Question

what are the different events takes place in the process of sexual reproduction of an angiospermic plants?Describe briefly all the events with all necessary diagrams.

Answer 1

The events are: 1. Pre-Fertilization Events 2. Fertilisation 3. Post-Fertilisation Events.

1. Pre-Fertilization Events:

All the events of sexual reproduction that take place before the fusion of gametes are included in this category. Two main pre-fertilisation events are gametogenesis (formation of gametes) and gamete transfer.

(i) Gametogenesis:

The process of formation of male and female gametes is called gametogenesis. Gametes are haploid cells. Organisms such as monerans, fungi, algae and bryophytes have haploid parental body. Such type of organisms produce gametes by mitotic division and if the parent body is diploid; gametes are formed by meiosis.

When male and female gametes are similar appearance and it is not possible to differentiate them into male and female gametes, they are called homogametic or isogametes. If the male and female gametes are morphologically dissimilar they are called heterogametes. Among heterogametes, the male reproductive unit is called antherozoid or sperm and female reproductive unit is known as egg or ovum

2. Fertilisation:

The process of fusion of male gametes with the female gametes is called fertilisation or syngamy. It results in the formation of a diploid zygote.

It is mainly of two types:

i) External Fertilisation:

In majority of the aquatic organisms, e.g., algae, fish and in amphibians, the process of fertilisation takes place outside the body of the organism, i.e., in the water. This type of gametic fusion is called external fertilisation. To enhance the chances of fertilisation, the organisms exhibiting external fertilisation discharge a large number of gametes into the water, e.g., bony fishes, amphibians, etc.

(ii) Internal Fertilisation:

In most of the terrestrial organisms, e.g., fungi, higher animals and majority of plants such as bryophytes, pteridophytes, gymnosperms and angiosperms, the process of fertilisation takes place inside the body of the organism. This type of gametic fusion is called internal fertilisation.

3. Post-Fertilisation Events:

During the sexual reproduction, the events which take place after the formation of zygote are called post-fertilisation events.

(i) Zygote:

Fertilisation leads to the formation of a diploid cell called zygote. It is the vital link that ensures the continuity of species between the organisms of one generation and of the next.

Development of zygote depends on:

(a) Type of life cycle of the organism.

(b) Environment it is exposed.

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Answer 2

I felt so lazy to type

that's why photos

hope this helps you...