What must happen in order for a new species to evolve?
1 Answer
Ultimate step to speciation is REPRODUCTIVE ISOLATION . Thus, in case of both sexually and asexually reproducing organisms, gene pool of new species must get separated from the gene pool of ancestral population .
Explanation:
A species population remains divided in subpopulations (= deme ). Members of subpopulations are able to interbreed among themselves. Interbreeding helps in exchanging genes (=gene flow) between subpopulations.
To take a definite step towards origin of new species, members of a subpopulation must become reproductively isolated from parental population. This may happen due to appearance of new mutations in the subpopulation or due to geographic isolation. This is why, subpopulation/deme is considered to be an evolutionary unit . Gene flow stops between new species and parental species as a virtual reproductive barrier separates them.
