Selina Concise Class 8 Biology Solution Chapter No. 3- ‘Reproduction in Humans’ For ICSE Board Students.
Selina Concise Biology Solutions for Class 8th Chapter 3 Reproduction in Humans with easy language, expert answers and doubt clearing sections. The book is especially designed keeping in mind the syllabus of ICSE board and the difficulty level faced by the students of ICSE boards Class 8.
Multiple choice questions
1) Put a tick mark against the correct alternative in the following statements.
a) The testes are located within the
i) Penis
ii) Scrotum
iii) Ureter
iv) Urinary bladder
Ans. A pair of testes lie outside the abdominal cavity in a sac called the scrotum.
b) Amoeba most commonly reproduces by
i) Budding
ii) Regeneration
iii) Binary mission
iv) Multiple fission
Ans. Lower organisms like bacteria reproduce by binary fission.
c) Identify the stage which is formed after the fertilization of the egg by the sperm?
i) Ovule
ii) Foetus
iii) Embryo
iv) Zygote
Ans. After the fertilization of an ovum by the sperm, a cell called zygote is formed
d) Internally the uterus opens into:
i) Urethra
ii) Vagina
iii) Oviduct
iv) Vulva
Ans. The uterus opens to the outside through a long muscular tube called vagina, situated between the rectum and the urethra.
Short Answer Questions
1) Distinguish between the following pair of terms:
a) Egg and sperm:
Ans:
Egg | Sperm |
They are called as female gamete. | They are male gamete. |
It is diploid in nature | It is haploid in nature. |
They divide by mitosis | Divide by meiosis. |
b) Sexual reproduction and asexual reproduction:
Ans:
Sexual reproduction | asexual reproduction |
Gametes are fused. | Gametes are not fused. |
Involvement of 2 parents. | No involvement of 2 parents. |
Variations are present. | Variations are not present |
c) Budding and regeneration:
Ans.
Budding | Regeneration |
In this bud are grow from the broken body parts. | In regeneration, broken part of the organism regenerate again. |
For example : Hydra | For example : Planaria |
2) Define the following terms:
a) Fertilization: When the male gamete that is sperm fuses with the female gamete which is ovum in the female reproductive tract, it is known as fertilization.
b) Implantation: The embryo is fixing in the uterus by the natural way is called implantation.
3) State the reason why testes lie outside the abdomen in a scrotum?
Ans. Yes, the testes lie outside the abdomen in a scrotum because, the testes will need an appropriate temperature is 2 – 3⁰ C which is less than that of the body temperature. At this temperature sperm production and development takes place, therefore the testes lie outside the abdomen in a scrotum.
4) Why is it very important that a large number of sperms should be present in the semen?
Ans. Yes, it is very important that a large number of sperms should be present in the semen because when millions of sperms are produced and secreted into the vagina, out of the millions sperms very few reach up to the oviduct and remaining will die during the way. From the few sperms only one will fertilize the ovum.So it is very important that a large number of sperms should be present in the semen.
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.
Ans. Sperm producing tubes —> epididymis —> sperm duct —> urethra.
6) State the functions of the following:
a.) Ovary: The function of the ovaries is to produce eggs and the hormones estrogen and progesterone.
b.) Testes: Testes produce sperms and the hormone testosterone.
c.) Fallopian tubes: They are present in between uterus and ovaries and responsible for transportation of oocytes.
d.) Seminal vesicle : Seminal vesicle responsible for production of semen.
e.) Uterus: The embryo grows and develops inside the uterus.
7) Given here is the structure of female reproductive system in humans.
a.) Name the parts labelled 1 to 4
Ans. 1 – Ovaries 2 – Oviducts 3 – Uterus 4 – Vagina
b) Name the part where fertilization occurs in the female reproductive system.
Ans. Fertilization occurs in the fallopian tubes.
8) Given alongside is a diagram of the male reproductive system in humans.Label the parts indicated by the numbers 1 to 5, and state their functions.
Ans. 1 – Seminal vescicles: They produce a semen and provides medium for the transportation of the sperms.
2) – Epididymis: The mass of sperm producing tubes join to form ducts leading to the highly coiled epididymis.
3) – testes: Sperms are produced in the testes
4) – urethra : The urethra passes through the penis and carries either urine or semen.
5) – sperm duct: The two sperm ducts, one from each testes open into the urethra just below the urinary bladder.
Long Answer Questions
1) How does a single – celled fertilized egg grow into an adult human body?
Ans. In the fertilization, out of million of sperm only one sperm reach upto the ovum. When the one sperm unites with the ovum the fertilization occurs. After fertilization meiotic division occurs and zygote forms. After the formation of zygote the next developmental stages starts and the ferilized egg increase in number of cells and size of the cell, therefore it leads to formation of mass. The developmental stages are morula, blastula and gastrula. The development of cells, tissues, organs and system occurs in the body in the nine months of pregnancy, that’s how a single – celled fertilized egg grow into an adult human body.