Science Ncert Exemplar 2019 Solutions for Class 8 Science Chapter 9 Reproduction In Animals are provided here with simple step-by-step explanations. These solutions for Reproduction In Animals are extremely popular among class 8 students for Science Reproduction In Animals Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Science Ncert Exemplar 2019 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 Science Ncert Exemplar 2019 Solutions. All Science Ncert Exemplar 2019 Solutions for class 8 Science are prepared by experts and are 100% accurate.
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Question 1:
Sets of reproductive terms are given below. Choose the set that has an incorrect combination.
(a) sperm, testis, sperm duct, penis
(b) menstruation, egg, oviduct, uterus
(c) sperm, oviduct, egg, uterus
(d) ovulation, egg, oviduct, uterus
Answer:
Sperm is a male gamete produced by the testes. The oviduct or fallopian tube is present in the female reproductive organ. Egg or ova is a female gamete produced by ovaries and uterus is a female reproductive organ where the development of baby takes place.
Hence, the correct answer is option (c).
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Question 2:
In humans, the development of fertilized egg takes place in the
(a) ovary
(b) testis
(c) oviduct
(d) uterus
Answer:
The development of fertilized eggs takes place in the uterus of human females. After fertilization, the fertilized egg is implanted in the uterus where its further development takes place.
Hence, the correct answer is option (d).
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Question 3:
In the list of animals given below, hen is the odd one out.
human being, cow, dog, hen
The reason for this is
(a) it undergoes internal fertilisation.
(b) it is oviparous.
(c) it is viviparous.
(d) it undergoes external fertilisation.
Answer:
Hen is oviparous. It lay eggs and the young ones are hatched from eggs. Other animals like cows, dogs, and human beings are viviparous. They directly gave birth to a young one.
Hence, the correct answer is option (b).
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Question 4:
Animals exhibiting external fertilisation produce a large number of gametes. Pick the appropriate reason from the following.
(a) The animals are small in size and want to produce more offsprings.
(b) Food is available in plenty in water.
(c) To ensure better chance of fertilisation.
(d) Water promotes production of large number of gametes.
Answer:
A large number of gametes are produced during external fertilization to ensure better chances of fertilisation. In external fertilisation, the fusion of male and female gamete takes place outside the female body. Males release sperm in water so there is a chance of getting sperm washed off by water or other external factors.
Hence, the correct answer is option (c).
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Question 5:
Reproduction by budding takes place in
(a) Hydra
(b) Amoeba
(c) Paramecium
(d) bacteria
Answer:
In Hydra, asexual reproduction takes place by budding. An outgrowth develops on a parent's body and detaches when becomes mature. In this way, a new individual develops from the bud and this process is called budding.
Hence, the correct answer is (a).
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Question 6:
Which of the following statements about reproduction in humans is correct?
(a) Fertilisation takes place externally.
(b) Fertilisation takes place in the testes.
(c) During fertilisation egg moves towards the sperm.
(d) Fertilisation takes place in the human female.
Answer:
In humans, the process of fertilisation takes place in the human female. This process involves the fusion of sperm (male gamete) with egg (female gamete) in the oviduct of the female to form a zygote.
Hence, the correct answer is option (d).
Page No 48:
Question 7:
In human beings, after fertilisation, the structure which gets embedded in the wall of uterus is
(a) ovum
(b) embryo
(c) foetus
(d) zygote
Answer:
The process of fertilisation involves the fusion of sperm and egg in the oviduct of the female to form a zygote. Zygote further divides and gives rise to a ball of cells. This developing structure is called an embryo which is embedded in the wall of the uterus.
Hence, the correct answer is option (c).
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Question 8:
Aquatic animals in which fertilisation occurs in water are said to be:
(a) viviparous without fertilisation.
(b) oviparous with external fertilisation.
(c) viviparous with internal fertilisation.
(d) oviparous with internal fertilisation.
Answer:
Aquatic animals are oviparous as eggs are laid by the females and males release sperms which swim randomly with water with help of its long tail. In this way, the egg is fused with the sperm outside the body of the female and fertilisation takes place. This type of fertilisation is termed external fertilisation. It is common in aquatic animals like fish, starfish and so on.
Hence, the correct answer is option (b).
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Question 9:
After fertilisation, the resulting cell which gives rise to a new individual is the
(a) embryo
(b) ovum
(c) foetus
(d) zygote
Answer:
A zygote is formed as a result of the fusion of male and female gamete. A zygote further develops into an embryo as it divides repeatedly to give rise to a ball of cells which is called an embryo. Embryo gets embedded in the uterus and further develops into a foetus.
Hence, the correct answer is option (d).
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Question 10:
In human beings, the correct sequence of events during reproduction is
(a) gamete formation, fertilisation, zygote, embryo
(b) embryo, zygote, fertilisation, gamete formation
(c) fertilisation, gamete formation, embryo, zygote
(d) gamete formation, fertilisation, embryo, zygote
Answer:
The correct sequence of events during reproduction involves:
Gamete formation- The male and female gametes are produced by testes and ovaries respectively.
Fertilisation- The process of fusion of male and female gamete in the oviduct of the female.
Zygote- The process of fertilisation results in the formation of a zygote.
Embryo- The zygote is further divided into a structure called an embryo and is embedded in the wall of the uterus for further development.
Hence, the correct answer is option (a).
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Question 11:
Although 2 cells called gametes fuse, the product formed is a single cell called zygote. Justify.
Answer:
During the process of fertilisation, the nucleus of the sperm fuses with the nucleus of the egg and forms a zygote. Other parts of the sperm degenerate. Thus giving rise to a single cellular zygote.
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Question 12:
Stages in the lifecycle of silkworm are given below. Write them in sequential order.
pupa, silkworm, egg, silkmoth
Answer:
The stages in the lifecycle of silkworm involve:
.
Female moths lay eggs and on hatching, the silkworm is produced. The caterpillar or the pupa of silkworm looks different from the adult moth. This process of transformation of a larva into an adult through drastic changes is called metamorphosis.
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Question 13:
What is the importance of reproduction?
Answer:
Reproduction is a biological process that involves the production of offspring. It ensures the continuation of species from one generation to other generation.
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Question 14:
In markets, eggs of birds are available but never eggs of dogs. Why?
Answer:
Birds are oviparous whereas dogs are viviparous. Viviparous animals directly give birth to young ones and oviparous animals lay eggs. Birds lay eggs while in dogs, the mother gives birth to young ones. Thus, the eggs of dogs are not available in the market.
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Question 15:
The eggs of frogs do not have shells for protection, yet they are safe in water. How?
Answer:
The frog's egg is delicate as it is not covered by a shell. It is covered by a layer of a jelly-like substance that holds the eggs together and provides protection to the egg from external factors.
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Question 16:
Fill up the blanks with the terms given below:
body, asexual, binary, single, nucleus
Amoeba is a ___________ celled organism. It reproduces by___________ reproduction. The process of reproduction begins by the division of its ___________ into two. This is followed by the division of its ___________ into two. This type of reproduction is called ___________ fission.
Answer:
Amoeba is a ____single_______ celled organism. It reproduces by_____asexual______ reproduction. The process of reproduction begins by the division of its ______nucleus_____ into two. This is followed by the division of its ______body_____ into two. This type of reproduction is called _____binary______ fission.
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Question 17:
The term metamorphosis is not used while describing human development. Why?
Answer:
The metamorphosis involves the process of transformation of the larva into an adult through a drastic change. Human development involves the process of gamete formation in which male and female gametes are formed. Then the process of fertilisation involves the fusion of male and female gamete to form a zygote which is further developed into an embryo and embedded in the uterus for further development. Even after birth, the human baby grows gradually to become an adult and there is no morphological difference between them. Hence, the term metamorphosis is not used while describing human development.
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Question 18:
Mother gives birth to a baby but the baby has characters of both parents. How is this possible?
Answer:
Sexual reproduction involves the fusion of both male and female gametes. So, the baby receives characters from both parents. Only the process of fertilization and implantation takes place in the mother's body.
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Question 19:
How is reproduction in Hydra different from that in Amoeba?
Answer:
Asexual reproduction takes place in both Hydra and Amoeba. Hydra reproduces by budding in which a bud developed on the parent body as an outgrowth. On maturation, these buds developed as an individual and detaches from the parent body. Amoeba reproduces by binary fission in which the parent body divides into two daughter cells. In this, the division of the nucleus takes place into two.
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Question 20:
State whether the following statements are True or False. If false, correct the statement:
(a) External fertilisation can occur both in water and on land.
(b) The eggs of fish are covered by hard shells for protection.
(c) Human egg has a head, middle piece and tail.
(d) In adult human females, a single mature egg is released into an oviduct every month.
Answer:
(a) False. External fertilisation can only occur in water and is common in aquatic animals.
(b) False. The eggs of fishes are covered by a jelly-like substance that provides protection.
(c) False. Human sperms have a head, middle piece and tail.
(d) True. A single matured egg is released by the ovary every month in the oviduct for fertilisation by sperm.
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Question 21:
Why do only male gametes have a tail?
Answer:
Sperm is produced in the male reproductive system. For successful fertilization, the sperms have to reach the ovum which is non-motile in nature. Tails present in male gametes help in the movement of sperm towards the egg to complete the process of fertilization in the oviduct of the female.
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Question 22:
What does in the given figure represent?
Answer:
The given figure represents the process of binary fission in Amoeba. It is a type of asexual reproduction in which the parent cell divides into two daughter cells. At first, the nucleus divides into two and finally, two individuals are produced.
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Question 23:
Observe the figure given and answer the questions that follow.
(a) Label A and B.
(b) Identify the process.
(c) What happens during this process and what is formed?
Answer:
(a) A-Sperm, B-Egg.
(b) The above process represents the process of fertilisation in which fusion of male gamete and female gamete takes place.
(c) In fertilisation, the nucleus of sperm fuses with the nucleus of the egg results in the formation of a zygote.
Page No 50:
Question 24:
How can we say that fish exhibits external fertilisation?
Answer:
External fertilisation is common in aquatic animals such as fish and starfish. The female fish lays eggs in the water and the male fish releases sperms. The fusion of egg and sperm takes place outside the body. Thus, we can say that fish exhibits external fertilisation.
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Question 25:
After observing the given figure answer the following.
a. Read the following statements and label them in the figure:
(i) The part which produces female gametes.
(ii) The part where development of the baby takes place.
(iii) The part through which the developing embryo passes to reach the uterus.
b. Explain the future development of the embryo that would take place after it gets embedded in the uterus.
Answer:
a.
b. The embryo is embedded in the uterine wall for further development. It continues to develop into the uterus and gradually develops the body parts hands, legs, eyes, head, nose, heart, etc. The stage in which all the body parts are identified is called the foetus. The mother gives birth to the baby when the development of the foetus is completed after nine months.
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Question 26:
Hens and frogs are both oviparous exhibiting different types of fertilisation. Explain.
Answer:
Both hens and frogs are oviparous as they lay eggs. In hens, internal fertilisation takes place in which fusion of male gamete and female gamete occurs inside the body of the female. But the development of the chick from the embryo takes place outside the body of the female. In frogs, external fertilisation takes place in which fusion of male gamete and female gamete occurs outside the body of the female in the water. All the events of fertilisation, from the formation of the zygote to the embryo and young ones, are developed outside the body in water.
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Question 27:
Observe the following figures.
(a) (b) (c) (d)
(i) Identify the stages a to d in the given figures during development of human baby.
(ii) Arrange the stages in correct sequence of development.
(iii) Explain the development that takes place in any one stage.
Answer:
(i) (a) The embryo is embedded in the wall of the uterus for further development.
(b) The process of fertilisation takes place that involves the fusion of male and female gametes.
(c) The process of fertilisation results in the formation of a zygote and its further development into an embryo.
(d) Fusion of nuclei of the male and female gamete.
(ii) (b) The process of fertilisation takes place that involves the fusion of male and female gametes in the oviduct.
(d) Fusion of nuclei of the male and female gamete.
(c) The process of fertilisation results in the formation of a zygote and its further development into an embryo.
(a) The embryo is embedded in the wall of the uterus for further development.
(b) (d) (c) (a)
(iii) During the process of fertilisation, the nuclei of sperm and egg are fused together to form a single nucleus results in the formation of zygote.
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