REPRODUCTION (ASEXUAL)

Reproduction is a process by which all living organisms give rise to new individuals which are very much similar to their parents.

ASEXUAL REPRODUCTION

1.   In this only one parent is involved

2.   No gametes are involved

3.     In this process, the off springs are identical to their parent.

4.    It occurs in lower classes of organisms. For example amoeba, plasmodium, planaria etc.

TYPES OF ASEXUAL REPRODUCTION

BINARY FISSION

This occurs in amoeba. At first, the nucleus divides itself into two separate nuclei. Then a constriction is formed in the cytoplasm. The constriction begins to deepen resulting in the formation of two daughter amoebas which have their own cell apparatus which is identical to their parent. It can occur in any plane in amoeba but in leishmania it can only happen in longitudinal plane due to the presence of flagella on one end.

MULTIPLE FISSION

This occurs in plasmodium (the malarial parasite). In this process, the living organisms divide themselves into many daughter cells which are identical to their parent.

BUDDING

This takes place in yeast. Yeast gives rise to two unequal daughter cells. The smaller bud appears on the parent yeast and a long chain is produced which separates to grow further.

FRAGMENTATION

In this process the living organism divides itself into smaller fragments which then grow into new individuals. For example: spirogyra. Unlike regeneration no specialized cells are involved in fragmentation. For example: spirogyra.

REGENERATION 

This is another mode of reproduction in which the organisms have the ability to regenerate the lost body parts. Surprisingly, even if it is cut into 1/6th mm parts of its body it is able to regenerate and form a new individual. 

REGENERATION vs. FRAGMENTATION

Now, students often get confused between regeneration and fragmentation  so here you go

1. in regeneration specialized cells are involved. These cells revive and differentiate to form tissues, tissues forms organs and organs form the .....individual (ta-dah) Since it is performed in highly orderly manner this process is called development (lame right?)while no such procedure is followed in fragmentation. 

2.  In fragmentation, the fragments formed grow into an individual but in regeneration the lost parts may/may not form into a new individual. for example: lizard. the tail it drops i mean shed off does not regenerate to become a new lizard! (thank god the idea in itself is horrible!)

3. GIVE EXAMPLES!

4. DEFINATION (i know it should have been the first ): )

SPORE FORMATION

It occurs in fungi. I personally think it is most interesting of all asexual reproduction method ! So in this method the spores drifting in the air falls on suitable substratum like bread (i wanted to sound cool okay?) when it falls it germinates to form a white cottony thread like structure called hyphae. the nutrients and misture is taken by the roots who emerge from hyphae called rhizoids. the vertical hyphae are called sporangiophore which have sporangium on their tips.(so spore-ish) the sporangium contains spores and when it bursts it various spores pack their bags coolly saying adios to their parent in search of suitable substratum (-.-' i know) the spore have thick walls which protects them against adverse environmental condition.