Variations in Populations – AP Biology College Board Revision

Understanding Variations in Populations

Variations refer to the differences between individuals within a population or species. These variations may be in their phenotypes (physical traits) or genotypes (genetic makeup).
Variations in a population arise primarily due to genetic differences, which can be caused by mutations, genetic recombination during sexual reproduction, or gene flow from other populations.
These variations are crucial for the survival of the population as they provide the raw material for natural selection. Individuals with variations that give them an advantage in their environment are more likely to survive and reproduce.

Genetic Variation: It is the diversity in genetic makeup among individuals within a population. It arises from mutations, gene swaps between chromosomes during meiosis, and gene flow.
Phenotypic Variation: It refers to the observable differences in physical and physiological traits among individuals in a population. It is determined by genetic factors and environmental influences.

Variations play a fundamental role in the process of natural selection. The variations making certain individuals better adapted to their environment enable them to survive and reproduce more successfully.
Over time, the frequency of these beneficial variations increases in the population, leading to evolutionary changes.
It’s important to note that natural selection doesn’t create variations; instead, it acts upon the existing variations in a population.

The different beak sizes and shapes in Darwin’s finches are an example of how variations within a population can lead to adaptation to specific food resources.
Similarly, the variations in the colour of peppered moths in 19th century England is another classic example.

Understanding variations in populations is critical for conservation strategies. Populations with more variations are likely to adapt better to environmental changes, making them less vulnerable to extinction.
In terms of human health, understanding genetic variation can help in predicting disease risks and devising personalised treatment strategies.
The concept is also essential in agriculture, aiding in the selection and breeding of desirable traits in crops or livestock.

It’s erroneous to assume that all variations in a population are subject to natural selection. Some variations may be neutral or even detrimental, providing no survival advantage.
Another misconception is that variations always lead to evolution. Variations can bring about evolutionary changes only when they result in differential survival and reproduction under specific environmental conditions.
Lastly, not all variations are genetic. Environmental factors can also cause variations, but these are not heritable and thus don’t contribute to evolution.