Summative Practice 15 – Question 5 & 6 (Form 4 Biology Textbook Exercise and Answer)

Question 5:
State the changes that occur to a zygote from fertilisation up to birth.

The zygote divides repeatedly by mitosis. This cellular division produces a ball of cells, but the cell size is retained at this stage. Further development produces a solid ball of cells called morula. Then the morula will form a blastocyst, a hollow sphere consisting of cells. After a few days, the blastocyst will implant itself on the endometrium (uterine wall) of the mother. This is where the blastocyst continues its development as an embryo. After two months, the embryo is called foetus with most body parts identifiable. The foetus is known as a baby after birth.

Question 6:
A woman took contraceptive pills to prevent pregnancy. The pill inhibits secretions of the Follicle Stimulating Hormone (FSH) from the pituitary gland. Explain the effects of taking contraceptive pills on the menstrual cycle.

• Level of FSH is low (in the blood).
• No development of follicle and Graafian follicle is not formed.
• Less oestrogen secreted (by ovary).
• Pituitary (gland) is not / less stimulated to secrete (enough) LH.
• No ovulation.

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