The Theory of Evolution Print Friendly and PDF

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Darwin's Theory of Evolution by Natural Selection

What is evolution?

Evolution is considered the "Unifying Theory" of biology because it helps us understand the diversity of life on the planet.

For example, why are lions and tigers so similar, but live on different continents.

What is a theory? - Statements of models that have been tested and confirmed.

Questions can be answered using established theories.

Example: Why do so many different animals have the same bone pattern in their limbs?

Homologous structures - similar body parts, but different functions

Predictions can be made using theories.

Example: Would a penguin lay eggs?
Answer: Penguins are birds, they lay eggs

Main Ideas of Evolution

*Frequency refers to the number of organisms that have a particular trait.

Evolution by Natural Selection

Darwin was a naturalist who observed many species.
He is famous for his trips to the Galapagos Islands, his observations of the finches (and other animals)
He wrote: "The Origin of Species"
His idea of natural selection is sometimes referred to as the "survival of the fittest."

Observations from the Galapagos


finchDarwin's Finches:

Darwin noted that all the finches on the galapagos island looked about the same except for the shape of their beak. His observations lead to the conclusion that all the finches were descendents of the same original population. The shape of the beaks were adaptations for eating a particular type of food (Ex. long beaks were used for eating insects, short for seeds)

Video on Galapagos Finch Evolution with Student Guide

Main Points from "The Origin of Species"

Use the VIDA Chart to explain evolution in model organisms

1. Variation exists among individuals in a species.
2. Individuals of species will compete for resources (food and space)
3. Differential survival and reproduction
4. Adaptation: Individuals that had advantageous variations are more likely to survive and reproduce.

Model Organisms

Tuskless Elephants in Africa
Lizards in the Bahamas
Anoles in the Caribbean
Artificial selection in domestic dogs

Next: What is the Evidence for Evolution?

Evolution Activities

Galapagos Finches (HHMI Video)

Evolution by Natural Selection (VIDA) Elephants
Evolution of Rabbits and Wolves (VIDA)

Rock Pocket Mouse HHMI Activity

Evolution Concept Map
Evolution Crossword