Selina ICSE Class 8 Biology Solutions Chapter 3 Reproduction in Humans

Selina ICSE Solutions

Multiple Choice Questions:

Question 1. Put a tick mark (✓) against the correct alternative in the following statements:

(1) The testes are located within the:
a. Penis
b. Scrotum
c. Ureter
d. Urinary bladder
Solution: (b) Scrotum

(2) Amoeba is most commonly reproduced by:
a. Budding
b. Regeneration
c. Binary fission
d. Multiple fission
Solution: (c) Binary fission

(3) Identify the stage which is formed after the fertilisation of the egg by the sperm?
a. Ovule
b. Foetus
c. Embryo
d. Zygote
Solution: (d) Zygote

(4) Internally, the uterus opens into:
a. Urethra
b. Vagina
c. Oviduct
d. Vulva
Solution: (b) Vagina

(5) Which one of the following represents the correct sequence in the life history of a butterfly?
a. Egg → Larva → Adult → Pupa
b. Egg → Pupa → Adult → Larva
c. Egg → Larva → Pupa → Adult
d. Egg → Pupa → Larva → Adult
Solution: (c) Egg → Larva → Pupa → Adult

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.

Selina ICSE Class 8 Biology Solutions Chapter 3 Reproduction in Humans

Question 2. Define the following terms:
(a) Fetilization
(b) Implantation
(c) Puberty

(a) Fertilization: The process of fertilization, in which sperm and eggs from opposing partners (male and female) combine to generate a zygote. It’s known as fertilization.
(b) Implantation: By the time the fertilised egg (zygote) enters the uterus, a little ball of many cells has already begun to form.
(c) Puberty: Boys and females go through puberty during which their reproductive systems develop. The growth of breasts is the earliest sign of puberty in girls and it begins around the age of ten. The earliest sign of it in boys is an enlargement of the testicles, which appears around the age of 11 years old. In a sudden growth spurt, the shoulder girdle expands more than the hip waist.

Question 3. State the reason why testes lie outside the abdomen in a scrotum?

The scrotum’s smooth muscular tissues retain the testes at a cooler temperature than the body temperature, which is 2°C to 3°C lower than the body temperature and the temperature that is most conducive to sperm generation. Both testes remain in the scrotum because normal body temperature is too high.

Question 4. Why is it important that a very large number of sperms should be present in the semen?

Semen contains 20,000,000 to 40,000,000 sperms every orgasms. Only one or two sperms, however, enter the ovum and fertilise the egg, creating the zygote. It creates the embryo from which people are born. Semen quality includes both sperm quantity and quality because the sperm in the semen is what really matter.

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.

Sperms are produced in testes. They pass as follows: The testes consist of a mass of sperm producing tube. The tubes join to form ducts leading to the epididymis which in.turn leads into a muscular sperm duct. The two sperm ducts, one from each testes, open at the top of the urethra.

Question 6. State the functions of the following:
(a) Ovary
(b) Testes
(c) Fallopian tubes
(d) Seminal vesicle
(e) Uterus

(a) Ovary: Ovaries emit the female sex hormones oestrogen and progestrone in addition to ova (eggs).
(b) Testes: Male humans have two testicles. Sperm are created in the testes.
(c) Fallopian tubes: The female reproductive system of humans has two fallopian tubes. Within the fallopian tube, fertilisation takes place. The uterus receives the fertilised egg as well.
(d) Seminal vesicle:- The seminal vesicle, which serves to both secrete seminal fluid and store sperm.
(e) Uterus:- The inner lining of the uterus receives, safeguards, and nourishes the embryo. During birth, contractions of the muscle wall expel the baby.

Question 7. Given here is a section of the female reproductive system of human beings.
(a) Name the parts labelled 1 to 4
(b) Name the part where fertilisation occurs in human beings.

Selina ICSE Class 8 Biology Solutions Chapter 3 Reproduction in Humans


Selina ICSE Class 8 Biology Solutions Chapter 3 Reproduction in Humans

(b) In the top portion of the oviduct, fertilisation takes place. Fertilization is the process through which the sperm and the egg combine to generate a zygote.

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.

Selina ICSE Class 8 Biology Solutions Chapter 3 Reproduction in Humans


Selina ICSE Class 8 Biology Solutions Chapter 3 Reproduction in Humans

1. Seminal vesicle: The seminal vesicles secrete a substance that acts as a vehicle for the sperm’s movement.
2. The prostate gland: The prostate gland that secretes a fluid called into the semen as it travels through the urethra.
3. Testes: The testes are where sperm are made.
4. Urethra: Urine or semen can be carried by the urethra, which goes through the penis.
5. Sperm duct: sperm passes through the sperm duct.

Long Answer Questions:

Question 1. Define the term metamorphosis. Briefly describe the various stages occurring in the life cycle of a butterfly.

Metamorphosis: A change in an animal’s form and frequently behaviour that occurs during normal development after the animal has gone through two or more different stages of transformation from an immature form to an adult form.
Butterfly life cycle: On the plant leaves, the butterfly lays its eggs. Larva is the term for the young that emerges from the egg. It goes through many developmental stages. Butterfly larvae are sometimes known as caterpillars. It moves a lot. It has a huge appetite. It consumes food, moves aggressively, and enlarges.

Selina ICSE Class 8 Biology Solutions Chapter 3 Reproduction in Humans

It is known as a pupa and ceases moving and feeding. It is a stage of repose. The pupa rotates thread around itself, encasing it in a shell. It is known as a cocoon. This cocoon serves as a protective shell for the pupa. It develops the characteristics of an adult at this period. When the pupa reaches adulthood, it breaks out of the cocoon and emerges as an adult butterfly. The newly emerging butterfly has delicate, wrinkled wings. These have fully expanded after an hour, at which point it begins to fly.

Question 2. What is fertilization? Describe the process in human beings.

The fusion of male (sperm) and female (ova) gamete is called fertlization. As the male performs sexual act with the female and as a result of it the semen is deposited in the vagina of the female. Thus the semen has millions of sperms. Only a few of these sperms are able to reach the upper part of the oviduct. If there is an egg in the oviduct it is fertilized by the sperm. As sperm enters the egg and this leads to the formation of zygote, this act is called fertilisation. During fusion only the head part of the sperm, which has nucleus, enters the egg. The tail is left behind. The nucleus of the sperm and egg fuse and form the zygote. Soon this zygote becomes many called embryo and reaches the uterus and implants on the wall of the uterus and forms the foetus. Baby develops with in the gestation period of 280 days. After this the baby is delivered.

Question 3. How does a single called fertilized egg grows into an adult in human beings?

The zygote, or fertilized egg, splits and redivides to produce a ball of cells. This particular type of embryo enters the uterus and attaches to the uterine wall. Implantation is the process by which an embryo is fixed to the uterus. The embryo is currently going through a phase called “cell specialisation.” It causes the development of various bodily parts.
Differentiation is the name given to this process. It results in the development of different tissues and organs, and as a result, organ systems are created. Organ systems play a role in the development of an individual. As a result, the zygote creates an embryo, a child, and an adult.

Question 4. Tabulate the important physical changes in the boys and girls that take place during puberty.

Reproductive system of boys and girls mature during puberty. Puberty starts at 10 in girls and at 11 in boys. Testes enlarge in boys and breasts develop in girls. The following table shows the physical changed in boys and girls that take place during puberty.

Selina ICSE Class 8 Biology Solutions Chapter 3 Reproduction in Humans

Question 5. Describe the human female reproductive system with a labelled diagram.

On each side of the uterus lie two whitish oval bodies called ovaries. Ovaries produce eggs. Only one egg is produced by an ovary alternatively every month. A pair of narrow, muscular, long ducts extend from each ovary to the upper part of the uterus. These are called the oviducts or fallopian tubes. The mouth of these oviducts is expanded to form a funnel shaped structure.
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.
The uterus opens to the outside through a long, muscular tube called vagina, situated between the rectum and the urethra.

Selina ICSE Class 8 Biology Solutions Chapter 3 Reproduction in Humans

Question 6. ‘Adolescence is a crucial stage’. Justify this statement.
During adolescence physical and emotional changes takes place in the body of boys and girls. This is period between the age of 10 to 19 and this is very critical period. Boys possess a muscular build, facial hair, body hair in the armpits, body hair on the genital organs, and a raspy voice. The girls’ large lips, raised breasts, and high-pitched voices are among their other attractive features. In all situations, the body gets longer. Both boys and girls become aware of how their bodies are changing. To each other, they show uncertainty and shyness. They start to feel self-conscious about their bodies and spend a lot of time getting ready. Their body’s hormone levels rise, which causes them to feel restless. Their emotions and moods are regulated by hormones, which have an impact on their brains. They enjoy spending time with people of their own sex and exhibit attraction to those of the other sex. Therefore, it is a very odd and important time in their lives.

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