The theory of evolution is one of the most fascinating scientific concepts to ever exist. It explains how life on earth has evolved over millions of years and how all living organisms are related to each other.

The principle theory of how evolution works is the theory of natural selection. Let’s explore this theory in detail.

What is natural selection?

Natural selection is a process by which organisms that are better adapted to their environment tend to survive and produce more offspring than those that are less adapted. This process results in changes in the characteristics of a population over time, leading to evolution.

How does natural selection work?

Natural selection works through three main principles: variation, inheritance, and differential survival and reproduction.


All organisms within a population exhibit variation in their traits or characteristics. This variation can be genetic or environmental. For example, some individuals may have genes that make them taller, while others may have genes that make them shorter.


Traits are passed down from parents to offspring through genetic inheritance. Offspring inherit a combination of genes from both parents, which can result in new variations.

Differential survival and reproduction

Not all individuals within a population will survive long enough to reproduce. Those that do survive will have different levels of success when it comes to reproducing and passing on their genes to the next generation. The individuals with traits that are better suited for their environment will have higher chances of survival and reproduction compared to those with less favorable traits.

Examples of natural selection

One classic example of natural selection is the case of peppered moths during the Industrial Revolution in England. Before the industrial revolution, most peppered moths had light-colored wings which helped them blend into tree bark where they rested during the day.

However, as factories began producing large amounts of soot, the tree bark became darker, making the light-colored moths more visible to predators. Over time, a new variant of the peppered moth with darker wings emerged and became more prevalent in the population.

Another example is antibiotic resistance in bacteria. When antibiotics are used to treat bacterial infections, only the bacteria with genes that make them resistant to the antibiotics will survive and reproduce. Over time, this can lead to an increase in antibiotic-resistant bacteria.


The theory of natural selection is the principle theory of how evolution works. It explains how organisms adapt to their environment over time through a process of variation, inheritance, and differential survival and reproduction. By understanding this process, we can better appreciate the incredible diversity of life on earth and how it has come to be.