Charles Darwin’s theory of evolution is one of the most famous scientific theories in history. It describes how species change over time through the process of natural selection. Darwin’s theory is based on several key observations and ideas, which we will explore in this article.

Observation 1: Variation Exists Within Populations

The first key observation that Darwin made was that there is variation within populations of organisms. This means that individuals within a population have different traits, such as different sizes, shapes, colors, or behaviors.

Observation 2: More Offspring are Produced Than Can Survive

The second observation was that more offspring are produced than can survive. This means that there is competition for resources like food, water, and shelter. Only those individuals with traits that give them an advantage in this competition will survive and reproduce.

Idea 1: Natural Selection

Darwin’s big idea was natural selection. He realized that the individuals with advantageous traits would be more likely to survive and reproduce, passing on their advantageous traits to their offspring. Over time, these advantageous traits would become more common in the population because they give an advantage in the competition for resources.


For example, imagine a population of birds where some have long beaks and others have short beaks. If the environment has lots of insects to eat and only deep crevices for birds with long beaks to reach them then birds with longer beaks will have an advantage over those with shorter beaks as they can easily access food. So eventually birds with longer beaks will become common in this population.

Idea 2: Descent with Modification

Another important idea in Darwin’s theory is descent with modification. This means that all living things share a common ancestor but have changed over time as they adapted to different environments. This is why we see so much variation in living things today.


For example, humans and chimpanzees share a common ancestor, but over time, they evolved differently to fit different niches and environments. Humans have evolved to walk on two legs and have larger brains, while chimpanzees still walk on all fours and have smaller brains.

The Importance of Darwin’s Theory

Darwin’s theory of evolution is important because it explains how species change over time and how new species can arise. It also helps us understand the diversity of life on Earth and why some species are better suited to certain environments than others.


In conclusion, Darwin’s theory of evolution is a fundamental concept in biology. It describes how variation within populations, competition for resources, natural selection, and descent with modification work together to shape the diversity of life on Earth.