SEXUAL REPRODUCTION (PART-2)

 

STD-12      UNIT-6  CHA-1

REPRODUCTION IN ORGANISMS 

Event Of Sexual Reproduction 

• Gametogenesis
• Gamete transfer
• Fertilization 
• Embryogenesis(Formation of embryo )

Gametogenesis

IN ANIMALS 

- Spermatogenesis - formation of male gamete

- Oogenesis- formation of female gamete

IN PLANT 

- Microsporogenesis - formation of pollen grain

- Megasporogenesis - formation of megaspore

Gamete Transfer

IN BRYOPHYTES

Male gametes are motile Female gamete are nonmotile

In Algae bryophytes and pteridophytes of water serves as the medium throughout which gamete transfer take place

In flower bearing plants pollen grains carrying the male gametes are produced in large number, The pollen grains are transferred to the stigma of the female organ throughout the process of pollination

In animals have a copulatory organs to transfer the male gamete .

Transfer of gametes and coming together of gametes is essential for fertilization in sexual reproduction

Fertilization- 

 Fertilization is the fusion of gametes to form a diploid zygote

1) external fertilization - 

When fertilization occurs outside the body of the organism the gametic fusion is called as external fertilization e.g - FROG 

2) internal fertilization - 

That is fusion of gametes inside the body of the female - e.g- reptiles, birds & mammals

Embryogenesis - 

Formation of embryo 

On the basis of the development of the zygote animals are grouped

IN PLANT

IN ANIMAL 

OVIPAROUS- 

animals Lay fertilized or unfertilized eggs 

Reptiles ,Birds the fertilized eggs are covered by Hard calcareous shell and are laid in a safe place in the environment

After incubation period youngones hatch out

IN VIVIPAROUS  - 

animals such a majority of mammals including human beings zygote develops into a youngones inside the body of the female individual 

After certain growth the young ones are delivered by the female individual.

IN OVOVIVIPAROUS -

animals the female retains the eggs inside the body 

After fertilization and allows the development of the embryo inside the body without providing extra nourishment to the development of embryo as the pleasant is absent

However female animal give birth to their young ones 

example of oviparous animals are shark and rattle snakes

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MANISH MEVADA

M.Sc, M.Phil, B.Ed.

INDIA BIOLOGY NEET

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