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Question
Given below is the diagram of a human ovum surrounded by a few sperms. Study the diagram and answer the following questions :
(a) Which one of the sperms would reach the ovum earlier?
(b) Identify 'D' and 'E'. Mention the role of 'E'.
(c) Mention what helps the entry of sperm into the ovum and write the changes occurring in the ovum during the process.
(d) Name the specific region in the female reproductive system where the event represented in the diagram takes place.
Solution
(a) Sperm A will reach the ovum fastest.
(b) D - Cells of the corona radiata
E - Zona pellucida
The zona pellucida layers play several roles such as -
- it supports the communication between oocytes and follicle cells during oogenesis
- it protects the oocytes, eggs, and embryos during development
- it regulates interactions between ovulated eggs and free-swimming sperm during and following fertilization
(c) The anterior portion of the head of the sperm is covered by a cap-like structure called the acrosome. This acrosome is filled with enzymes that help in fertilization of the ovum. As a sperm comes in contact with the zona pellucida layer, it induces changes in the layer and blocks the entry of other sperms. The enzymes of the acrosome help the entry of the sperm into the cytoplasm of the ovum.
(d) This event of fertilization occurs in the ampullary region of the fallopian tube.
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RELATED QUESTIONS
Draw a diagrammatic sectional view of a mature anatropous ovule and label the following parts in it:
(i) that develops into seed coat.
(ii) that develops into an embryo after fertilization.
(iii) that develops into an endosperm in an albuminous seed.
(iv) through which the pollen tube gains entry into the embryo sac.
(v) that attaches the ovule to the placenta.
With a neat diagram explain the 7-celled, 8-nucleate nature of the female gametophyte.
Egg apparatus consists of ______.
Polygonum type of embryo sac/typical female gametophyte of angiosperms is ______.
Embryo sac is also known as ______.
Development of an organism from female gamete/egg without involving fertilization is ______.
Embryo sac occurs in ______.
Mature ovules are classified on the basis of funiculus. If micropyle comes to lie close to the funiculus the ovule is termed as ______.
Part of the gynoecium which receives the pollen is called ______.
In the figure of anatropous ovule given below, choose the correct option for the characteristic distribution of cells within the typical embryo sac
| Number of cells at the chalazal end | Number of cells at micropylar end | Number of nuclei left in the central cell | |
| A | 3 | 2 | 3 |
| B | 3 | 3 | 2 |
| C | 2 | 3 | 3 |
| D | 2 | 2 | 4 |
