Class 8 Science

CBSE Class 8 Science Chapter 5 Conservation of Plants And Animals Important Questions With Answers Long Answer Questions

Question 1. Is deforestation associated with global warming? Explain.
Answer: Trees (and other plants) use carbon dioxide gas from the atmosphere for the process of food making called photosynthesis. When a lot of trees are cut down during deforestation, then lesser number of trees will be left. The lesser number of trees will use up less carbon dioxide, due to which the amount of carbon dioxide in the atmosphere will still increase. In this way. Deforestation increases the level of carbon dioxide in the atmosphere. Carbon dioxide gas traps the sun’s heat rays reflected by the Earth (causing the greenhouse effect). Trapping of heat rays by carbon dioxide increases the temperature of Earth’s atmosphere. This will lead to global warming. The gradual increase in the overall temperature of Earth’s atmosphere due tothe greenhouse effect caused by the increased level of carbon dioxide in the atmosphere is called global warming.

Question 2. How does deforestation lead to frequent floods and droughts?
Answer: When the forest trees are cut down, the number of trees decreases, which results in less transpiration. Reduced transpiration causes a decrease in the amount of water vapour in the atmosphere, resulting in less rainfall.

When there is less rainfall in an area, then less water percolates into the ground. Due to this, the groundwater level also gets lowered. The shortage of surface water (in ponds, lakes, etc.) and groundwater due to persistent low rainfall in an area can lead to droughts.

Deforestation also leads to a decrease in the water-holding capacity of the soil. The movement of water from the soil surface into the ground is reduced. So, there are floods.

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Question 3. Which of these are the effects of deforestation? Circle ‘Yes’ or ‘No’ for the correct response.

Answer: Yes, No, Yes

CBSE Class 8 Science Chapter 5 Conservation Of Plants Very Short Answer Questions

Question 1. Arrange the following to show how deforestation leads to water pollution.

1. The roots of the trees no longer have a firm grip on the soil.
2. Rain falls onto the ground.
3. The trees of a forest are cut down.
4. The loose soil gets washed away into a nearby body of water.

Answer: 3-1-2-4

Question 2. A gas is utilised by the trees and plants in photosynthesis. The same gas also traps the heat rays reflected by the Earth, and is also given out by humans during respiration. Name the gas and the phenomenon of an increase in temperature for which it is responsible.
Answer: The gas is carbon dioxide, and the phenomenon is global warming.

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Question 3. Why is it important to conserve forests?
Answer: Forest conservation maintains the balance in nature. It acts as a carbon sinks absorbing CO 2 and keeps global warming at bay.

Question 4. Mention any one action that you have undertaken to conserve trees.
Answer: I have planted some trees a nd look after them carefully so that they are well protected. This is the action I have taken to conserve trees.

Question 5. ‘Variety of all forms of life found in a region’ is known by a specific name; what is it?
Answer: Biodiversity.

Question 6. Name the protected area built to support biodiversity.
Answer: A Biosphere reserve supports biodiversity.

Question 7. Out of the three biosphere reserves, a National park or a wildlife sanctuary, which is the largest?
Answer: Biosphere reserve is the largest of the three, and it may contain a National park or a wildlife sanctuary.

Question 8. Endemic fauna is restricted to a particular area. Name a few in India.
Answer: Bison and flying squirrel are endemic fauna of Pachmarhi Biosphere Reserve in India.

Question 9. What is the unique feature of the biodiversity found in the Pachmarhi Biosphere Reserve?
Answer: The biodiversity found in Pachmarhi Biosphere Reserve is similar to that of the upper Himalayan peaks and to those belonging to the Western Ghats.

Question 10. How are even small animals important in an ecosystem?
Answer: Small animals might be small in size, but their role in the ecosystem cannot be ignored. They are important in an ecosystem as they form part of food chains and food webs.

Question 11. A group of cats is found in a forest that interbreed freely. What is the term used for them?
Answer: A species is a group of the same kind of organisms that can interbreed to produce fertile offspring.

Question 12. Name the plant found in Satpura forests.
Answer: The finest Indian teak is found in the Satpura forests.

Question 13. Name the first reserve forest of India.
Answer: Satpura National Park is the first reserve forest of India.

Question 14. Mention the aim of the Forest (Conservation) Act.
Answer: The aim of the Forest (Conservation) Act is the preservation and conservation of natural forests and meeting the basic needs of the people living in or near the forests.

CBSE Class 8 Science Chapter 5 Conservation Of Plants Short Answer Questions

Question 1. We have often read in the newspaper about the careful use of natural resources. What is the term used for it? Mention some of the Earth’s natural resources that need to be used carefully.
Answer: ‘Conservation’ is a term used to describe the prudent (careful and sensible) use of natural resources. The Earth’s natural resources that need to be conserved are air, water, soil, minerals, fuels, plants, and animals.

Question 2. Soil erosion and desertification are the consequences of deforestation. Justify.
Answer: Deforestation causes soil erosion, i.e., removal of the top layer ofsoil. It also changes the physical properties of soil. Thus, exposing the lower, hard, and rocky layers of soil that have less humus and are less fertile. Gradually, the fertile land gets converted into deserts. This is called desertification.

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Question 3. A new species X is introduced into a forest. How is it likely to affect the local species of that area?
Answer: The new species is likely to affect the local species as it poses threats in the following manner

1. Preying on native species.
2. Out-competing for food or other resources.
3. Causing or carrying a disease.
4. Preventing native species from reproducing.
5. Changing food webs.

Question 4. Sometimes, animals enter human habitation, killing people and causing damage to materials. Why do the animals behave like this?

Answer: Animal behaviour can be understood from the explanation given below

As human populations expand into wild animal habitats, their territory is displaced. Reduction in the availability of food sources forces the animal to seek alternate sources. Thus, drawing them towards human habitation.

Question 5. Roshni attended a seminar on forest and Wildlife conservation. She, on returning home, discussed it with her brother. If she had given some measures, she would have mentioned conserving forests and wildlife.

Answer: Forests and wildlife can be conserved by following

Protection by law. It is very necessary to have strict laws and their enforcement for the protection and preservation of wildlife, for Example, hunting regulations.

Reforestation is the act of planting more trees to replace the ones that are cut.

Habitat preservation. In this method, protected areas such as Wildlife sanctuaries, National parks, Biosphere reserves, etc., are established. These areas are large enough to protect the diverse and whole set of ecosystems

Question 6. Why are endemic organisms in greater danger of becoming extinct?
Answer: Endemic organisms are confined to a limited geographical area. They cannot adapt to or live outside their natural habitat; any disturbance to their habitat will adversely affect them. Thus, they are in greater danger of becoming extinct.

Question 7. Why are wildlife sanctuaries important for the conservation of plants and animals?
Answer: In a wildlife sanctuary, killing and capturing wild animals are strictly prohibited. It does not allow any human activity that disturbs the wild animals or their habitat. So, in these areas, animals live in a natural environment, protected from people. This is why sanctuaries are important.

Question 8. Recycling and the saving of paper are related to deforestation. Justify.
Answer: Trees are used in making paper. About 17 fully grown trees are used to make one tonne of paper. So, the wastage of paper is also a cause of deforestation. Therefore, we should recycle and save paper. If we save paper, we can save many trees in a year. In this way, recycling and the saving of paper are directly related to deforestation.

Question 9. Boojho wonders if there is a record of the endangered species.
Answer: The Red Data Book is the source book that keeps a record of all endangered animals and plants.

Question 10. Paheli is curious to know what would happen if we had no wood? Is there any alternative available for wood? Boojho says that paper is one of the important products we get from forests. Boojho asks whether there are any alternatives available for paper
Answer: Without wood, we would not have access to fuel and many other household necessities like paper, matchsticks, furniture, etc. The use of digital technology could replace paper.

CBSE Class 8 Science Chapter 5 Conservation Of Plants Fill In The Blanks

Question 1. A place where animals are protected in their natural habitat is called a _____.
Answer: Wildlife sanctuary

Question 2. Species found only in a particular area are known as ________.
Answer: endemic species

Question 3. Migratory birds fly to faraway places because of __________ changes.
Answer: climatic

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Question 4. __________ traps the heat of the Sun’s rays.
Answer: Carbon dioxide

Question 5. Conversion of fertile land into a desert is called __________
Answer: Desertification

Question 6. Pachmarhi is an example of __________.
Answer: Biosphere reserve

Question 7. Plants found in a particular area are termed as __________.
Answer: flora

Question 8. A group of populations that are capable of interbreeding is called a __________.
Answer: Species

Question 9._________ is an example of the endemic flora of the Pachmarhi Biosphere Reserve.
Answer: Salt

Question 10. _________ is the first reserve forest of India.
Answer: Satpura National Park

Class 8 Science Chapter 5 Conservation Of Plants True or False

Question 1. Green plants utilise oxygen to prepare food through photosynthesis.
Answer: False

Question 2. Endemic species are those that are exclusively found in a particular area.
Answer: True

Class 8 Science Chapter 5 Conservation Of Plants Match The Columns

Question 1. Match Column 1 with Column 2

Answer: A- 4, B-3, C-5, 0-2, H- 1

Question 10. Match Column 1 with Column 2

Answer: A-3, B-1 C-4, D-2

Class 8 Science Chapter 5 Conservation Of Plants

The following question consists of two statements: Assertion (A) and Reason (R). Answer these questions by selecting the appropriate options given below.

1. Both A and R are true, and R is the correct explanation of A
2. Both A and R are true, but R is not the correct explanation of A
3. A is true, but R is false
4. A is false, but R is true

Question 1.

Assertion (A) Deforestation leads to drought.
Reason (R) The consequent increase in temperature on the Earth disturbs the water cycle. This leads to a decrease in rainfall.

Answer: 1. Both A and R are true, and R is the correct explanation of A.

Question 2.

Assertion (A): Conserving biodiversity is a necessity.
Reason (R): Biodiversity is a part of the web of life, and its loss can affect other species and ecosystems.

Answer: 1. Both A and R are true, and R is the correct explanation of A.

Question 3.

Assertion (A): Bison is an example of endemic fauna.
Reason (R): Endemic species are those species that no longer exist anywhere on Earth.

Answer: 3. A is true, but R is false. R can be corrected as the endemic species are those species of plants and animals that are found exclusively in a particular area. For example, bison is an endemic fauna of the Pachmarhi biosphere reserve.

Question 4.

Assertion (A): Members of a species have common characteristics.
Reason (R): Species is a group of populations that are not capable of interbreeding.

Answer: 3. A is true, but R is false. R can be corrected as a Species is a group of populations that are capable of interbreeding.

Question 5.

Assertion (A) Project Tiger was launched by the government of the United States.
Reason (R) It was launched to ensure the survival and maintenance of the tiger population in the country.

Answer: 4. A is false, but R is true. R can be corrected as ‘Project Tiger’ was launched by the government of India.

The following questions consist of two statements: Assertion (A) and Reason (R). Answer these questions by selecting the appropriate option given below.

1. Both A and R are true, and R is the correct explanation of A.
2. Both A and R are true, but R is not the correct explanation of A.
3. A is true, but R is false.
4. A is false, but R is true.

Question 11.

Assertion (A): Wildlife sanctuary, National park, and Biosphere reserve are protected areas.
Reason (R): In these areas, plantation cultivation, grazing, felling trees, hunting, and poaching are prohibited.

Answer: 1. Both A and R are true, and R is the correct explanation of A.

Question 12.

1. Assertion (A): Rock shelters are found inside the Satpura National Park.
2. Reason (R) A total of 55 rock shelters have been identified in the Pachmarhi Biosphere Reserve.

Answer: 2. Both A and R are true, but R is not the correct explanation of A.

CBSE Class 8 Science Chapter 6 Reproduction In Animals Multiple Choice Questions

Question 1. Which of the following is not a part of the human male reproductive system?

1. Testes
2. Oviducts
3. Seminal vesicles
4. Epididymis

Answer: 2. Oviducts

Question 2. Sets of reproductive terms are given below. Choose the set that has an Incorrect combination

1. Sperm, testis, sperm duct, penis
2. Menstruation, egg, oviduct, uterus
3. Sperm, oviduct, egg, uterus
4. Ovulation, egg, oviduct, uterus

Answer: 3. Sperm, oviduct, egg, uterus

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Question 3. Which of the following statements about reproduction in humans is correct?

1. Fertilisation takes place externally
2. Fertilisation takes place in the testes
3. During fertilisation, the egg moves towards the sperm
4. Fertilisation takes place in the human female

Answer: 4. Fertilisation takes place in the human female

Question 4. A stage of sexual reproduction is represented below. Select the correct statement describing the process shown in the image

1. Several ova penetrate the egg cell and fertilise it to form a zygote
2. Several sperm penetrate the egg cell and fertilise it to form a zygote
3. A single ova penetrates the egg cell and fertilises it to form a zygote
4. A single sperm penetrates the egg cell and fertilises it to form a zygote

Answer: 4. A single sperm penetrates the egg cell and fertilises it to form a zygote

Question 5. After fertilisation, the resulting cell, which gives rise to a new individual, is the

1. Embryo
2. Ovum
3. Foetus
4. Zygote

Answer: 4. Zygote

Question 6. Which of these animals reproduces by external fertilisation?

1. Snake
2. Frog
3. Horse
4. Elephant

Answer: 2. Frog

Question 7. Internal fertilisation occurs

1. Inside the male body
2. Outside the male body
3. Inside the female body
4. Outside the female body

Answer: 3. Inside the female body

Question 8. Where doos tho fertilisation of oggs occur In the process of In Vitro Fertilisation (IVF)?

1. Ovary
2. Wate
3. Uterus
4. Petri dish

Answer: 4. Petri dish

Question 9. In human beings, the correct sequence of events

1. Gamete formation, fertilisation, zygote formation embryo
2. Embryo, zygote formation, fertilisation, gamete formation
3. Fertilisation, gamete formation, embryo, zygote formation
4. Gamete formation, fertilisation, embryo, zygote formation

Answer: 1. gamete formation, fertilisation, zygote formation, embryo

Question 10. Animals exhibiting external fertilisation produce a large number of gametes. Pick the appropriate reason

1. The animals are small in size and want to produce more offspring
2. Food is available in plenty of water
3. To ensure a better chance of fertilisation
4. Water promotes the production of a large number of gametes

Answer: 3. To ensure a better chance of fertilisation

Question 11. In human beings, after fertilisation, the structure which gets embedded in the wall of the uterus is

1. Ovum
2. Embryo
3. Foetus
4. Zygote

Answer: 2. Embryo

Question 12. In humans, the development of a fertilised egg takes place in the

1. Ovary
2. Testis
3. Oviduct
4. Uterus

Answer: 4. Uterus

Question 13. Which table given below correctly represents the classification of the animals into viviparous and oviparous animals?

CBSE Difference Between Sexual And Sexual Reproduction Class 8 Notes Long Answer Questions

Question 1. After observing the figure below, answer the following.

Read the following statements and label them in the figure.

1. The part that produces female gametes.
Answer: Ovary (produces gametes)

2. The tire part where the development of the baby takes place.
Answer: Uterus (development of body takes place

3. The part through which the developing embryo passes to reach the uterus.
Answer: Oviduct (Fallopian tube through which the embryo reaches the uterus)

Questions 2. Explain the future development of the embryo that would take place after it gets embedded in the uterus.
Answer: The embryo continues to develop after it gets embedded into the uterus. It divides and differentiates into three germ layers, which give rise to different body parts such as hands, legs, head, eyes, ears, etc.

His stage where all the body parts are distinct and easily identified in a developing embryo is called the foetus. After the completion of the development of the foetus, the mother gives birth to the baby.

Question 3. Consider the diagram below and answer the following question.

1. A mature egg and a sperm unite to form a zygote. In which part of the female reproductive system does a zygote form?

1. 1
2. 2
3. 3
4. 4

Answer: 1. 1

2. How many ova are usually released each month by the ovary of a woman?

1. One
2. Two
3. Fourteen
4. Twenty-four

Answer: 1. One

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3. In which part of the female reproductive system does an embryo implant?

1. 1
2. 2
3. 3
4. 4

Answer: 2. 2

Question 4. Which of these statements is true about a foetus? Circle ‘Yes’ or No for the correct response

Answer:

1. Yes
2. No
3. No

Question 5. The table shows the processes of external fertilisation and internal fertilisation

Which of these is true about external fertilisation and internal Fertilisation?

Answer: Both parents are necessary.

Question 6. The picture shows the life cycle of a moth. What can be concluded from the picture? Circle ‘Yes’ or ‘No’ for the correct response.

Answer:

1. Yes
2. Yes
3. No

Question 7. The pictures show three types of reproduction in animals

Which of those statements is true?

• Type 1 reproduction is called binary fission
• Type 2 reproduction produces two non-identical offspring.
• Type 3 reproduction involves unequal distribution of genetic materials.
• Types 1, 2, and 3 reproduction methods involve a single parent only.

Answer: 2. Type 1, 2, and 3 reproduction methods involve a single parent only.

The following questions consist of two statements:

Assertion (A) and Reason (R). Answer these questions by selecting the appropriate option given below.

1. Both A and R are true, and R is the correct explanation of A
2. Both A and R are true, but R is not the correct explanation of A
3. A is true, but R is false
4. A is false, but R is true

Answer: 10. A-3, B-l.C-4, D-2

Question 8.

Assertion (A) During metamorphosis tadpole is transformed into a caterpillar.
Reason (R) Metamorphosis is a process in which a larva is transformed into an adult

Answer: 1. Both A and R are true, and R is the correct explanation of A

Question 9.

Assertion (A) Cloning of an animal was successfully performed for the first time by Ian Wilmut and his colleagues.
Reason (R) Cloning is the production of a different copy of a cell or any living part or a complete organism

Answer: 3. A is true, but R is false

CBSE Class 8 Science Chapter 6 Reproduction In Animals Short Answer Questions

Question 1. Describe the two modes of reproduction.
Answer: Two modes of reproduction are

Asexual reproduction. It does not involve the fusion of gametes, it results from the multiplication of body cells from a single parent. Daughter cells are identical to the parent. No fertilisation takes place.

Sexual reproduction is characterised by the union of male and female gametes coming from two parents. offspring differ from the parents genetically. Fertilisation takes place

Question 2. It is not necessary to produce a large number of eggs and spores by the animals that reproduce by external fertilisation. Why?
Answer: It is necessary to produce a large number of eggs and sperm by he animals that reproduce by external fertilisation to enhance the chances of fertilisation. As the gametes are released in water, many of them may he carried away by the movement of water, wind, etc., or may be eaten by other aquatic animals, so a large number is released to compensate for the loss.

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Question 3. Mother gives birth to a baby, but the baby has characteristics of both parents. How is this possible?
Answer: Although a mother gives birth to a baby, the baby is formed from the fertilisation of male and female gametes involving two parents. The nuclei of both the parent gametes fuse to form a zygote, thus passing their characteristics to the offspring. This zygote develops inside the female body (uterus) and finally takes birth as a baby

Question 4. Although two cells called gametes fuse, the product formed is a single cell called a zygote. Justify.
Answer: During fertilisation, only the nucleus of the sperm enters the egg cell to form a single-celled structure, which is called a zygote.

Question 5. Can a woman with a blocked Fallopian tube give birth to a baby? How?
Answer: A woman with a blocked Fallopian tube cannot produce babies in the normal way because the eggs released by their ovary cannot meet the sperm and get fertilised in the oviducts. But such women can have babies by using the ‘in vitro fertilisation’ technique.

Question 6. The test-tube babies are called so as they grow inside a test tube. Give your opinion.
Answer: The babies born through the IVF technique are called test-tube babies because the fertilisation takes place in a glass test tube. This is, however, a misleading name as a very brief period is spent in a test tube. After which, the entire growth and development of the baby takes place inside the uterus of the woman as in normal pregnancy.

Question 7. Observe the figure given and answer the questions that follow

Question 8. What happens during the process, and what is formed?
Answer: During the process, the sperm nucleus fuses with the egg nucleus to nun a zygote.

Question 9. The term metamorphosis is not used while describing human development. Why?
Answer: The term ‘metamorphosis’ Is not used while describing human development because in human beings, body parts of an adult arc present from the time of birth llsclf, i.e., while beginning of life as a baby and until you arc an adult, the basic plan of body does not change, On the contrary, in metamorphosis, the parts of the adult arc different from those at the time of birth,.

Question 10. What does the figure represent?

Answer: The figure represents the process of binary fission in Amoeba. During fission, a single Amoeba divides (both nucleus and cytoplasm) to form two daughter cells that develop into two independent Amoeba.

CBSE Class 8 Science Activity: To Observe Budding In Yeast Using Microscope Activities

Aim: To observe the frog eggs

Procedure

1. Visit some ponds or slow-flowing streams during the spring or rainy season.
2. Try to find out clusters of frog eggs floating in water.
3. Note the colour and size of the eggs.

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Observation: We will observe that the colour of the eggs is transparent when unfertilised. If fertilised, a tiny black tadpole appears in the middle. Eggs measure about 2-3mm in size

Simple Experiment To Demonstrate Binary Fission With Playdough Amoeba Activity 2

Aim: To collect the eggs of different oviparous animals. Procedure

1. Collect the eggs of as many oviparous animals as possible (e.g. frog, lizard, butterfly, bird, etc).
2. Make drawings of the eggs that you have collected.

Observation: We will observe that the eggs of different oviparous animals are of different colours and sizes.

Conclusion: From this activity, it is concluded that it is easy to collect the egg of oviparous animals because they lay them outside their bodies.

Egg Fertilization Demonstration Using Balloons And Yarn For Class 8 Activity 3

Aim: To study budding in Hydra with the help of permanent slides.

Materials Required: Permanent slide of Hydra, microscope. Procedure

• Get permanent slides of Hydra and observe them using a microscope.
• Look out carefully for any bulges from the parent body.
• Count the number of bulges that you see in different slides.
• Draw the diagram of Hydra as you see it

Observation: We will observe a small single outgrowth or protuberance on the parent body. This bud develops into a tiny individual, which, when fully mature, detaches from the parent body.

Conclusion: From this activity, we can conclude that Hydra reproduces through budding

Male Reproductive System Parts And Functions Class 8 Explanation Fill In The Blanks

Question 1. Sperms are produced in
Answer: Testes

Question 2. ……Reproduces by budding.
Answer: Hydra

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Question 3. Amoeba is a celled organism…….It reproduces by reproduction. The process of reproduction begins by the devision of The process of reproduction begians by the division of its into two. This is followed by the division of it into two. This type of reproduction is called fission.
Answer: Single, asexual, nucleus, cytoplasm, binary.

Question 4. Reproduction by binary fission occurs in
Answer: Amoeba

Question 5………..reproduces by fragmentation
Answer: Spirogyra

Metamorphosis In Frogs Stages With Diagram Class 8 True Or False

Question 1. All living animals reproduce to produce new young ones.
Answer: True

Question 2. The human egg has a head, middle piece, and tail.
Answer: False, human sperm has a head, middle piece, and tail.

Question 3. Sperms are produced by the ovaries.
Answer: False, sperms are produced by the testes.

Question 4. The male gametes are called sperm.
Answer: False, male gametes are called sperm

Question 5. In adult human females, a single mature egg is released into an oviduct every month
Answer: True

Question 6. Oviparous animals give birth to young ones.
Answer: False, oviparous animals (female) lay eggs

Question 7. Each sperm is a single cell.
Answer: True

Question 8. External fertilisation takes place in a frog.
Answer: True

Question 9.  A new human individual develops from a cell called a gamete.
Answer: False, a new human individual develops from a cell called a zygote

Question 10. An egg laid after fertilisation is made up of a single cell.
Answer: True

Question 11. Amoeba reproduces by budding.
Answer: false, Amoeba reproduces by binary fission

Question 12. Fertilisation is necessary even in asexual reproduction.
Answer: False, fertilisation does not take place in asexual reproduction as no gametes are formed and only a single parent is involved

Question 13. Binary fission is a method of asexual reproduction.
Answer: True

Question 14. A zygote is formed as a result of fertilisation.
Answer: True

Question 15. An embryo is made up of a single cell.
Answer: False, because an embryo is a developing structure formed from a group of dividing cells of a zygote

Question 16. Cows and dogs are viviparous animals.
Answer: True

Question 17. Budding is a method of asexual reproduction.
Answer: True

DIY Model of Frog Life Cycle for Class 8 Project: Match The Columns

Question 1. Match Column 1 with Column 2

Answer: A-3, B-4, C-5, D-1, E-2

Question 10. Match Column 1 with Column 2.

Answer: A-3,B-1,C-4,D-2

NCERT Class 8 Science Chapter 6 – Higher Order Thinking Questions (HOTs) on Animal Reproduction

The following questions consist of two statements: Assertion (A) and Reason (R). Answer these questions by selecting the appropriate option given below

1. Both A and R are true, and R is the correct explanation of A
2. Both A and R are true, but R is not the correct explanation of A
3. A is true, but R is false
4. A is false, but R is true

Question 1.

Assertion (A) The animals that undergo external fertilisation lay hundreds of eggs.
Reason (R): To enhance the chances of fertilisation.

Answer: 2. Both A and R are true, and R is the correct explanation of A.

Question 2.

Assertion (A) Internal fertilisation occurs in many animals, including humans, cows, dogs, and hens.
Reason (R) Fertilisation, which takes place inside the female body, is called internal fertilisation.

Answer: 2. Both A and R are true, and R is not the correct explanation ofA.

Question 3.

Assertion (A) It is easy to collect the eggs of viviparous animals.
Reason (R) They lay eggs outside their body.

Answer: 4. A is false, but R is true. A can be corrected as it is easy to collect the eggs of oviparous animals

Question 4.

Assertion (A) Human beings do not undergo metamorphosis.
Reason (R) The body parts in adults are not similar to those of babies.

Answer: 3. A is true, but R is false. R can be corrected as the body parts in adults are similar to those of babies

Question 5.

Assertion (A) Binary fission and budding are two methods of asexual reproduction
Reason (R) Only a single parent is involved

Answer: 1. Both A and R are true. R is the correct explanation of A

CBSE Class 8 Science Chapter 2 Microorganisms: Friend And Foe Ncert Folder Intext Questions

Question 1. Pahell saw that her mother added a little curd to warm milk to set curd for the next day. She wonders why?
Answer: Curd contains several microorganisms, including the bacterium Lactobacillus, which promotes the formation of curd. It gets multiplied in the milk and converts it into curd

Question 2. Why are children or infants given vaccinations?
Answer: When vaccines are introduced into a healthy child’s (or person’s) body, the body fights and kills the invading bacteria by producing suitable antibodies. These antibodies remain in the body, and the child is protected from disease-causing microbes.

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Question 3. How do you prevent the spread of communicable diseases?
Answer: We can prevent the spread of communicable diseases by taking some precautions, Examplekeeping a handkerchief on the nose and mouth while sneezing and keeping a distance from infected persons.

Question 4. Why does the teacher keep telling the students not to let water collect anywhere in the neighbourhood?
Answer: We should not let water collect anywhere in the neighbourhood because all mosquitoes breed in the water and spread diseases like malaria.

Question 5. Paheli wonders how food can become a ‘poison’?
Answer: Microorganisms that grow on our food sometimes produce toxic substances, which make the food poisonous, causing serious illness and even death.

Question 6. Why does the milk that comes in packets not spoil? What is pasteurisation?
Answer: The milk that comes in packets does not spoil because it is pasteurised milk. It can be consumed without boiling as it is free from harmful microbes. Pasteurisation is a process in which milk is heated to about 70°C for 15-30 seconds and then suddenly chilled and stored. This prevents the growth of microbes. This process was discovered by Louis Pasteur.

Question 7. Can microorganisms be seen with the naked eye? If not, how can they be seen?
Answer: Microorganisms or microbes are too small to be seen by the naked eye. They can be seen with the help of a magnifying glass or microscope.

Question 8. What are the major groups of microorganisms?
Answer: Microorganisms are divided into four major groups, which are as follows

1. Bacteria are single-celled organisms having a rigid cell wall like plant cells. Diseases like typhoid and tuberculosis (TB) are caused by bacteria.
2. Fungi are non-green organisms that obtain their food from dead organic matter.
3. Protozoa are unicellular animals that cause diseases like malaria and dysentery.
4. Algae are a photoautotrophic organism that may be unicellular or multicellular.

Question 9. Name the microorganisms that can fix atmosphorlc nitrogen in the soil.
Answer: Bacteria such as Rhizobium and certain blue-green algae (Anabaena, Nosloe) present in the soil can fix atmospheric nitrogen and convert it into usable nitrogenous compounds.

Question 10. Write 10 lines on the usefulness of microorganisms in our lives.
Answer: Microorganisms are useful to humans and plants in the following ways

• They are used in the preparation of food items such as pieces of bread.
• Bacteria are used in the conversion of milk into curd.
• They are used for the large-scale production of alcohol, wine, and acetic acid.
• Several medicines, such as antibiotics, are being productÿ by bacteria and fungi.
• They are used to check microbial infections in animals.
• Vaccines are made by dead or weakened microbes.
• Some bacteria and blue-green algae increase the soil fertility by fixing atmospheric nitrogen.
• They decompose the dead organic wastes of plants and animals.
• They are used in the cleaning up of the environment.
• Certain microbes are also used in the biological treatment of sewage and industrial effluents.

Question 11. Write a short paragraph on the harmful effects of microorganisms.
Answer: Microorganisms are harmful to human beings in many ways. They cause diseases in humans, plants and animals. For example, in humans, bacteria cause diseases such as cholera, typhoid, tuberculosis, etc.

In cattle, the foot and mouth disease is caused by a virus. Also, several microbes cause diseases in plants, for  Example, Citrus canker disease, and late blight of potato. Some microbes grow on food and secrete toxic substances which make the food poisonous.

Class 8 Science Chapter 2 Fill In The Blanks

Question 1. Microorganisms can be seen with the help of a __________.
Answer: Microscope

Question 2. Blue-green algae fix ________directly from the air and enhance the fertility of soil.
Answer: Nitrogen

Question 3. Alcohol is produced with the help of _________.
Answer: Yeast

Question 4. Cholera is caused by ________.
Answer: Bacteria

Question 5. All microorganisms are classified into major ______ groups.
Answer: Four

Question 6. Paramecium is a slipper-shaped _____.
Answer: Protozoan

Question 7. Alexander Fleming discovered mould _______.
Answer: Penicillin

Question 8. Pathogens are ________ causing organisms.
Answer: Disease

Question 9. ______ could be due to the consumption of food spoiled by some microorganisms
Answer: Food Poisoning

Question 10. The process in which sugar is converted into alcohol is called __________.
Answer: Fermentation

Question 11. _________is a process of heating the milk at high temperature, then cooling it suddenly and storing it.
Answer: Pasteurisation

Question 12. ___________ is the vector of the dengue virus
Answer: Aedes

Class 8 Science Chapter 2 True Or False

Question 1. Microorganisms can be seen with the naked eye.
Answer: False, microorganisms are very small and cannot be seen by nthe aked eye. They can be seen with the help of a microscope.

Question 2. Microorganisms can be found only in air and water.
Answer: False, microorganisms are found everywhere in the air, water, inside our body, etc.

Question 3. Viruses can only multiply in a living cell.
Answer: True

Question 4. All microbes are disease-causing.
Answer: False, some microbes are useful, for example, Lactobacillus.

Question 5. Microorganisms are also used in the cleaning up of the environment.
Answer: True

Question 9. Jams, jellies and squashes are preserved by adding salt.
Answer: False

Question 10. The atmospheric nitrogen cannot be utilised by the living organisms.
Answer: True

Question 11. Viruses can be seen by simple microscopes.
Answer: False

CBSE Class 8 Science Chapter 2 Match The Columns

Question 1. Match the microorganisms given in Column 1 to the group to which they belong in Column 2.

Answer: A-4, B-3, C-1, D-2

Question 2. Match the Items given In Column 1 with those of Column 2

Answer: A-4, B-5, C-1, D-2, E-3

Question 3. Match the names of scientists given in Column 1 with the discovery made by them given in Column 2.

Answer: A-3, B-2, C-4, D-1

Question 4. Match the organisms in Column A with their action in Column B.

Answer: A-(5), B-(1), C-(2), D-(3), E-(4), F-(5)

Question 5. Match Column I with Column II.

Answer: A-6, B-5.C-7, D-4, E-3, F-2.G-1

Class 8 Science Chapter 2 Microorganisms: Friend And Foe

The following questions consist of two statements: Assertion (A) and Reason (R). Answer these questions by selecting the appropriate option given below

1. Both A and R are true, and R is the correct explanation of A
2. Both A and R are true, but R is not the correct explanation of A.
3. A is true, but R is false
4. A is false, but R is true.

Question 1.

• Assertion (A) Lactobacillus converts curd into milk.
• Reason (R) The conversion of milk into curd is known as fermentation.

Answer: 4. A is false, but R is true. A can be corrected as Lactobacillus converts milk into curd.

Question 2.

• Assertion (A) Streptomycin and tetracycline are examples of antibiotics.
• Reason (R) Antibiotics help in the growth of disease-causing microorganisms.

Answer: 3. A is true, but R is false. R can be corrected as Antibiotics are the medicines that kill or stop the growth of disease-causing microorganisms.

Question 3.

1. Assertion (A) Sodium benzoate and sodium metabisulfite are common preservatives.
2. Reason (R) They are used to control the growth of microbes.

Answer: 1. Both A and R are true, and R is the correct explanation of A.

Question 4.

1. Assertion (A) Pasteurised milk cannot be consumed without boiling.
2. Reason (R) Pasteurised milk is free from microorganisms.

Answer: 4. A is false, but R is true. A can be corrected as Pasteurised milk can be consumed without boiling.

Question 5.

1. Assertion (A) Rhizobium is an example of a nitrogen-fixing bacterium.
2. Reason (R) This bacterium converts nitrogen compounds into nitrogen gas.

Answer: 3. A is true, but R is false. R can be corrected as Rhizobium bacteria convert nitrogen gas into nitrogenous compounds, which are utilised by plants.

The following questions consist of two statements: Assertion (A) and Reason (R); Answer these questions by selecting the appropriate option given below.

1. Both A and R are true, and R is the correct explanation of A.
2. Both A and R are true, but R is not the correct explanation of A.
3. A is true, but R is false.
4. A is false, but R is true

Question 1.

1. Assertion (A) Antibiotics are effective against cold and flu
2. Reason (R) Cold and flu are caused by a virus.

Answer: 4. A is false, but R is true

Question 2.

1. Assertion (A): Decomposers clean the environment.
2. Reason (R) They decompose the harmful dead and decaying remains of plants and animals.

Answer: 1. Both A and R are true, and R is the correct explanation of A.