Genetic drift is an important part of how species change over time. It can cause big changes in the genes of small groups of animals or plants. Unlike natural selection, which is about survival of the fittest, genetic drift happens more by chance. It affects the frequency of different gene versions (called alleles) randomly, especially in smaller populations.

Important Points About Genetic Drift:

1. Random Sampling Effect:

   • In small groups, just a few individuals can have a big impact on the genes of the whole group.
   • For example, if there are only 10 animals in a population, losing or gaining just one can change the gene frequency by 10%. That’s a huge change compared to larger groups.

2. Bottleneck Effect:

   • Sometimes, a large number of individuals in a population can suddenly die off due to an event like a natural disaster.
   • This is called the bottleneck effect, and it can lead to a small group of survivors, which might not have all the original genetic diversity.
   • Imagine a population of 1,000 animals gets knocked down to just 50. The genes from these 50 might be very different from the original 1,000, reducing variety in the gene pool.

3. Founder Effect:

   • The founder effect happens when a new group starts from just a few individuals.
   • This can make certain genes very common in this new group.
   • For example, if only 5 animals move to a new area, their traits might become very common in that new population, no matter how common they were in their original group.

Some Statistics:

• Research shows that in small populations, genetic drift can lead to a loss of 1-2% of genetic variation (called heterozygosity) every generation. This is especially true if the populations are isolated.
• If a group has only about 30 individuals, there’s a pretty good chance—about 90%—that a gene will become very common (or fixed) within just 10 generations due to genetic drift.

Conclusion:

In summary, genetic drift can really change small populations quickly. It can lead to fewer different genes and can change the path of how species evolve over time.