1) Why Organism Have Sex?

 

It provides a way for organisms to swap and shuffle genes and to create offspring with new gene combinations that might survive if the environment suddenly changes.

 

Natural Cleansing

The new work could help test a hypothesis first proposed nearly 20 years ago, stating that sex evolved as a way to purge harmful mutations from a population. According to this view, the random shuffling of genes through sex will sometimes have the effect of concentrating many harmful mutations into single individuals.

 

These individuals will be less healthy than their peers, and therefore more likely to be weeded out by natural selection, the thinking goes.

 

By shuffling genes, sex allows a population to spread its mutations across many individuals within a group. The mutations become diluted and can be effectively dealt with by an individual's genetic repair system.

 

Evolution : http://en.wikipedia.org/wiki/Evolution_of_sex