In brief
Genetic recombination. During meiosis crossing over occurs and u get new combination of genes=>diversity 🙂

it’s for gametogenecys process.. to reduce the number of chromosom types from 2N (diploidi) into N (ploidi).. because male gamet and female gamet doing fertilitation process.. ovum with N type fuse with spermatozoon with N type, so the ovum become 2N type… and this ovum grows become an adult individual that consists of billion cells with mitocys, so every cell have 2N type of chromosom….

hope this is clear enough for u…
if something wrong with my explanation, please tell me.. ok?
thank’s a lot before…. 😀

i think there are mainly two importance:
1. reduction of chromosome number from diploid to haploid so that the resulatant chromosome number can be constant after the fertilisation process
2. random assortment of chromosome and crossing over give more genetic variation, or formation of new linkage groups that is favourable to the overall species such that the species can survive better on changing environment

varition…varition..variation…

Life would be boring if everyone are the same.

and probably extinct too 😉