Living Science 2020 2021 Solutions for Class 8 Science Chapter 9 Reproduction are provided here with simple step-by-step explanations. These solutions for Reproduction are extremely popular among class 8 students for Science Reproduction Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Living Science 2020 2021 Book of class 8 Science Chapter 9 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Living Science 2020 2021 Solutions. All Living Science 2020 2021 Solutions for class 8 Science are prepared by experts and are 100% accurate.
Page No 121:
Question 1:
Suppose a disease affecting the reproductive system, strikes all individuals of a species. What will happen to the species? Give reasons.
Answer:
In case a disease affecting the reproductive system strikes every individual of a species, the species will become extinct. This is because such type of disease will affect the ability of organisms to produce young ones. The overall result will be that any member of the species will not be able to give birth to young ones and thus, species will become extinct.
Page No 121:
Question 2:
In what kind of animals does fertilization normally occur outside the body? Where does it occur in the case of humans?
Answer:
The fertilization process which occurs outside the body of an organism is called external fertilization. This type of fertilization is found in aquatic animals such as jellyfish and starfish. In case of humans, fertilization occurs inside the body of females and is termed as internal fertilization.
Page No 121:
Question 3:
In humans, which organ produces the egg, and which organ produces the sperms? How many of each are produced at a time?
Answer:
The egg is produced by ovaries in humans, whereas sperms are produced by testes in humans. Testes generally produce approximately millions of sperms and ovaries produce a single egg in a month.
Page No 121:
Question 4:
During the reproduction process in humans, after which process does a new individual start getting formed?
Answer:
In humans, fertilization results in the formation of a zygote. This zygote later develops into a complete organism. The formation of zygote marks the formation of a new individual. Thus, after fertilization, a new individual starts getting formed.
Page No 121:
Question 5:
Which two processes are responsible for the development of embryo in multicellular organisms?
Answer:
The development of embryo in multicellular organisms is regulated by two processes namely cell division and cell differentiation. Cell division helps in the growth of the organism and cell differentiation allows cell to specialize to perform specific functions.
Page No 123:
Question 1:
In animals where fertilization is internal, development of an individual after fertilization can occur in two different ways. What are these two ways?
Answer:
Animals that show internal fertilization can develop through viviparous or oviparous processes. Oviparous animals lay eggs which develop into young ones. Viviparous animals, on the other hand, give birth to young ones. Examples of oviparous and viviparous organisms are snakes and dogs, respectively.
Page No 123:
Question 2:
In what way is the process of development of an adult from an egg different in birds and frogs?
Answer:
The difference in development of an adult from an egg in frogs and birds is as follows:
| Development of frogs | Development of birds |
| 1. A free living larva stage is observed in case of frogs. | 1. Larva stage is not found during the development of birds. |
| 2. The larva undergoes metamorphosis to develop into adult frog. | 2. Metamorphosis is not observed during the development of birds. |
Page No 123:
Question 3:
Describe the process by which Amoeba reproduces.
Answer:
An Amoeba reproduces by the process of binary fission. In this process, the nucleus firstly divides to form two equal parts. This is followed by the division of cytoplasm. The cytoplasm also divides equally into two parts and each part receives a nucleus. This results in the formation of two daughter Amoebae which grow and eventually split to form mature Amoeba.
Page No 123:
Question 4:
Hydra develops a bulb-like projection that finally changes into a new individual. What is the projection called?
Answer:
Hydra shows asexual reproduction by the process of budding. In this process, a bulb-like projection which is termed as a bud appears that further develops into a complete organism.
Page No 125:
Question 1:
Which of these are the male reproductive organs in humans?
(a) sperms
(b) ova
(c) testes
(d) ovaries
Answer:
(c) testes
Testes are male reproductive organs in humans. They produce male gametes known as sperms.
Page No 125:
Question 2:
Which of the following is a hermaphrodite animal?
(a) frog
(b) cow
(c) dog
(d) earthworm
Answer:
(d) earthworm
In earthworm, single individual has both male and female reproductive organs. Thus, it is known as hermaphrodite animal.
Page No 125:
Question 3:
In __________, the offspring grows out of the parent's body.
(a) Hydra
(b) Amoeba
(c) Paramecium
(d) human
Answer:
(a) Hydra
Hydra reproduces asexually through budding. Budding involves the formation of new individual from the bulging of parent's body.
Page No 125:
Question 4:
In humans, fertilization occurs in
(a) oviduct.
(b) uterus.
(c) ovary.
(d) vagina.
Answer:
(a) oviduct
In humans, fertilisation occurs in oviduct. It is also known as fallopian tube.
Page No 125:
Question 5:
In a mosquito, the eggs hatch to produce
(a) pupa.
(b) larva.
(c) embryo.
(d) adult mosquito.
Answer:
(b) larva
The mosquito's life cycle includes egg, larva, pupa and adult stages. Once the egg hatches, it develops through larval stage and progress to pupal stage and, finally, emerges as an adult.
Page No 125:
Question 6:
Which of the following reproduces by splitting into two?
(a) Hydra
(b) mosquito
(c) Amoeba
(d) frog
Answer:
(c) Amoeba
Amoeba reproduces by splitting into two. This type of asexual reproduction in which animal reproduces by dividing into two individuals is known as binary fission.
Page No 126:
Question 7:
The fusion of sperm and egg produces
(a) zygote.
(b) larva.
(c) pupa.
(d) embryo.
Answer:
(a) zygote
The fusion of sperm (male gamete) and egg (female gamete) produces a single cell called zygote.
Page No 126:
Question 8:
Humans start becoming sexually mature at the ages of
(a) 10−16.
(b) 3−5.
(c) 13−18.
(d) 25−30.
Answer:
(a) 10-16
Humans start to sexually mature at the ages of 10-16.
Page No 126:
Question 1:
Improper working of the reproductive organs can lead to death. True or false?
Answer:
False, improper working of the reproductive organs cannot lead to death as these organs are not essential for an organism to stay alive. However, the impairment of reproductive organs can lead to severe consequences and the organism will not be able to produce offspring in the future.
Page No 126:
Question 2:
What is the process of fusion of sperm and ovum called?
Answer:
The process of fusion of sperm and ovum is called fertilisation.
Page No 126:
Question 3:
The fusion product of sperm and ovum is known as __________
Answer:
The fusion product of sperm and ovum is known as zygote.
Page No 126:
Question 4:
Organisms in which male and female gametes are present in the same organism are called __________
Answer:
Organisms in which male and female gametes are present in the same organism are called hermaphrodite.
Page No 126:
Question 5:
An earthworm, being a hermaphrodite, can reproduce on its own without the need of a partner. True or false?
Answer:
False.
Although earthworm is hermaphrodite and bears both male and female reproductive organs, it cannot fertilise on its own and requires a partner for the purpose.
Page No 126:
Question 6:
In frogs, is the fertilization external or internal?
Answer:
In frogs, the fertilisation is external because it takes place outside the female body.
Page No 126:
Question 7:
What is the onset of sexual maturity in animals known as?
Answer:
The onset of sexual maturity in animals is known as puberty.
Page No 126:
Question 8:
In humans, which organ produces the ovum?
Answer:
In humans, an ovary produces the ovum.
Page No 126:
Question 9:
Fertilization in humans takes place in the uterus. True or false?
Answer:
False.
Fertilisation in humans takes place in oviduct or fallopian tube. The fertilised egg then moves and attaches itself to the wall of uterus.
Page No 126:
Question 10:
Females of all mammals produce a single ovum at a time. True or false?
Answer:
False.
In human female, an ovary releases a single ovum every month. Number of ova released by females varies from species to species.
Page No 126:
Question 11:
In mosquito, the life cycle is as follows: egg → pupa → larva → mosquito. True or false?
Answer:
False.
The mosquito's life cycle is as follows:
egg → larva → pupa → adult mosquito
Page No 126:
Question 12:
The process of cells changing their size, shape and form to form specialized cells is called __________
Answer:
The process of cells changing their size, shape and form to form specialised cell is called differentiation.
Page No 126:
Question 13:
Is binary fission sexual or asexual?
Answer:
Binary fission is a type of asexual reproduction in which an animal reproduces by dividing into two.
Page No 126:
Question 14:
The transformation of the larva into an adult through drastic changes is called __________
Answer:
The transformation of the larva into an adult through drastic changes is called metamorphosis.
Page No 126:
Question 1:
Why is reproduction important?
Answer:
Reproduction is important for living organisms to maintain their population and to ensure the continuance of their own kind, generation after generation. Without reproduction, the life would not exist.
Page No 126:
Question 2:
How is sexual reproduction different from asexual reproduction?
Answer:
Difference between sexual and asexual reproduction:
| Sexual Reproduction | Asexual Reproduction |
| It is the process that involves two parents (i.e. a male and a female). | It is the process that requires only one parent. |
| The offspring produced are not identical to their parent. | The offspring produced are identical to their parent. |
| It gives rise to diversity among living organisms. | It does not gives rise to diversity among living organisms. |
Page No 126:
Question 3:
What is menstruation?
Answer:
Menstruation is the process in which blood and mucus flow out every month through the vagina due to the rupture of the lining of uterus if fertilisation does not occur.
Page No 126:
Question 4:
What is cell division?
Answer:
Cell division is a process of cell multiplication where a parent cell divides into two or more new daughter cells.
Page No 126:
Question 5:
What is metamorphosis?
Answer:
Metamorphosis is a biological process of transforming larva into an adult. The process involves relatively abrupt changes in the animal's structure through cell growth and development.
Page No 126:
Question 6:
List the various stages in the life cycle of a mosquito.
Answer:
The various stages in the life cycle of a mosquito are as follows:
Egg → larva → pupa → adult mosquito
Page No 126:
Question 1:
Differentiate between external and internal fertilization, giving two examples of each.
Answer:
Difference between external and internal fertilisation
| External Fertilisation | Internal Fertilisation |
| Fertilisation that takes place outside the female body is called external fertilisation. | Fertilisation that takes place inside the female body is called internal fertilisation. |
| Large number of eggs are produced. | Less number of eggs or a single egg is produced. |
| Examples include fish, frog, starfish, etc. | Examples include humans, cows, hens, etc. |
Page No 126:
Question 2:
How does fertilization occur in frogs?
Answer:
In frog, fertilisation takes place outside the female body. This type of fertilisation is known as external fertilisation.
During rainy season, the female frog lays hundreds of eggs in water. As the eggs are laid by females, the male frog releases sperms close to it. These sperms swim in water, reach the eggs and fertilise them.
Page No 126:
Question 3:
How and where does fertilisation take place in human beings?
Answer:
Fertilisation is the process in which the sperm (male gametes) fuses with the ovum (female gametes) to form a single cell called zygote. During sexual intercourse, sperm cells enter the women's vagina, swim through the uterus (womb) and enter the oviduct, where a ripe egg may be present. When they reach a potential egg, one of the sperms fuses with the egg to form a zygote. The zygote undergoes division and specific changes to grow into a new individual.
Page No 126:
Question 4:
What happens in the female body if the ovum is not fertilized by a sperm?
Answer:
If fertilisation does not takes place in the female body, the inner lining of uterus breaks down slowly and is released out in the form of blood and mucus from the vagina. This process is known as menstruation. This is usually a 28-day cycle.
Page No 126:
Question 5:
How does Hydra reproduce?
Answer:
Hydra reproduces asexually through budding.
In Hydra, the cells divide rapidly at a specific site and develop as an outgrowth called bud. These buds remain attached to the parent body and develop into smaller individuals. When these individuals become fully mature, they detach from the parent body and develop as an independent individual.
Page No 127:
Question 6:
Explain the difference between viviparous and oviparous animals.
Answer:
Difference between viviparous and oviparous animals
| Viviparous Animals | Oviparous Animals |
| Animals that give birth to young ones are known as viviparous animals. | Animals that lay eggs outside their body are known as oviparous animals. |
| The development of embryos takes place within the mother's body from where the embryo gains nourishment. | The development of embryo does not takes place within the mother's body. |
| Example includes humans, certain fishes, etc. | Example includes frogs, chickens, butterfly, etc. |
Page No 127:
Question 7:
Explain what happens after a hen lays a fertilised egg.
Answer:
After a hen lays a fertilised egg, the parent hen sits and warms the egg or keeps it safely in a warm place till it hatches. After three weeks of development, the chick is completely developed and bursts out opening the egg shell.
Page No 127:
Question 1:
Give details of two different ways in which a zygote develops in animals with internal fertilisation.
Answer:
The following are the two different ways in which a zygote develops in animals with internal fertilisation:
(i) Fertilisation in reptiles, birds and mammals, including humans, takes place inside the female's body. Millions of sperm cells from the male are transferred to the female body. When they reach the egg, one of the sperm fuses with it to form a fertilised egg known as zygote.
(ii) Hermaphroditic animals like earthworm cannot fertilise on their own. They needs to mate with another worm in order to exchange genetic material. Here, the eggs are fertilised internally with the sperms received from the partner.
Page No 127:
Question 2:
What is puberty? What is it caused by? What changes occur in boys and girls during puberty?
Answer:
Puberty is the time of life when a boy or a girl becomes sexually mature. It happens at the age group of 10–15 for girls and 11–16 for boys.
Puberty is caused by the release of hormones.
Changes that occur in boys during puberty:
(i) Deepening of voice
(ii) Growth of facial hair (beard and moustaches)
(iii) Development of muscles and broadening of shoulders
(iv) Production of sperms by the testes
Changes that occur in girls during puberty:
(i) Development of breast
(ii) Widening of pelvic region and broadening of hips
(iii) Start of menstrual cycle
Page No 127:
Question 3:
Discuss how a zygote develops into an individual in humans.
Answer:
After the process of fertilisation, the zygote travels down in the oviduct and divides repeatedly to give rise to a ball of cells. The cells then begin to form groups that develop into different tissues and organs of the body. This developing structure is called embryo. The embryo gets embedded in the wall of uterus for further development. The stage of embryo in which our body parts can be distinguished easily is known as a foetus. The embryo/foetus grows in the mother's uterus for about nine month. After nine months, the mother is ready to give birth to a fully developed foetus.
Page No 127:
Question 4:
Explain the life cycle of a frog with the help of a labelled diagram.
Answer:
The life cycle of a frog has three distinct stages:
Eggs → Tadpole (larva) → Adult frog
Female frogs lay eggs. These eggs hatch into larvae known as tadpoles. The tadpoles are fish-like and have gills, a tail and a small circular mouth. They can swim freely within the water. After few weeks, tadpoles grow and undergo some abrupt changes in their structure through cell growth and development. As a result of such changes, the tadpoles are gradually transformed into frogs.
Page No 127:
Question 1:
Can the process of a child changing into an adult be called metamorphosis?
Answer:
No. The process of metamorphosis involves relatively abrupt changes in the animal's body. Since, in human beings, body parts similar to the adult are present from the time of the birth, there are no drastic changes. Hence, the process of a child changing into an adult cannot be called metamorphosis.
Page No 127:
Question 2:
Frogs and fish lay hundreds of eggs at a time. However, their population is very little compared to the number of eggs they lay. Why?
Answer:
It is because some of the eggs and sperms may be exposed to water movement, wind and rainfall and may get destroyed. Also, sometimes, these factors may prevent the sperms from reaching the eggs. Thus, production of a large number of eggs and sperms is necessary (as in the case of frogs and fish) to ensure fertilisation of at least a few of them.
Page No 127:
Question 3:
Why do you think it is necessary for frogs and fishes to lay so many eggs?
Answer:
Yes, it is necessary for frogs and fishes to lay large number of eggs because they are exposed to the external environment that may destroy many eggs. Hence, laying eggs in a large number promote fertilisation and also increase the chances of survival of at least few of the fertilised eggs.
Page No 127:
Question 4:
What do you think would have happened if humans also gave birth to a large number of babies at the same time?
Answer:
If humans gave birth to a large number of babies at the same time, then our earth would have overpopulated and our natural resources would have depleted.
Page No 127:
Question 5:
Can a woman with a blocked fallopian tube give birth to a child? Why?
Answer:
No. A woman with a blocked fallopian tube cannot give birth to a child. It is because fertilisation takes place in the woman's fallopian tube. If the fallopian tube is blocked, the egg released from the ovary would not be able to pass through the blockage. As a result, the egg and sperm won't be able to meet and fertilisation would not take place.
Page No 127:
Question 6:
Under what circumstances can twins be born in humans?
Answer:
Under following circumstances twins can be born in humans:
(i) The zygote or fertilised egg is a single cell. Sometimes, a single fertilised egg or zygote splits into two, each half developing into an embryo. This results in identical twins.
(ii) Sometimes, two eggs (instead of one egg) are released from the ovary. This may result into fraternal twins, whereby two eggs are fertilised by two sperms. As a result, two zygotes are formed, which separately develops into two embryos. Fraternal twins are also known as non-identical twins because they are genetically different and may not be of same sex.
Page No 127:
Question 7:
Why is it that dogs always produce several puppies, whereas human beings usually produce only one child at a time?
Answer:
Dogs are poly-ovulatory species. In these species, more than one ovum is released from the ovary at the time of ovulation. Therefore, they always produce several puppies. However, in humans, a single ovum is released from the ovary every month. Thus, they usually produce only one child at a time.
Page No 127:
Question 1:
Kamlesh thinks that to produce test tubes babies, an egg and a sperm are placed in a test tube and then allowed to fuse under controlled conditions. The baby then develops in the test tube.
Is Kamlesh correct? Which part of his thinking is incorrect?
Answer:
Kamlesh was correct in thinking that to produce test tubes babies, an egg and a sperm are placed in a test tube and then allowed to fuse under controlled conditions. But he was wrong in thinking that the baby develops in the test tube.
After the egg and sperm are allowed to fuse under controlled conditions, an embryo is formed. This embryo is then inserted into the women's womb where it gets implanted. It develops into a baby within 9 months and is finally delivered out from the body.
Page No 127:
Question 1:
Mr Sinha is 65 years old. He was sitting on the seat meant for senior citizens in the metro train. He saw a pregnant lady standing. He immediately got up and offered his seat to the lady. Why did Mr Sinha do this even though the seat was meant for senior citizens?
Answer:
Mr. Sinha behaved as a responsible citizen. He understood the fact that the pregnant women needed the seat more than him as it would have been uncomfortable for her to stand for a long duration.
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