Final answer:
When a population becomes isolated into two, it leads to habitat isolation and potentially allopatric speciation, as each group evolves independently and may result in reproductive isolation. Factors like natural selection, mutations, genetic drift, and specific genetic disorders can influence these changes within each isolated population.
Step-by-step explanation:
Effects of Population Isolation
When a population is isolated into two different populations, a process known as habitat isolation occurs. This leads to allopatric speciation, where the separate populations evolve independently due to factors such as natural selection, mutation, and genetic drift. As an example, if a cricket population is divided by a flood, they become reproductively and genetically independent. Over time, if two isolated populations experience different environmental pressures, they will likely accumulate distinct genetic changes, potentially becoming different species.
Reproductive isolation is an outcome of long-term separation, where differences in genetics and behavior reduce the likelihood of interbreeding if the populations are reunited. If isolated populations are brought together and cannot produce viable, fertile offspring, they are considered separate species. This isolation can also lead to increased frequency of certain genetic disorders within populations, as seen with Tay-Sachs disease in highly endogamous groups.
Different mechanisms like geological changes, the inability to return to the original habitat, or even cultural practices can lead to population isolation. For example, flying insects may continue to interbreed despite being in different valleys due to their ability to fly, while rodent populations separated by a lake may not, increasing the chances of speciation occurring.