reproduction-in-animalsWHERE cd.courseId=12 AND cd.subId=16 AND chapterSlug='reproduction-in-animals' and status=1SELECT ex_no,page_number,question,question_no,id,chapter,solution FROM question_mgmt as q WHERE courseId='12' AND subId='16' AND chapterId='372' AND ex_no!=0 AND status=1 ORDER BY ex_no,CAST(question_no AS UNSIGNED) CBSE Class 8 Free NCERT Book Solution for Science

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Chapter 9 : Reproduction in Animals


  • Animals can reproduce by two modes:

Sexual reproduction and asexual reproduction

  • The fusion of male and female gametes fuses to form a zygote and then make an offspring and this process is known as sexual reproduction.
  • Ovaries, oviducts and uterus are the female reproductive organs.
  • Testis, sperm ducts and penis are the male reproductive organs.
  • Female gamete is produced by ovary which is called as ova and the male gamete is produced by testis called sperms.
  • The fusion of male and female gamete is called fertilization.
  • Zygote is the fertilized egg.
  • Fertilization takes place inside the female body is called as internal fertilization.
  • Fertilization that takes place outside the female body is known as external fertilization. Mainly occurs in frog, fish etc.
  • Zygote divide in a repeating manner to give rise to an embryo.
  • Foetus is the stage of embryo in which all body parts are identifiable.
  • Viviparous animals are those who give birth to their young one. For example: humans.
  • Oviparous animals are those which lay eggs.
  • Through drastic changes; the transformation of larva into adults is called metamorphosis.
  • The type of reproduction in which only a single parent is involved is called asexual reproduction.
  • Binary fission is the type of asexual reproduction which generally occur in amoeba, it reproduces by dividing itself into two. 

Exercise 1 ( Page No. : 113 )
Q:
A:

Importance of reproduction in the organisms are as follows:

  1. Reproduction is termed as the biological process in which organisms gives birth to the young ones or their offspring.
  2. It helps in maintaining the continuity of a particular race and helps in increasing the population of the species.
  3. Reproduction is meant for the survival of all living organisms.

Exercise 1 ( Page No. : 113 )
Q:
A:

Fusion of male and female gamete is called fertilization. Both male and female gametes are released by the reproductive organs of male and female body respectively. Sperm is released from the male reproductive organ, i.e. penis. These released sperms enter into the female body through vagina. Then through the vagina, sperms reaches to egg through the fallopian tube. The process of fertilization take place in the fallopian tube. 

fertilization


Exercise 1 ( Page No. : 113 )
Q:
A:

(a)  (i) in the female body

Fertilization occurs internally as well as externally. External fertilization generally occurs in frogs, fishes etc.

(b)  (ii) metamorphosis

Due to drastic changes, larva changes into an adult, this process is known as metamorphosis.

(c)  (ii) one

Only one nuclei is present in a zygote.


Exercise 1 ( Page No. : 113 )
Q:
A:

(a) False

This statement is false because oviparous animals lay eggs and viviparous animals give birth to young ones.

(b) True

This statement is true because each sperm is a single cell and an egg is also a single cell.

(c) True

External fertilization takes place outside the female body; they lay eggs and then eggs got hatch and young ones are produced. So, this statement is true that external fertilization takes place in frogs.

(d) False

This statement is false because a new human individual develops not from a cell called gamete. A new individual is formed due to the fusion of two single cells i.e. sperm and egg.

(e) True

Yes, this statement is true because egg is a single cell.

(f) False

This statement is false because amoeba reproduce by binary fission. It is a type of asexual reproduction.

(g) False

This statement is false because fertilization only occurs in sexual reproduction, not in asexual reproduction.

(h) True

This statement is true because asexual reproduction is that in which only single parent is involved. Binary fission, budding are the types of asexual reproduction.

(i) True

Fusion of male and female gamete occurs and forms an zygote. This process of fusion is known as fertilization.

(j) False

This statement is false because embryo is formed by the repeated divisions of zygote or we can say that embryo is the mature zygote.  


Exercise 1 ( Page No. : 113 )
Q:
A:

                              Zygote

                                       Foetus

It is the union of sperm cell and the egg cell that forms the zygote.

It is the unborn offspring of an animal that develops from an embryo.

It is also known as fertilized ovum.

It refers to the final stage of baby’s development.

Exercise 1 ( Page No. : 113 )
Q:
A:

Asexual reproduction may be defined as the reproduction in which only one parent is involved. The produced offspring is an exact copy of their parent or we can say identical to their parent.

Two methods of asexual reproduction in animals:

  1. Binary fission: It is type of asexual reproduction in which a single cell divides into two halves. For example: Amoeba, bacteria etc.

In Amoeba, one nuclei is divided into two nuclei then the division of body occur in two halves. Each half of the amoeba gets a nuclei and produces new organism by each half.

          binary fission

          2. Budding: This is a type of asexual reproduction in which bulges arises from the parent body. For example: Hydra. The bulges are known as bud.

In Hydra, cells divide rapidly and some buds arise from specific site. These buds arise into a small individual when attached to the parent plant. When these becomes mature, they get detached from the parent body and become an independent individual.

          budding


Exercise 1 ( Page No. : 113 )
Q:
A:

The embryo gets embedded into the wall of the uterus. Embryo is the matured zygote. Development of various body parts like hands, head, eyes, legs etc. occur while the embryo still attached to the uterus. When the cells of body parts become identifiable then this is called as zygote.


Exercise 1 ( Page No. : 113 )
Q:
A:

A change in the animal’s body structure through the cell growth and the differentiation by which an animal develops after birth or hatching is known as metamorphosis. Or, we can say transforming of larva into an adult through a biological process is called as metamorphosis. Metamorphosis involved the sudden and abrupt changes in the structure of an animal. For example: frogs, insects etc.

Life cycle of Frog:

It involves mainly three stages:

Egg   →   Tadpole   →   Adult

life cycle of frog

From the egg tadpole emerges which have gills, tail and a small circular mouth. Tadpole can swim in water freely. Now some sudden and abrupt changes occurs in the structure of tadpole and it develops into a mature frog. The process of metamorphosis starts with the development and finally tail appearance occurs by the body.


Exercise 1 ( Page No. : 113 )
Q:
A:

                   Internal fertilization

                     External fertilization

Fusion of male and female gametes that takes place inside the body is known as internal fertilization.

Fusion of male and female gametes that takes place outside the body is known as external fertilization.

In this, they give birth to the young ones directly.

In this, the organisms first lay down eggs and then they take care of them till the time of hatching at the particular place and after the hatching, the young ones arrive.

It occurs in animals that includes cows, hens, dogs and includes mammals also.

It occurs in aquatic animals like frog, fish, starfish etc.

 


Exercise 1 ( Page No. : 113 )
Q:
A:

Across

     1. FERTILIZATION
     6. INTERNAL
     7. BUDS
     8. OVARY

Down

     2. TESTES
     3. ZYGOTE
     4. OVIPAROUS
     5. BINARY

word puzzle


Exercise 50
Q:
A:

In Vitro Fertilisation


Exercise 50
Q:
A:

Test tube babies are born through IVF technique.


Exercise 50
Q:
A:

As a result of fertilisation zygote is formed which begins to develop into an embryo. The zygote divides repeatedly to give rise to a ball of cells. The cells then begin to form groups that develop into different tissues & organs of the body. This developing Structure is called an embryo. The embryo gets embedded in the wall of the uterus for further development.


Exercise 50
Q:
A:

There are mainly three distinct stages:

        Egg  →  Tadpole (larva)  →  Adultes 

Tadpole look different from the but after sometimes  tadpoles converted are into an frog.

In frogs, the gills of tadpoles are replaced by lungs in adults.


Exercise 50
Q:
A:

"IVF” is an artificial type of fertilization. Some  women's Oviducts are blocked. These women are unable to bear babies because sperms can't reach the egg for fertilisation 

In such cases, doctors collect Freshly released eggs, sperms & keep them together for few hours for IVF. In case fertilisation occurs, the zygote is allowed to develop for about a week & then it is placed in the mother's uterus .Complete development takes place in the uterus & the baby is born like any other baby Babies born through this technique are called test tube babies.


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