CBSE Class 12 Biology Human Reproduction Worksheet Set 04

 

Very Short Answer Questions

Question. Mention the location and the function of Leydig cells in humans.
Answer. Leydig cells are present in the regions called interstitial spaces outside the seminiferous tubules.
They synthesise and secrete androgens (testosterone).

Question. Mention the function of mitochondria in sperm. 
Answer. Provide energy for the movement of sperm tail.

Question. Identify the figure given below and the part labelled “A”. 

Answer. The figure is of blastula/blastocyst.
A—Trophoblast.

Question. When do the oogenesis and the spermatogenesis initiate in human females and males respectively? 
Answer. Oogenesis in human females initiate at the foetal/embryonic stage.
Spermatogenesis in human males starts at puberty.

Question. What is the role of cervix of the human female system in reproduction?
Answer. Cervix helps in regulating the passage of sperms into the uterus and forms the birth canal to facilitate parturition.

Question. What are the major functions of male accessory ducts and glands?
Answer. Male accessory ducts include rete testes, vasa efferentia, epididymis and vas deferens. These ducts store and transport the sperms from the testes to the outside through urethra. Male accessory glands include paired seminal vesicles, prostate gland and paired bulbourethral glands. Secretion of these glands constitute the seminal plasma which is rich in fructose, calcium and certain enzymes. The secretions of bulbourethral glands also help in the lubrication of the penis.

Question. Draw a labelled diagram of a section through ovary.
Answer.

Question. Write two major functions each of testis and ovary.
Answer. Functions of testis:
(i) Production of sperms by seminiferous tubules.
(ii) Production of male sex hormone, testosterone, by Leydig cells.
Functions of ovary:
(i) Production of ova (eggs).
(ii) Production of female sex hormones, estrogen and progesterone.

Question. Draw a labelled diagram of a Graafian follicle.
Answer.

Short Answer Questions

Question. Why are the human testes located outside the abdominal cavity? Name the pouch in which they are present. 
Answer. The human testes need lower temperature, 2 – 2.5°C less than the body temperature, for the formation of sperms which is provided outside the body.
Testes are present in scrotal sac or scrotum.

Question. (i) How many spermatozoa are formed from one secondary spermatocyte?
(ii) Where does the first cleavage division of zygote take place? 
Answer. (i) Two
(ii) During the passage of zygote from fallopian tube to the uterus.

Question. Draw a diagram of a human sperm. Label only those parts along with their functions, that assist the sperm to reach and gain entry into the female gamete. 
Answer. 

Question. Given below is a flow chart showing ovarian changes during menstrual cycle. Fill in the spaces with the hormonal factor(s) responsible for the events shown. 

Answer. a: FSH and estrogen
b: LH
c: Progesterone

Question. Differentiate between major structural changes in the human ovary during the follicular and luteal phase of the menstrual cycle.
Answer. 

S.No.	Follicular phase	Luteal phase
(i)	During this, primary follicles grow to become fully mature Graafian follicle	During this, remaining part of Graafian follicle transforms into corpus luteum.
(ii)	Endometrium regenerates through proliferation.	Endometrium further thickens secreting progesterone for implantation after fertilisation.If fertilisation does not occur, corpus luteum degenerates.

Question. Where is acrosome present in humans? Write its function. 
Answer. Acrosome is present on the sperm head. It has enzymes to help the sperm enter into the cytoplasm of ovum through zona pellucida and plasma membrane to facilitate entry of sperm nucleus for fertilisation.

Question. Write the function of each of the following:
(a) Middle piece in human sperm.
(b) Luteinising hormone in human males. 
Answer. (a) Provides energy for movement as it contains mitochondria.
(b) Stimulates synthesis and secretion of androgens or male hormones for spermatogenesis.

Question. What is spermatogenesis? Briefly describe the process of spermatogenesis.
Answer. The process of formation of spermatozoa (sperms) from diploid spermatogonia is called spermatogenesis. The male germ cells of seminiferous tubules multiply mitotically to increase in numbers. Spermatogonia grow and increase in size to form primary spermatocyte (2n). The primary spermatocytes undergo the first meiotic division and produce two haploid secondary spermatocytes (n). Each secondary spermatocyte undergoes the second meiotic division and produces 4 equal haploid spermatids. The spermatids are finally transformed into spermatozoa by the process of spermiogenesis.

Question. Define spermiogenesis and spermiation.
Answer. Spermiogenesis: The process involving transformation of spermatids into spermatozoa is called spermiogenesis.
Spermiation: After spermiogenesis, sperm heads become embedded in the Sertoli cells and are finally released from the seminiferous tubules by the process called spermiation.

Please click on below link to download CBSE Class 12 Biology Human Reproduction Worksheet Set D