Biology Class 12 NCERT Solutions: Chapter 3 Human Reproduction Part 4

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Q.12 What is oogenesis? Give a brief account of oogenesis.

Answer:

  • Oogenesis is the process of the formation of a mature ovum from the oogonia in females. It takes place in the ovaries.

  • During oogenesis, a diploid oogonium or egg mother cell increases in size and gets transformed into a diploid primary oocyte.

  • This diploid primary oocyte undergoes first meiotic division i.e., meiosis I or reductional division to form two unequal haploid cells.

  • The smaller cell is known as the first polar body, while the larger cell is known as the secondary oocyte.

  • This secondary oocyte undergoes second meiotic division i.e., meiosis II or equational division and gives rise to a second polar body and an ovum.

  • Hence, in the process of oogenesis, a diploid oogonium produces a single haploid ovum while two or three polar bodies are produced.

Image of Process of Oogenesis

Image of Process of Oogenesis

Q.13 Draw a labeled diagram of a section through ovary.

Answer:

Image of Normal Ovary

Image of Normal Ovary

Q.14 Draw a labeled diagram of a Graafian Follicle?

Answer:

Image of Graafian Follicle

Image of Graafian Follicle

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