Could someone answer this question-Targeted for Biology students?

Explain how natural selection could result in two poulations becoming separate species. (In regards to two species of salmon living in different areas of the sea with different breeding patterns)

Is it that over time, there would be a lot of competition between the same species of salmon and that inbreeding between small groups of salmon, meant that allele frequency decreased and the salmon developed a different niche. Also there may have been mutations expressed that were inherited from the ancestral population and that these could have resulted in different anatomical and behaviourial adaptations. With inbreeding of salmon, this would lead to homozygosity and reduce genetic diversity so that the salmon become specialised.

Anything else?

the main reason speciation occurs is due to genetic drift as a result of selection pressures

no no no.

genetic drift is not a result of selection pressure, thats the whole point.

natural selection and genetic drift lead to changes in allele frequencies which cause differences between populations. the differences are maintained due to reduced gene flow between them.

bad boy.

what's genetic drift then?
arghhhhhhhh!

Yeh pretty much but the main reason speciation occurs is due to genetic drift as a result of selection pressures. Some salmon may undergo allopatric speciation where the geographically different area may have different selection pressures i.e. a different predator. The salmon which have for example a phenotype or allele that improves the chances of survival are more likely to survive to reproduce hence the original alleles/phenotype drop in frequency as other alleles take precedent. As a result, the advantaged salmon breed at a greater rate than the original salmon. This then occurs for various selection pressures until eventually the salmon is so physiologically different to the original species that it can no longer freely interbreed with it to produce viable offspring.