Reproductive isolation is a process of evolution that ensures that members of different species are incapable of mating and when they do, such mating do not result into any offspring or leads to the production of invalid offspring.
There are two mechanisms of reproductive isolation:
Pre-zygotic mechanisms prevents fertilization between two different species and these include habitat isolation, mating seasons, mechanical isolation, gamete isolation, geographical isolation and behavioral isolation.
Post-zygotic isolation prevents the products of fertilization from becoming valid and this include hybrid inviability, hybrid sterility and hybrid breakdown.
<em>Geographical isolation involves the existence of geographical barriers between two populations such that there cannot be mating between the two. The two populations eventually evolve to become different species.</em>
There is an outer core and an inner core. The outer core is extremely hot and is made mostly of molten (or melted) iron, which is called magma. It is about 1300 miles thick
