The theory of evolution by natural selection is one of the most important scientific theories in the world. It explains how species change over time, and why some traits become more common in a population while others disappear.

But what exactly is being selected in this process? Let’s explore.

The Basics of Natural Selection

Natural selection is a process that occurs when certain traits give an organism an advantage in its environment. For example, a bird with a longer beak may be better able to reach food than a bird with a shorter beak. Over time, the birds with longer beaks will have more offspring than those with shorter beaks, and the average length of the beaks in the population will increase.

This process is driven by three key factors: variation, heritability, and differential reproductive success. Variation refers to differences between individuals within a population; heritability means that some of these differences are passed down from parents to offspring; and differential reproductive success means that some individuals have more offspring than others.

What Is Being Selected?

So what exactly is being selected in natural selection? The answer is simple: traits. More specifically, it’s the genes that control those traits.

For example, let’s say there are two types of beetles: green and brown. Birds prefer to eat green beetles because they are easier to spot against their brown environment.

Over time, the brown beetles become more common because they are less likely to be eaten. This happens because the gene for brown coloration becomes more common as brown beetles have more offspring than green beetles.

In this case, it’s not just the color that’s being selected – it’s the gene for that color. This gene controls whether an individual beetle will be green or brown, and it’s passed down from parents to offspring through reproduction.

There are different types of natural selection, depending on the specific pressures in the environment. One type is called directional selection, which occurs when one extreme of a trait is favored over the other. For example, if birds start to prefer smaller beetles instead of larger ones, the gene for smaller size would become more common in the population.


In conclusion, natural selection is a process that selects for certain traits in a population. These traits are controlled by genes, which are passed down from parents to offspring.

Understanding what’s being selected is crucial to understanding how evolution works and how species change over time. By studying natural selection, scientists can gain insights into the diversity of life on our planet and how it came to be.