Final answer:
A sufficient immigration rate is necessary to maintain genetic variation in organisms and populations. Immigration introduces new alleles, preventing genetic drift and promoting genetic diversity. This genetic variation allows populations to adapt to environmental changes.
Step-by-step explanation:
In order to maintain genetic variation for most organisms and populations, a sufficient immigration rate is needed. Immigration of new individuals can introduce new alleles into a population, preventing genetic drift and promoting genetic diversity. When a population receives a consistent source of immigrant individuals with specific alleles, those alleles have a higher chance of increasing in frequency within the population. This immigration-driven genetic variation allows populations to adapt and survive changing environmental conditions.