule in which glomerulus is present (cluster of capillaries). The afferent artery brings the impure blood to nephron. The cup-shaped structure (Bowman’s capsule) forms the tubular part of nephron, which leads to collecting duct.
Functioning of Nephron:
1. Filtration:
The renal artery is a wider tube, which gradually becomes narrow in the glomerulus. Due to difference in the width, pressure difference is caused and water with dissolved impurities is squeezed out from the tube. It is collected in the Bowman’s capsule and passed into the tube.

2. Reabsorption:
The above filtrate passes through the tubule where most of the water, glucose, amino acids are selectively reabsorbed by the capillaries which are surrounding the tubule.

3. Urine formation:
The water and impurities that are not reabsorbed are sent to a collecting duct. This filtrate contains more of dissolved nitrogenous wastes in the form of urea and hence called urine. From here the urine enters the ureter and is collected in the urinary bladder.

Question 186.
Name the factors on which the amount of water reabsorbed along the tubular part of nephron depends.
Answer:
The amount of water reabsorbed by nephron depends on two major factors:

1. The amount of excess water present in the body.
2. The amount of dissolved waste to be excreted out of the body.

Question 187.
Compare the functioning of alveoli in the tunes and nephrons in the kidneys with respect to
their structure and functioning.
Answer:
1. Alveoli:
Structure:

• Alveoli are the structural and functional unit of lungs.
• Alveoli are small, balloon-like structures present inside the lungs.
• The walls of the alveoli are one cell thick and it contains an extensive network of blood capillaries.

Function:

• The function of the alveoli is to get oxygen into the blood stream for transport to the tissues, and to remove carbon dioxide from the blood stream.
• Alveoli are the site of gaseous exchange.

2. Nephrons:
Structure:

• Nephron is the structural and functional unit of kidneys.
• Nephrons are tubular structures present inside the kidneys.
• A nephron is made up of the glomerulus and a long renal tube. The glomerulus is a network of intertwined capillaries. It is enclosed in a cup-shaped structure called ‘ the bowman’s capsule.

Function:

• Nephrons regulate the concentration of water and salts by filtering the blood, reabsorbing what is needed and excreting the wastes as urine.
• Nephrons are the basic filtration unit.

Question 188.
How is the amount of urine produced reeulated?
Answer:
The amount of urine largely depends on the amount of water reabsorbed. The amount of water reabsorbed by the nephron tubule depends on:
1. The amount of water in the body: When water is abundant in the body tissues, large quantity of dilute urine is excreted out. When water is less in quantity in the body tissues, a small quantity of concentrated urine, with less water content, is excreted.

2. The amount of dissolved wastes, especially nitrogenous wastes, like urea and uric acid and salts in the body: When there is more quantity of dissolved wastes in the body, more quantity of water is required to excrete them. So, the amount of urine produced increases. When the amount of these substances in the body is less, then less urine is produced.

3. The amount of urine produced is also regulated by certain factors such as habitat of an organism and certain hormones such as Anti-diuretic hormone (ADH) which control the movement of water into and out of the nephrons.

Question 189.
What are the methods used by plants to set rid of excretory products?
Answer:
The following are some of the methods used by plants to get rid of excretory products:

1. Gaseous wastes such as carbon dioxide are removed through stomata.
2. Excess water is thrown out of the plant body by transpiration.
3. Many plant waste products are stored in cellular vacuoles.
4. Some plants store their waste products in their leaves, which eventually fall off.
5. Some plants store waste products, especially in old xylem, in the form of resins and gums.
6. Plants also excrete some waste substances into the soil around them.

Fill In The Blanks

1. The functional unit of kidneys is called nephron
2. The number of chambers in the human heart is four
3. The chief organ of excretion in humans is kidneys
4. Xylem: Water :: Phloem: Food
5. Blood cells involved in the clotting of blood are known as Platelets
6. The enzyme present in saliva is amylase
7. The enzyme present in gastric juice is pepsin
8. The organ in our body where digestion of food begins is mouth
9. The process of synthesis of food in plants is called photosynthesis
10. The number of chambers in the heart of fish is two
11. The chief purpose of respiration is the production of energy
12. The only vein that carries oxygenated blood in our body is pulmonary vein

Multiple Choice Questions

Question 1.
The life process that converts chemical energy into heat energy is
(A) Nutrition
(B) Respiration
(C) Excretion
(D) Transpiration
Answer:
(B) Respiration

Question 2.
The kidneys in human beings are a part of the system for
(A) nutrition.
(B) respiration.
(C) excretion.
(D) transportation.
Answer:
(C) excretion.

Question 3.
The xylem in plants are responsible for
(A) transport of water
(B) transport of food
(C) transport of amino acids
(D) transport of oxygen
Answer:
(A) transport of water

Question 4.
The food synthesized by plants is stored in the leaves in the form of
(A) glucose
(B) starch
(C) fructose
(D) glycogen
Answer:
(B) starch

Question 5.
The autotrophic mode of nutrition requires
(A) carbon dioxide and water
(B) chlorophyll
(C) sunlight
(D) all of the above.
Answer:
(D) all of the above.

Question 6.
The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
(A) cytoplasm
(B) mitochondria
(C) chloroplast
(D) nucleus.
Answer:
(B) mitochondria

Question 7.
The role of bile during digestion is
(A) emulsification of fat
(B) digestion of fat
(C) absorption of fat
(D) assimilation of fat
Answer:
(A) emulsification of fat

Question 8.
The breakdown of pyruvate that results in the release of carbon dioxide, water and energy occurs in
(A) cytoplasm
(B) mitochondria
(C) chloroplast
(D) nucleus.
Answer:
(B) mitochondria

Question 9.
Choose the event among the following that does not occur in photosynthesis:
(A) Absorption of light energy by chlorophyll
(B) Reduction of carbon dioxide to carbohydrates
(C) Oxidation of carbon to carbon dioxide
(D) Conversion of chemical energy into light energy.
Answer:
(C) Oxidation of carbon to carbon dioxide

Question 10.
The filtration units of kidneys are called
(A) nephrons
(B) neurons
(C) ureter
(D) urethra
Answer:
(A) nephrons

Question 11.
The enzyme that mixes first with food in the digestive tract of human beings is
(A) Pepsin
(B) Cellulase
(C) Amylase
(D) Trypsin
Answer:
(C) Amylase

Question 12.
The correct statement among the following is
(A) Heterotrophs utilise solar energy for photosynthesis.
(B) Heterotrophs do not synthesise their own food.
(C) Heterotrophs synthesise their own food.
(D) Heterotrophs are capable of converting carbon dioxide and water into carbohydrates.
Answer:
(B) Heterotrophs do not synthesise their own food.

Question 13.
The correct sequence of air passage during respiration in humans is:
(A) Nostrils → larynx → pharynx → trachea → lungs
(B) Nasal passage → trachea → pharynx → larynx → alveoli
(C) Larynx → nostrils → pharynx → lungs
(D) Nostrils → pharynx → larynx → trachea → alveoli
Answer:
(D) Nostrils → pharynx → larynx → trachea → alveoli

Question 14.
Which among the following is the correct path of urine flow in our body?
(A) kidney → ureter → urethra → urinary bladder
(B) kidney → urinary bladder → urethra → ureter
(C) kidney → ureter → urinary bladder → urethra
(D) urinary bladder → kidney → ureter → urethra
Answer:
(C) kidney → ureter → urinary bladder → urethra

Question 15.
The opening and closing of the stomatal pore depends upon
(A) concentration of carbon dioxide in stomata
(B) oxygen
(C) temperature
(D) water in guard cells
Answer:
(D) water in guard cells

Question 16.
The internal (cellular) energy reserve in autotrophs is
(A) glycogen
(B) protein
(C) starch
(D) fatty acid
Answer:
(C) starch

Question 17.
The part of the alimentary canal where food is finally digested is
(A) stomach
(B) mouth cavity
(C) large intestine
(D) small intestine
Answer:
(D) small intestine

Question 18.
Which is the correct sequence of parts in the human alimentary canal?
(A) Mouth → oesophagus → stomach → small intestine → large intestine
(B) Mouth → stomach → small intestine → oesophagus → large intestine
(C) Mouth → oesophagus → stomach → large intestine → small intestine
(D) Mouth → stomach → oesophagus → small intestine → large intestine
Answer:
(A) Mouth → oesophagus → stomach → small intestine → large intestine

Question 19.
Most plants absorb nitrogen in the form of
(A) proteins
(B) nitrates and nitrites
(C) urea
(D) elemental nitrogen
Answer:
(B) nitrates and nitrites

Question 20.
The group of organisms that has the longest small intestine is
(A) Autotrophs
(B) Herbivores
(C) Carnivores
(D) Omnivores
Answer:
(B) Herbivores

Question 21.
Bile juice is produced in
(A) Gall bladder
(B) Blood platelets
(C) Liver
(D) Gastric glands in the stomach
Answer:
(C) Liver

Question 22.
The correct pathway of blood in our circulatory system is
(A) atria → ventricles → arteries → veins
(B) ventricles → atria → veins → arteries
(C) ventricles → veins → arteries → atria
(D) veins→ ventricles → atria → arteries
Answer:
(A) atria → ventricles → arteries → veins

Question 23.
In the human digestive system, the organs that secrete enzymes pepsin and trypsin are respectively
(A) Pancreas and liver
(B) Stomach and pancreas
(C) Stomach and salivary gland
(D) Pancreas and gall bladder
Answer:
(B) Stomach and pancreas

Question 24.
The enzyme amylase present in the saliva
(A) converts glucose to starch
(B) converts proteins to amino acids
(C) converts starch to maltose
(D) converts starch to protein
Answer:
(C) converts starch to maltose

Question 25.
The metal associated with haemoglobin is
(A) mercury
(B) silver
(C) copper
(D) iron
Answer:
(D) iron

Match The Following

Question 1.

Column A	Column B
1. Phloem	a. Helps in clotting of blood
2. Nephron	b. Site for aerobic respiration
3. Mitochondria	C. Transports oxygen in our body
4. Platelets	d. Digestion gets completed here
5. Small intestine	e. Food-conducting tissues in plants
	f. Functional unit of kidneys

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