Human Reproduction — Part 3: Fertilisation to lactation: visual lesson, ISC Class 12 Biology

Lesson

Fertilisation and development

Part 3 — from the meeting of gametes to the birth and feeding of the baby.

In this lesson you will

Describe the physico-chemical events of fertilisation
Describe cleavage, blastocyst formation and implantation
State milestones of embryonic development and functions of the placenta
Explain the hormonal control of parturition and lactation

Concept

Physico-chemical events of fertilisation

Fertilisation is the fusion of a sperm with the ovum.

Concept

Sex of the baby

The ovum always carries an X chromosome. A sperm carries either X or Y (about half each). An X sperm gives a female (XX) zygote; a Y sperm gives a male (XY) zygote. So the father’s sperm decides the sex of the baby.

Table showing how the sperm determines the sex of the zygote
Sperm	Ovum	Zygote
X	X	XX: female
Y	X	XY: male

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