Q.1.a. How many spermatozoa does one secondary spermatocyte produce?
b. Where in zygote does the first cleavage division occur?
Answer- a. The secondary spermatocytes undergo meiotic division – II to generate four haploid spermatids which through the process of spermiogenesis are transformed into spermatozoa.
Answer- b. Cleavage occurs within the fallopian tube and is holoblastic, dividing the zygote completely into blastomeres. The first cleavage divides the zygote longitudinally into two blastomeres wherein one is slightly larger than the other.
Q.2. State the significance of the following stages during the lifetime of a female.
- Menarche
- Menopause
Answer- The first menstruation or onset of menstruation at puberty is referred to as menarche. It indicates the attainment of sexual maturity and the commencement of the fertile period. Menstruation cycle is the cycle of events from one up till the next menstruation and is repeated for about 28 days on an average wherein one ovum is released. Menopause, on the other hand, is when the menstruation cycle comes to a halt, indicating the end of the fertile period as the process of ovulation stops. Cyclic menstruation denotes a regular reproductive phase stretching from menarche to menopause.
Q.3. Why does corpus luteum stay active throughout pregnancy and in the absence of fertilization, is active only for 10-12 days?
Answer- During the luteal phase, the leftover parts of Graafian follicle transform into the corpus luteum. It discharges large quantities of progesterone hormone which is required for the maintenance of the endometrium. The endometrium is important for implantation of the fertilized egg and various other stages of pregnancy. Hence corpus luteum has a long life in pregnancy. In the absence of fertilization, upholding of the corpus luteum is not required and thus it declines within 10-12 days, which causes the lining of the endometrium to menstruate and hence the onset of the new menstrual cycle.
Q.4. What is foetal ejection reflex? How does it cause parturition?
Answer- Foetal ejection reflex is the mild uterine contractions that arise from the parturition signals from the fully developed fetus and the placenta. This reflex stimulates the release of oxytocin, which causes uterine contractions, in turn, stimulating the increased secretion of oxytocin. This action of uterine contractions and oxytocin secretion further results in stronger contractions leading to the dilation and hence expulsion of the baby out of the uterus through the cervical canal, expelling placenta along, thus the parturition or childbirth.
Q.5. What are the functions of placenta other than its endocrine function?
Answer- The placenta promotes the supply of nutrients and oxygen to the embryo. It also facilitates the elimination of excretory wastes and carbon dioxide produced by the embryo. Placenta aids in the transportation of substances to and from the embryo as it is connected to the embryo through the umbilical cord.
Q.6. Why is breastfeeding recommended during the initial stages of infant growth?
Answer- The mammary glands in females start producing milk towards the end of pregnancy through the process of lactation which helps the mother feed the newborn. Colostrum is the milk produced during the initial few days. Colostrum contains antibodies which are crucial in developing resistance in the newborns hence it is recommended by doctors to bring up a healthy baby.
Q.7. What are the different stages of the follicular phase of the menstrual cycle taking place in ovary and uterus?
Answer- In this phase, primary follicles transform into the fully mature Graafian follicle in the ovary. The endometrium of the uterus simultaneously regenerates through proliferation. Changes in the levels of ovarian and pituitary hormones induce changes in the uterus and ovaries. During this stage, the secretion of FSH and LH eventually increases and triggers the secretion and follicular development of estrogen by the growing follicles. In the middle of the cycle, both LH and FSH reach the peak level. This speedy secretion of LH at the maximum level during the mid-cycle causes rupture of Graafian follicle and hence ovulation.
Q.8. Define Parturition?
Answer-. Parturition refers to a process of delivering a baby from the uterus to the vagina to the outside world. There are three stages of Parturition:
1. Dilation.
2. Expulsion.
3. Placental.
Q.9. Define Fertilization?
Answer-. Fertilization refers to the biological process of fusion of male and female gametes resulting in the formation of a zygote. In humans, the fertilization process takes place in the fallopian tube.
Q.10. Write the main functions each of testis and ovary?
Answer-. Testis also called as the Testicles. It is a pair of oval-shaped organs masked in a pouch called the scrotum. They are responsible for the production of sperms and the male hormone testosterone.
The ovary is a ductless reproductive gland, which functions by producing a female sex hormone called estrogen and also involved in producing and storing the ovum or the egg cell.
Easy Biology 