What Is Evolution? — Definition & Overview

What Is Evolution? How Does It Occur?

Evolution is the change in a population's gene pool over time. Small changes like DNA mutations coupled with natural selection lead to genetic diversity. This process takes many generations.

Remember that "theory" has a much different meaning in science than it does in everyday language. A scientific theory is an explanation that ties many different facts together. Theories are tested by experimentation over and over again. Evolutionary theory is supported by a variety of evidence. This ranges from fossils to biochemical data. Many of these theories stem from the research of Jean-Baptiste Lamarck and Charles Darwin. Darwin wrote about his observations in his book On the Origin of Species.

Relation to Natural Selection

Natural selection drives evolution. Small genetic variations and mutations can help, hurt, or not impact an organism. If it helps, the organism is more likely to reproduce and pass on its genes. If the change is unhelpful or limiting, the organism will have a harder time reproducing or even surviving. So, its genes are less likely to be passed on. When certain traits are chosen over others by potential mates, it is called sexual selection. Passing down genes from parent to offspring in this way is known as descent with modification and is part of Darwin's theory of evolution.

With this selection happening over a very long time, successive generations become well-equipped to deal with their environments. If a mutation is passed down and becomes part of the gene pool, it can alter the population's genetic makeup. When different populations of a species develop different adaptations, it can lead to speciation. For example, one population might adapt to be awake at night and another to be awake during the day. This means the two populations are temporally isolated and will stop mating. Eventually, they might become separate species.

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$\color{#8925AE}{\text{Evolution}}$ : The gene pool of a population changes over time

$\color{#8925AE}{\text{Natural Selection}}$ : Organisms with traits beneficial to their environment are more likely to survive and reproduce

(Video) Evolution: It's a Thing

by CrashCourse

Evolution is how populations change over time through mutation and adaptation. Major changes can take millions of years. In this video, Hank from Crash Course discusses the theory of evolution and how we know changes are happening. He explains evidence such as a universal genetic code, molecular biology, anatomical similarities, and vestigial body parts.

The Importance of Evolution

Understanding this topic is key to understanding how and why organisms look the way they do, act the way they do, and where all life on Earth came from. It's important to learn about not only human evolution and the human genome, but also how all organisms on our planet have changed over time. It's a big, important topic. Learning about the past and evolutionary history can help us learn about the present.