Chapter 3-Lesson 3 Notes

How Do New Species Evolve?

Charles Darwin

• Charles Darwin observed many unusual species of animals during a trip in 1835 through the Galapagos Islands.
• Darwin sailed on the HMS Beagle from 1831-1836
• Darwin noticed that similar species on different islands had adaptations that enabled them to survive in their different environments.

Example:

• Tortoises on different islands had shells of different shapes.  Their legs and necks of different lengths enabled them to find food or survive the environmental conditions on the various islands.

• Darwin also observed 13 different species of finches in the Galapogos  Islands.
• He noticed that the beaks of the finches on each island matched the available food.
• Through his research and observations, Darwin proposed the theory of natural selection.

Natural Selection is the idea that those organisms best adapted to their environment will be the ones most likely to survive. (Survival of the fittest!)

The main points of Darwin's theory are:

1. Organisms usually produce more offspring than can survive.
2. Competition exists among organisms. Those organisms that survive the competition are the only ones to reporduce and pass on their traits to offspring.
3. Organisms best adapted to their environments are the ones most likely to survivie long enough to reproduce.
4. Parent organisms pass traits on to their offspring.  Offspring usually look like their parents, but variations may occur.

Adaptations Over Time

• Certain traits may help an organism survive in its environment better than organisms that lack those traits.
• Long front teeth, claws, and sensative hairs are physical traits (structural adaptations) that help mole rats survive in their environment.

• A structural adaptation is an adaptation that involves body parts or color.
• Structural adaptations can take thousands or millions of years to evolve or they can evolve quickly.

New Species over Time

Populations are all the organisms of one species that live in a certain place.

• A population can become isolated when a barrier, such as a widened river, seperates some members of a population from others.
• Isolation can also occur when groups of animals migrate and become permanently seperated.
• When a population becomes isolated, each population adapts to its environment through natural selection.
• Successful traits are passed on to future generations.