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Chapter 4

Reproduction in Humans

Class 8 - Living Science Biology Ratna Sagar


Check your progress 1

Question 1

A ............... is formed as a result of fertilization.

Answer

A zygote is formed as a result of fertilization.

Question 2

The male gametes are called ............... .

Answer

The male gametes are called sperm.

Question 3

The sperm travel through the sperm duct or vas deferens to reach the ............... .

Answer

The sperm travel through the sperm duct or vas deferens to reach the urethra.

Question 4

The ............... are almond-sized oval glands situated in the pelvic or hip region.

Answer

The ovaries are almond-sized oval glands situated in the pelvic or hip region.

Question 5

The cervix is narrow and opens to the outside through a muscular tube called the ............... .

Answer

The cervix is narrow and opens to the outside through a muscular tube called the vagina.

Check your progress 2

Question 1

Human fertilization occurs in the ............... and the baby develops in the ............... .

Answer

Human fertilization occurs in the fallopian tube and the baby develops in the uterus.

Question 2

The foetus is connected to the uterus by a structure called ............... .

Answer

The foetus is connected to the uterus by a structure called placenta.

Question 3

............... fluids acts like a cushion and protects the developing foetus in the uterus.

Answer

Amniotic fluid acts like a cushion and protects the developing foetus in the uterus.

Question 4

From the third week of development till the end of the second month, the developing organism is referred to as the ............... .

Answer

From the third week of development till the end of the second month, the developing organism is referred to as the embryo.

Question 5

The time period between fertilization and birth is called ............... .

Answer

The time period between fertilization and birth is called gestation.

Tick the most appropriate answer

Question 1

External fertilization occurs mostly in

  1. human beings
  2. frogs
  3. snake
  4. birds

Answer

frogs

Reason — External fertilization is seen in aquatic habitats, for example in fishes and frogs.

Question 2

Sperms are produced by

  1. urethra
  2. ureter
  3. testes
  4. ovaries

Answer

testes

Reason — Sperms are produced in a pair of special reproductive organs called testes.

Question 3

Testes are present in a sac called

  1. sternum
  2. scrotum
  3. sperm duct
  4. semen

Answer

scrotum

Reason — Testes are located outside the abdomen in a sac-like structure called scrotum.

Question 4

The sperms reach the urethra by travelling through the

  1. scrotum
  2. testes
  3. sperm duct
  4. vagina

Answer

sperm duct

Reason — The sperms travel through the sperm duct or vas deferens to reach the urethra.

Question 5

The release of an egg from an ovary is called

  1. fertilization
  2. menopause
  3. menstruation
  4. ovulation

Answer

ovulation

Reason — The release of a mature egg from an ovary is called Ovulation.

Question 6

In human females, fertilization of egg takes place in

  1. ovary
  2. uterus
  3. vagina
  4. fallopian tubes

Answer

fallopian tubes

Reason — Fertilization takes place in the fallopian tubes or oviducts of the human females.

Question 7

From the third week of development till the end of the second month of pregnancy, the developing organism is called

  1. infant
  2. embryo
  3. foetus
  4. zygote

Answer

embryo

Reason — From the third week of development till the end of the second month of pregnancy, the developing organism is called embryo. From the third month until birth, it is called foetus.

Question 8

The female sex hormones secreted by the ovaries are

  1. progesterone and testosterone
  2. progesterone and oestrogen
  3. thyroxine and testosterone
  4. oestrogen and testosterone

Answer

progesterone and oestrogen

Reason — The two main functions of ovaries are to produce eggs or ova and secrete female sex hormones progesterone and oestrogen.

Fill in the blanks

Question 1

When an ovum fuses with a sperm outside the body, it is called ............... fertilization.

Answer

When an ovum fuses with a sperm outside the body, it is called external fertilization.

Question 2

Testes produce male sex hormone called ............... .

Answer

Testes produce male sex hormone called testosterone.

Question 3

Fertilization of the ovum takes place in the ............... .

Answer

Fertilization of the ovum takes place in the fallopian tubes.

Question 4

The females have 28 day-long reproductive cycle called ............... .

Answer

The females have 28 day-long reproductive cycle called menstrual cycle.

Question 5

The embryo is attached to the uterus by a structure called ............... .

Answer

The embryo is attached to the uterus by a structure called placenta.

Write true or false. Correct the false statements.

Question 1

Sexual reproduction involves the fusion of an egg and a spore.

Answer

False

Corrected Statement — Sexual reproduction involves the fusion of an egg and a sperm.

Question 2

The ovum is carried from the ovary to the uterus by the vas deferens.

Answer

False

Corrected Statement — The ovum is carried from the ovary to the uterus by the fallopian tubes or oviduct.

Question 3

Oestrogen is a female sex hormone.

Answer

True

Question 4

Normally, two eggs are released from one of the ovaries every month.

Answer

False

Corrected Statement — Normally, one egg is released from one of the ovaries every month.

Question 5

The formation of an individual from the zygote is called development.

Answer

True

Match the following

Question 1

Sl.
No.
Column AColumn B
1.gestationthe lower part of the uterus
2.testosteronethe time period between fertilization and birth
3.spermwhen a sperm fuses with an ovum inside the female body
4.internal fertilizationthe male sex hormone produced by the testes
5.cervixthe male reproductive cells in human beings

Answer

Sl.
No.
Column AColumn B
1.gestationthe time period between fertilization and birth
2.testosteronethe male sex hormone produced by the testes
3.spermthe male reproductive cells in human beings
4.internal fertilizationwhen a sperm fuses with an ovum inside the female body
5.cervixthe lower part of the uterus

Define the following

Question 1

Ovulation

Answer

Ovulation — The release of a mature egg from an ovary is called ovulation.

Question 2

Menstruation

Answer

Menstruation — Discharge of blood along with the broken lining of uterine tissues in females is called Menstruation.

Question 3

Fertilization

Answer

Fertilization — The fusion of male and female gametes i.e. sperm and ova, either inside or outside the body of the female is called Fertilization.

Question 4

Foetus

Answer

Foetus — From the third month of development until birth, the developing organism in the uterus is known as Foetus.

Differentiate between

Question 1

External fertilization and internal fertilization

Answer

Sl.
No.
External fertilizationInternal fertilization
1.When the sperm fuses with the ovum outside the female body it is called external fertilization.When the sperm fuses with the ovum inside the female body it is called internal fertilization.
2.It is seen in aquatic habitat, for example fish and frog.It is found in mammals, birds and reptiles.

Question 2

Testes and Ovary

Answer

Sl.
No.
TestesOvary
1.Testes are part of the male reproductive system.Ovaries are part of the female reproductive system.
2.Testes are located outside the abdomen in a sac-like structure called scrotum.The ovaries are situated in the pelvic or hip region.
3.Sperms are produced in testes.Eggs (ova) are produced and released by ovaries.

Question 3

Sperm and ovum

Answer

Sl.
No.
SpermOvum
1.The male gamete is called sperms.The female gamete is called ovum.
2.Sperms are formed in testes.Ovum is formed in ovaries.
3.Sperm pass through sperm duct.Ovum moves through fallopian tube.
4.Sperms have oval head and long tail.Ovum is generally spherical and is full of yolk.

Answer the following in short

Question 1

Define fertilization.

Answer

The fusion of male and female gametes i.e. sperm and ova, either inside or outside the body of the female is called Fertilization.

Question 2

Name the male reproductive organs of human beings.

Answer

The male reproductive organs of human beings are

  1. a pair of testes
  2. sperm ducts
  3. urethra
  4. penis
  5. accessory glands

Question 3

Name the male reproductive organ through which sperms are released.

Answer

Penis is the male reproductive organ through which sperms are released.

Question 4

What is semen?

Answer

The mixture of the sperms and secretions from the accessory glands is called semen.

Question 5

Which part of the human body produces ova?

Answer

Ovaries produce ova.

Question 6

Name the organ where the fertilization of an ovum by the sperm takes place.

Answer

Fallopian tube or Oviduct.

Question 7

What do you mean by foetus?

Answer

From the third month of development until birth, the developing organism in the uterus is known as Foetus.

Question 8

What is placenta?

Answer

The structure which connects the foetus to the uterus and helps the foetus to get oxygen and nutrients from mother is called placenta.

Answer the following in detail

Question 1

Write about different parts of the male reproductive system of human beings.

Answer

The male reproductive system of human beings consists of a pair of testes, sperm ducts, urethra, penis and accessory glands. Each of them is briefly described below:

  1. Testes — Testes are located outside the abdomen in a sac-like structure called scrotum. They are the primary reproductive organs of the male reproductive system. They produce the male gametes called sperms.
  2. Sperm Ducts — The sperms produced in the testes, travel through the sperm duct or vas deferens to reach the urethra.
  3. Accessory Glands — As the sperms pass through the sperm duct, secretions from the accessory glands are mixed with them. This mixture is called semen.
  4. Urethra — It is a tube through which urine and semen passes.
  5. Penis — Through penis, sperms are discharged and deposited into the vagina of the female body. In males, the penis is the organ used both for the discharge of the urine and the sperms.

Question 2

Explain the process of fertilization in human beings.

Answer

In human beings, fertilization takes place in the fallopian tubes or oviducts inside the female body. The sperms from the male received by the vagina swim up to the oviduct for fertilization. An ovum is fertilized by a single sperm. It results in the formation of a single cell called zygote. Since the zygote is formed as a result of the fusion of sex cells from the father and mother, it has the chromosomes and genes from both of them. Thus, the new individual inherits characteristics from both the parents. Zygote moves from the oviduct to the uterus and gets implanted in it for further development. The below diagram shows the process of fertilization in human beings:

Explain the process of fertilization in human beings. Reproduction in Humans, Living Science Biology Ratna Sagar Solutions ICSE Class 8.

Question 3

Explain the process of development of a zygote into a foetus.

Answer

The formation of an individual from the zygote is called development. In human beings, the zygote undergoes continuous cell division to form a ball of cells. The ball gets implanted in the uterine wall for further development. The implanted ball of cells undergoes many cell divisions. The cells change their size, shape and function to become different types of cells such as nerve cells and blood cells. From these, tissues and organs develop and get organized into various organ systems of the baby. From the third week of development till the end of the second month, the developing organism is referred to as the embryo. From the third month until birth, it is called foetus.

Question 4

What is placenta? How is the placenta beneficial to the foetus?

Answer

The structure which connects the foetus to the uterus and helps the foetus to get oxygen and nutrients from mother is called placenta. Placenta is an organ attached to the lining of the uterus.

The placenta is beneficial to the foetus in following ways:

  1. The developing foetus receives essential nutrients and oxygen from the mother.
  2. Carbon dioxide and other wastes from the foetus also pass into the mother's blood through the placenta.

Think and Answer

Question 1

Can menstruation and ovulation occur till the birth of the baby during pregnancy.

Answer

No, menstruation and ovulation does not occur during pregnancy. As the embryo gets implanted into the uterus, the uterine wall is not shed so menstruation does not occur. Also, ovary does not release a new egg during pregnancy so ovulation does not occur.

Number the Process

Question 1

Number the process in the correct sequence of their occurrence.

implantation, embryonic development, fertilization, birth, ovulation

Answer

The Correct sequence is as follows:

  1. ovulation
  2. fertilization
  3. implantation
  4. embryonic development
  5. birth

Complete the Table

Question 1

Complete the following table by filling in the blanks numbered 1 to 5.

Sl.
No.
StructureFunction
1.ovaries1
2.uterus2
3.3produces sperm
4.fallopian tubes4
5.5foetus is connected to the placenta through this

Answer

The completed table is shown below:

Sl.
No.
StructureFunction
1.ovariesproduce eggs (1)
2.uteruszygote developes into baby in uterus (2)
3.Testes (3)produces sperm
4.fallopian tubesFertilization and transfer of zygote to the uterus (4)
5.Umbilical cord (5)foetus is connected to the placenta through this

Correct the Incorrectly Labelled Parts

Question 1

Some of the parts of the female reproductive system are marked incorrectly. Write the correct names in the space provided.

Some of the parts of the female reproductive system are marked incorrectly. Write the correct names in the space provided. Reproduction in Humans, Living Science Biology Ratna Sagar Solutions ICSE Class 8.

Answer

oviducts → ovaries

uterus → fallopian tube or oviduct

vagina → uterus

ovary → vagina

Male Reproductive System Outline

Question 1

Given alongside is the outline of the cross-section of the male reproductive system.

Given alongside is the outline of the cross-section of the male reproductive system. Label the following parts. Name the hormone produced by the testes. Where are the testes located? Reproduction in Humans, Living Science Biology Ratna Sagar Solutions ICSE Class 8.
  1. Label the following parts.
    1. testes
    2. urethra
    3. penis
    4. vas deferens
  2. Name the hormone produced by the testes.
  3. Where are the testes located?

Answer

  1. The labelled diagram is shown below:
Given alongside is the outline of the cross-section of the male reproductive system. Label the following parts. Name the hormone produced by the testes. Where are the testes located? Reproduction in Humans, Living Science Biology Ratna Sagar Solutions ICSE Class 8.
  1. Testosterone
  2. Testes are located outside the abdomen in a sac-like structure called scrotum.
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