Final answer:
Speciation is often caused by reproductive isolation and environmental changes, with ring speciation and sympatric speciation being two examples. Changes like isolation after a drop in water level can lead to a bottleneck effect and new species. When sympatrically speciated fish lose the ability to distinguish mates due to pollution, interbreeding might occur, reversing speciation.
Step-by-step explanation:
What Causes Speciation?
Speciation, the process by which new species form, can be driven by a variety of factors, often centered around reproductive isolation and environmental changes. One key example is ring speciation, as seen in California's genus Ensatina salamanders. In this phenomenon, populations of a species become geographically separated and adapt to their local environments over time, leading to reproductive isolation and the emergence of new species.
Another speciation process is sympatric speciation, where a population develops into new species within the same environment. This can be due to genetic mutations, such as polyploidy, or behavioral changes, such as a shift in diet or habitat use, causing a subset of the population to reproduce only among themselves.
Environmental changes, such as a water level drop that isolates a population of snails, can lead to a bottleneck effect where genetic variation is reduced. In such cases, any beneficial mutations are likely to become more common in the population, potentially leading to speciation.
In the scenario with fish undergoing sympatric speciation, if pollution clouds the water and prevents females from distinguishing males by color, there may be interbreeding between the species. This could lead to genetic mixing and potentially reduce distinctiveness between the species, thereby reversing the process of speciation.