Aim: What evidence do we have that Evolution took place?

I. Evolution – living things have changed from ancestors that they have in common.

A. Evidence of Evolution

1. Fossils – a fossil is any record of an organism that lived in the geologic past. Remains, impressions, and traces of organisms of past geologic ages have been preserved in the earth’s crust as fossils.

Question. Are all dead organisms preserved as fossils?

Answer: NO! Hard parts of organisms such as bones, teeth, and shells are more resistant to weathering. Also, dry environments help preserve fossils better.

a. Types of Fossils – animals can be created by refrigeration (wooly mammoth), imprints in soft mud, casts, insects trapped in amber, petrification. Coal is an example of fossilized plant remains. Tar pits(La Brea in Los Angeles).

b. Determining the Age of Fossils – older fossils are found at deeper layers of earth than younger ones, index fossils, and radioactive dating.

c. Evidences of Relationships - examination of rocks and fossils indicate that there was:• a change from simple to complex forms• change from marine to land forms• presence of intermediate forms• presence of transitional series• sufficient time for evolution to have occurred

Insect in Amber

Preserved bones

Imprints Casts

Link between reptiles and birds

Teeth

Bony Tail

2. Evidence from comparative cytology (the study of cells) - Most organisms are composed of cells, but even their organelles (tiny organs) are similar in structure and function.

3. Evidence from comparative biochemistry (the chemical reactions in living things) - The structure of DNA and RNA and the way they function is similar in all living things. Many different organisms have similar proteins and enzymes

4. Evidence from comparative anatomy

a. Analogous structures – have the same function but different evolutionary origins. Example: The wing of a fly and the wing of a bird. Fly wing is a membrane and the bird wing is bony covered with feathers.

b. Homologous structures – same basic structure and evolutionary origin. Example: human arm, wing of a bat, and the flipper of a whale.

Bird Wing

Insect wing

5. Evidence from immunologya. Similarities in blood proteins of various animals (ex: vaccines from horse)

6. Evidence from Embryology

a. Examine early stages of embryos and found great resemblance. See photo.b. These embryos then develop differently

as they grow.

What evidence do scientists have that evolution took place?