Who Was Charles Darwin? - Theory of Evolution & Natural Selection

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  • 0:00 Charles Darwin and Evolution
  • 1:38 Evolution by Natural Selection
  • 5:42 Lesson Summary
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Lesson Transcript
Instructor: Angela Lynn Swafford

Lynn has a BS and MS in biology and has taught many college biology courses.

When you hear the name Charles Darwin, you probably think of evolution. However, Darwin did not come up with evolution. He explained a way for evolution to occur called natural selection. Learn more about Darwin and natural selection in this lesson.

Charles Darwin and Evolution

Charles Darwin was born in England in 1809. He enjoyed studying biology and geology, and in 1831, he got the opportunity to serve as a naturalist on a trip around the world on the H.M.S. Beagle. During this five year voyage, Darwin collected thousands of plants and animals from South America and the Galapagos Islands. He took lots of notes and made lots of observations about the organisms and landscapes he saw.

It is often thought that Charles Darwin came up with the theory of evolution, but this is not true. Evolution is change over time in populations, and this idea was around before Darwin. Darwin actually never even used the term evolution in his publications. Instead, he used descent with modification, which can be used interchangeably with evolution. One important thing to remember about evolution is that populations (groups of individuals of the same species) evolve, but individuals do not evolve.

Darwin's main contribution to science was that he explained a mechanism, or a way, for evolution to occur. This mechanism is called natural selection, which is a process in which individuals that are well suited to their environment will survive and reproduce better than other individuals. In 1859, Darwin published On the Origin of Species, in which he explained in detail his observations and theory of evolution by natural selection. The full title of this book is much more descriptive: On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life.

Theory of Evolution by Natural Selection

Let's examine natural selection in more detail. Darwin's theory of evolution by natural selection includes four important observations of nature:

  1. Members of a population of the same species vary in their traits.
  2. Traits can be inherited, or passed from parents to offspring.
  3. Populations are capable of producing more offspring than the environment can support.
  4. Due to a lack of food or other resources, many of the offspring do not survive.

Natural selection will only occur if all four of these observations are true for a population.

This is a population of moths. They are all the same species, but they vary. Some are brown, and some are gray. Color is a trait that can be inherited. In this example, brown moths produce brown offspring. Gray moths produce gray offspring. Each parent produces many offspring, but only a few of them will survive.

From his four observations, Darwin made two inferences to explain natural selection:

  1. Individuals whose inherited traits give them a higher chance of surviving and reproducing in their environment tend to leave more offspring than other individuals.
  2. This unequal ability of individuals to survive and reproduce, or differential survival and reproduction, will lead to the accumulation of favorable traits in the population over many generations.

Let us say that this moth population mostly lives on brown trees. This means that the brown moths will blend in and be hard for predators, like birds, to see. Gray moths stand out and will easily be eaten. So brown moths have a better chance of surviving than gray moths. Because the brown moths survive longer than the gray ones, they will have a better chance of reproducing. So over time, if only the brown moths reproduce, then the population will consist of only brown moths.

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