Final answer:
Continental drift is the gradual movement of the Earth's continents over time, which has affected the dispersal of organisms and can explain why unique species are often found on islands.
Step-by-step explanation:
Continental drift is the gradual movement of the Earth's continents over time. It is caused by the movement of tectonic plates beneath the Earth's surface. This movement has had a significant impact on the dispersal of organisms.
Continental drift has affected the dispersal of organisms by creating barriers and land bridges, impacting migration routes and gene flow between populations. For example, when land bridges formed between continents, species were able to disperse across previously isolated regions. On the other hand, when continents drifted apart, species became separated and evolved independently.
Continental drift can explain why unique species are often found on islands. As continents separate and move, some landmasses become isolated, forming islands. These isolated environments offer unique ecological niches that lead to the evolution of distinct species found only on those islands. This process is known as adaptive radiation.