Class 10 | Science 2 | Easy notes on chapter 3 Life Processes in Living Organisms Part - 2

Class 10 | Science 2 | Easy notes on chapter 3 Life Processes in Living Organisms Part - 2

Reproduction : Formation of new organism of same species by earlier existing organism is called as reproduction.

Methods of reproduction :

1. Asexual reproduction 

2. Sexual reproduction

1. Asexual reproduction :

Process of formation of new organism by an organism of same species without

involvement of gametes is called as asexual reproduction.

• The new organism produced has genetically similar with the reproducing organism as no different gametes are involved. 

• This is uniparental reproduction

• It occurs by mitotic cell division.

• It is Fast process.

• Asexual reproduction of unicellular organisms :

There are three methods of asexual reproduction in unicellular organisms.

a. Binary fission

b. Multiple fission

c. Budding

a. Binary fission

• When one parent cell divides to form 2 similar daughter cells, it is called as binary fission.

• It is usually perform in favorable conditions.

• It occurs either by mitosis or amitosis.

• There are 3 types depending on how the cell divides.

i. Simple binary fission

ii. Transverse binary fission

iii. Longitudinal binary fission

i. Simple binary fission :

The cell divides in any plane due to lack of specific shape.

For example, amoeba

ii. Transverse binary fission : The cell divides horizontally.

For example, Paramecium

iii. Longitudinal binary fission : The cell divides vertically.

For example, Euglena

b. Multiple fission :

• When one cell divides into multiple daughter cells, it is called as multiple fission.

• It is performed by Amoeba and other similar protists.

• In unfavourable conditions,  amoeba stops formation of pseudopodia and thereby movements.

• Pseudopodia becomes rounded and forms protective covering around plasma membrane. Such encysted amoeba is called as ‘Cyst’.

• Then due to repeated nuclear divisions followed by

cytoplasmic division many amoebulae are formed in the cysts.

• When conditions becomes favourable, cyst breaks and

many amoebulae are released.

c. Budding :

• Asexual reproduction occurs by budding in yeast- a unicellular fungus.

• Yeast cell produces two daughter nuclei by mitotic division, so as to reproduce by budding.

• A small bulge (bud) appears on the surface of parent cell.

• One of the two daughter nuclei enters this bud.

• After sufficient growth, bud separates from the parent cell and starts to live independently as a daughter yeast cell.