7.12 Variations in Population

Skills you’ll gain in this topic:

• Explain how genetic variation within populations supports adaptation and survival.
• Describe the sources of genetic variation, including mutations and recombination.
• Analyze the importance of variation in response to environmental changes.
• Predict how low genetic diversity affects a population’s adaptability.
• Relate genetic diversity to a population's potential for long-term survival.

Genetic Diversity and Why Genetic Variation is Crucial for Survival

Genetic diversity in populations is very important. It helps increase a population's chances to be able to respond to changes in the environment. Populations with little genetic diversity are those that are at the highest risk of decline and extinction. 

Genetically diverse populations are more resilient to environmental impacts, as they are more likely to contain individuals with heritable genetic variations that predispose them to a higher likelihood of surviving and passing on their traits to offspring through reproduction. 🧬

Image courtesy of Giphy.

Population Survival

Having a variety of different traits within a population is advantageous for survival because selective pressures vary (usually linked to the state of the ecosystem/environment). A condition that was previously deemed “advantageous” could become harmful to a population under new environmental conditions. The allele would then, theoretically, be selected against, and the number of individuals carrying that gene would begin to decrease.

For example, let's say a population of birds is living in an area where the average temperature is gradually increasing over time. If the birds have a wide range of genetic variations that allow for the production of different types of feathers, some of them may have feathers that are better suited to insulate against higher temperatures. These birds will be more likely to survive and reproduce, passing on their beneficial traits to the next generation. As a result, the population will adapt to the changing environment and continue to thrive. 🦜

On the other hand, if the population has low genetic diversity and all of the birds have the same type of feathers, they may not be able to adapt to the changing temperatures as effectively. This could lead to a decline in their population size or even their extinction.

Genetic diversity even explains why it is difficult to deal with parasites and bacteria. Bacteria populations use genetic diversity to develop antibiotic resistance, just as insects, like mosquitoes, develop resistance to the pesticide protection of mosquito netting. No matter the species, genetic diversity is a critical component of the adaptation, survival, and resilience of species. 🦠

Essentially, alleles that are adaptive in one environmental condition may be deleterious in another. By having a large pool of genetic diversity, there is an increased likelihood that some individual in the population has adaptive traits that increase their fitness relative to fluid selective pressures. A diverse array of species with a wide range of genetic variations can help to ensure that the ecosystem is able to function properly and withstand various types of stressors or disturbances.

Check out the AP Bio Unit 7 Replays or watch the 2021 Unit 7 Cram