What is Evolution?

It’s a gradual change in a species over time.

Background History:

Charles Darwin:

Explorer on a observation trip aboard the HMS Beagle in the Galapagos Islands.

He found a variety of species similar to those found in South and Central America and some completely new.

Darwin came up with the theory of Natural Selection

Natural Selection: means that organisms with traits best suited to their environment are more likely to survive and reproduce.

“Survival of the Fittest”

1.Organisms produce more offspring than can survive.

2. Variations are found among individuals of a species.

3. Variations are passed on to offspring.

4. Some variations allow members of a population to survive and reproduce better than others.

Over time, offspring of individuals with helpful variations make up more and more of a population.

Variations: an inherited trait (change in the DNA) that makes an individual different from other members of the same species.

Could be color, shape, behavior or chemical makeup

Evolution can happen in two ways:

1.Gradualism - a slow steady process where you can see different forms of the new species. Minor changes happen

Example: horse

2.Punctuated Equilibrium - happens quickly . Sometimes intermediate species are not there.

• Species branch off and evolve simultaneously.

Example: elephants

Branching Diagram Essential Questions:

1.Give a brief description of the evolutionary changes that occurred in the organism.

2.During which time period did the fossils differentiate into two branches? How did you know to branch off?

3.Explain how the chart illustrates both punctuated equilibrium and gradualism.

1. Fossil Record

Oldest fossils are at the bottom

Newest at the top

2. Homologous Structures - body parts that have the same number of bones, muscles or blood vessels.

3. Vestigial Structures - a body part that doesn’t seem to have a function at this time.

Example

Pelvic bone in whales

4. Embryology- studying organisms at the very early stages of development to see how they are the same.

Show overhead

5. DNA - Organisms that have close relatives have similar DNA. Example: dogs are the closest relative to bears.