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Chapter 3

Reproduction in Humans

Class 8 - Concise Biology Selina


Multiple Choice Questions

Question 1

The testes are located within the:

  1. Penis
  2. Scrotum
  3. Ureter
  4. Urinary bladder

Answer

Scrotum

Reason — Sperms are produced in the testes. A pair of testes lie outside the abdominal cavity in a sac called the scrotum.

Question 2

Amoeba most commonly reproduces by:

  1. Budding
  2. Regeneration
  3. Binary fission
  4. Multiple fission

Answer

Binary Fission

Reason — Binary fission is the most common method of reproduction in single-celled organisms. In Amoeba, it results in the division of the parent amoeba into two daughter amoeba.

Question 3

Identify the stage which is formed after the fertilisation of the egg by the sperm?

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

Answer

Zygote

Reason — A zygote is a fertilised egg. The zygote is formed when the male gamete (sperm) and female gamete (egg) fuse. It's created when sperm meets an egg in one of the fallopian tubes. The zygote grows by cell division and produces an embryo.

Question 4

Internally, the uterus opens into:

  1. Urethra
  2. Vagina
  3. Oviduct
  4. Vulva

Answer

Vagina

Reason — The uterus is a hollow, inverted pear shaped muscular organ which opens to the outside through a long, muscular tube called the vagina, situated between the rectum and the urethra.

Short Answer Questions

Question 1

Distinguish between the following pair of terms:

(a) Egg and sperm

(b) Sexual Reproduction and asexual reproduction

(c) Budding and regeneration

Answer

(a) Difference between Egg and Sperms

EggSperms
Egg is stationary.Sperm is capable of performing locomotion.
Egg has no locomotory organ.Sperm has a special locomotory organ, the tail.
Released one at a time.Released in millions.
The female gamete.The male gamete.

(b) Difference between Sexual Reproduction and Asexual reproduction

Sexual ReproductionAsexual Reproduction
In Sexual Reproduction male and female gametes are involved and fertilised.In Asexual Reproduction male and female gametes are not involved.
Two organisms or parents are involved to produce an organism.A single parent divides itself to two or more number of daughter cells.
This type of reproduction can be seen in higher level organisms.This type of reproduction can be seen in lower level organisms.
E.g: HumansE.g: Amoeba

(c) Difference between Budding and Regeneration

BuddingRegeneration
Budding is a process in which buds grow on the outside of the parents body. The buds detach themselves once they are capable of independent existence.Regeneration is the process of generating lost parts of the body. It is also happens for reproductive purposes. Some organisms, when cut into multiple pieces then each piece develops into a young organism itself.
Budding is exclusively for reproduction.Regeneration is for regrowth of lost body and in some cases also for reproduction.

Question 2

Define the following terms:

(a) Fertilization

(b) Implantation

Answer

(a) Fertilization — The fusion of the male gamete (sperm) and the female gamete (ovum) to form a zygote is called fertilisation.

(b) Implantation — The process of fixing of the fertilized egg (embryo) to the wall of the uterus is termed implantation.

Question 3

State the reason why testes lie outside the abdomen in a scrotum?

Answer

Testes lie outside the body because the normal body temperature does not allow the maturation of the sperms. In such an arrangement, the testes are at a temperature which is 2-3°C lower than that of the body. This is the most suitable temperature for sperm production and development.

Question 4

Why is it important that a very large number of sperms should be present in the semen?

Answer

Semen contains a very large number of sperms because out of the millions of sperms released into the vagina, only a few of them are able to reach up to the upper parts of the oviducts. Some die on the way and are absorbed. Only a few of them reach the ovum. Thus, to increase the chances of fertilisation, a very large number of sperms should be present in the semen.

Question 5

List the structures in their correct sequence through which the sperms must pass from the time they are produced in the testes to the time they leave the urethra.

Answer

Testes → Sperm duct → Urethra

Question 6

State the functions of the following:

(a) Ovary

(b) Testes

(c) Fallopian Tubes

(d) Seminal Vesicles

(e) Uterus

Answer

(a) Ovary — The ovaries have two main reproductive functions in the body. They produce eggs and secrete the reproductive hormones, Oestrogen and Progesterone.

(b) Testes — The two main functions of Testes are to produce and store sperms and to secrete the male reproductive hormone Testosterone.

(c) Fallopian Tubes — Fallopian Tubes transfer the egg from the ovaries to the uterus.

(d) Seminal vesicles — They produce a secretion which serves as a medium for the transportation of the sperms.

(e) Uterus — The embryo grows and develops in the Uterus.

Question 7

Given here is a section of the female reproductive system of humans.

Given here is a section of the female reproductive system of humans. Name the parts labelled 1 to 4. Name the part where fertilisation occurs in the female reproductive system. Reproduction in Humans, Concise Biology Solutions ICSE Class 8.

(a) Name the parts labelled 1 to 4.

(b) Name the part where fertilisation occurs in the female reproductive system.

Answer

(a) The parts are:

  • 1 → Ovary
  • 2 → Fallopian tube
  • 3 → Uterus
  • 4 → Vagina

(b) Fallopian tubes (also called Oviduct)

Question 8

Given alongside is a diagram of male reproductive system in humans. Label the parts indicated by numbers 1 to 5, and state their functions.

Given alongside is a diagram of male reproductive system in humans. Label the parts indicated by numbers 1 to 5, and state their functions. Reproduction in Humans, Concise Biology Solutions ICSE Class 8.

Answer

  • 1 → Seminal vesicle — Produce a secretion which serves as a medium for the transportation of the sperms.
  • 2 → Prostate gland — Pours an alkaline secretion into the semen as it passes through the urethra.
  • 3 → Testes — To produce and store sperms and to secrete the male reproductive hormone Testosterone.
  • 4 → Urethra — Carries either Urine or Semen.
  • 5 → Sperm duct — Carries the sperms from the Epididymis to the Urethra.

Long Answer Questions

Question 1

How does a single-celled fertilized egg grow into an adult in human body?

Answer

The fertilized egg starts developing and by the time it reaches to the uterus from the Oviduct, a small ball of numerous cells is already formed. This is called the embryo. The embryo forms a pit in the wall of the uterus and gets fixed in it. This process is called implantation and it produces the state of pregnancy. The embryo keeps growing in the uterus and specialisation of cells starts, leading to the formation of different parts of the body. This whole process is called differentiation.
By the end of five weeks of pregnancy, the embryo has developed the heart and circulatory system. It is known as foetus now. After two months limbs are also formed. Foetus develops in the uterus for about 280 days. This time period is called gestation. After gestation, birth of the baby happens. The baby is pushed out by the powerful contractions of the muscles of the uterus through the vagina.

Question 2

Describe the human female reproductive system with a labelled diagram.

Answer

The main parts of the human female reproductive system as shown in the diagram below are Ovaries, Oviduct (also called Fallopian tubes), Uterus, Vagina. Each part and its function is described below:

  1. Ovaries — Ovaries are two whitish oval bodies, lying within the lower half of the abdomen, one on either side of the uterus. The function of ovaries is to produce eggs and secrete the female reproductive hormones Oestrogen and Progesterone.
  2. Oviducts (Fallopian tubes) — These are a pair of narrow, muscular, long ducts extending from each ovary to the upper part of the uterus. The mouth of these oviducts is expanded to form a funnel shaped structure. They transfer the egg from the ovaries to the uterus. Fertilisation of the egg takes place here.
  3. Uterus — The uterus is a hollow, inverted pear shaped muscular organ found in the pelvic cavity between the urinary bladder and the rectum. The embryo grows and develops in the uterus.
  4. Vagina — The uterus opens to the outside through a long, muscular tube called vagina, situated between the rectum and the urethra. The vagina receives the male's penis during copulation and also serves as the birth canal.
Describe the human female reproductive system with a labelled diagram. Reproduction in Humans, Concise Biology Solutions ICSE Class 8.
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