EVO 5 - Mechanisms of evolution: genetic drift and gene flow

Why is genetic variation advantageous in a population?

Genetic variation helps a population survive environmental changes by offering different traits that might be beneficial. If a new disease or condition hits, some individuals are more likely to have the right traits to survive.

What is genetic drift?

Genetic drift is a random change in allele frequencies in a population, especially in small populations. It can cause alleles to become more or less common purely by chance.

How does genetic drift affect small populations?

In small populations, genetic drift has a big impact because there are fewer individuals, making it more likely for alleles to disappear or become more common by chance.

What is gene flow?

Gene flow is the movement of alleles between populations, often due to migration. It introduces new genetic material into a population.

How can gene flow increase or decrease fitness?

Gene flow can increase fitness if the new alleles help the population adapt (e.g., disease resistance). It can decrease fitness if the new alleles are not beneficial (e.g., making the population less adaptable).

What's the difference between gene flow and genetic drift?

Gene flow is the movement of alleles between populations, while genetic drift is a random change in allele frequencies within a population, especially in small groups.

How do selection, genetic drift, and gene flow differ?

Selection is adaptive and favors traits that help survival. Genetic drift and gene flow are random events that don't necessarily improve survival, with drift being random changes and gene flow being the movement of alleles.

Why is natural selection fundamentally different from genetic drift and gene flow?

Natural selection is purposeful—it actively favors traits that improve survival. Drift and gene flow are random, and don’t target the best traits for survival.

What are the key characteristics of genetic drift?

Genetic drift is random, usually happens in small populations, and can cause alleles to be lost or become more common by chance, regardless of fitness.

What does gene flow do to a population's gene pool?

Gene flow increases diversity in the gene pool by introducing new alleles from other populations, mixing genetic material between groups.

What is the relationship between gene flow and population fitness?

Gene flow can increase fitness if new alleles are helpful, like resistance to disease. It can decrease fitness if the new alleles are harmful or less advantageous.

Why is it important to understand how genetic drift, gene flow, and selection affect evolution?

Understanding these processes lets us predict how populations change over time and how certain traits spread, helping explain the diversity of life.

What’s an example of genetic drift in action?

In a small population of frogs, if one frog with a rare trait (e.g., a specific color) doesn’t reproduce, that trait could disappear from the population due to drift, purely by chance.

What’s an example of gene flow?

A bird from one population migrates to another and mates, bringing new alleles (traits) into the second population, which changes the gene pool.

How does genetic drift differ from natural selection?

Genetic drift is random and doesn’t favor any specific trait, while natural selection actively favors traits that increase survival and reproduction.