Theory of Natural Selection

Charles Darwin (1809-1882)

HMS Beagle

The 5-Year Journey

Galapagos Islands

Darwin’s Finches

Galapagos Island Fauna

Galapagos Tortoise

Marine Iguana

Galapagos Island Fauna

Blue-footed BoobyGalapagos Sea Lion

Theory of Natural Selection

Consists of 5 main ideas:

1. Variation that is inheritable.

2. Overproduction

3. Struggle for existence

4. Survival of the fittest

5. Origin of new species by inheritance of successful variations

1. Variation

• Individuals within a species are not identical; they have variations.

• These variations may affect the individual’s ability to get food, escape predators, find a mate, etc.

• These variations can be passed on to offspring.

2. Overproduction

• Most species produce far more offspring than are needed to maintain the population.

3. Struggle for Existence

• Living space and food is limited and so individuals within a species must compete with each other in order to live long enough to reproduce.

4. Survival of the Fittest

• The individuals with traits that give them an advantage are better able to compete, survive, and reproduce, thus passing their “successful” genes onto their offspring.

• Nature “selects” the creatures that are best adapted to their environment.

5. Origin of New Species

• Over many generations, favorable adaptations gradually accumulate in the species and unfavorable ones disappear.

• Eventually the changes become so great that the end result is a new species.