Question

natural selection and speciation leads to evolution justify it

Answer 1

Within a gene pool of a population, there is genetic variation, due to mutation. This leads to phenotypic variation. Some individuals will be better adapted to the environment than others and will therefore be more likely to breed and pass on their alleles to the next generation. This means that each generation will be slightly better adapted to the environment than the last, and thus evolution occurs. If a population is divided, and each fragment is isolated from each other (for example a river separating them, or continental drift), then they cannot interbreed. Each new populaion will face a different environment and therefore different selection pressures. This means that each population will begin to evolve different adaptations to suit their environment, and will eventually be so physically and genetically different that they can't breed and produce live, fertile offspring. This means that the two populations are now two seperate species, and speciation has occured. If they are reintroduced to each other (the isolating feature is lost), they will not interbreed.

Answer 2

Answer:

Reproductive isolation takes place when the given group of species are not allowed to mate with each other due to physical barrier, and speciation is said to occur when a single species divide into group and become a two or more separate species, which can no longer interbreed with each other.

Reproductive isolation is required for speciation to occur because if it do not occur the member of the same species continue to interbreed with each other, and because of this mating there are chances that any beneficial mutation may occur, which will cause evolution in the population.