Final answer:
Gene flow and interbreeding prevent genetic isolation and speciation by increasing genetic diversity and reducing inbreeding depression.
Step-by-step explanation:
Gene flow and interbreeding act against genetic isolation and speciation. Gene flow involves the exchange of genetic material between populations, which introduces new alleles and increases genetic diversity. This process is essential for a species' adaptability and survival. When gene flow occurs through interbreeding, it reduces the likelihood of inbreeding depression, which can result from mating between close relatives in isolated populations. In contrast, prezygotic and postzygotic barriers prevent gene flow by inhibiting interbreeding between species, leading to genetic separation and the potential for new species to emerge over time.