AOA!And this one also..plz..
Explain the role of isolating mechanisms in the evolution of new species;
Species are evolved by allopatric as well as sypatric speciation. Isolating mechanisms play very imp. role in separation of different groups of species which may later on develop into new species. In allopatric speciation, geographical isolation occurs in which groups of species move to new places and separate by geographicsal barriers, i.e a mountain range or large forest etc.
Some organisms may move to a distant island surrounded by vast ocean around. In sympatric speciation (examples include evolution of wheat) when two parents from different species breed, the chromosomes are not the same, so meiosis becomes a problem. A hybrid species, if successful, is generally a polypoid with many sets of chromosomes. Many species are isolated by behavioral, temporal, ecological & structural isolation mechanisms. Isolated groups or populations cannot interbreed because their members cannot breed among themselves; hence no gene flow occurs and genes cannot mix b/w populations. Different selection pressures operate in specific environment,. Natural selection occurs and organisms with best adapted traits survive. It brings about change in allele frequencies and gene pool of population becomes different. Over a long period of time, such differences, due to isolating mechanisms, prevent interbreeding and species are reproductively isolated. Once reproductively isolated, the new species emerge are different from ancestral species.
A bit too long, I guess. But you can 'filter out' the best points.