Evidence for Evolution

What evidence do scientists have to support the theory of evolution?

Similarities in DNABy comparing the sequence of nitrogen bases in the DNA, scientists can infer how closely related species are.

Also recall that the DNA bases along a gene specify what type of protein will be produced. Thus, scientists can also compare the order of amino acids in a protein to see how closely related two species are.

THINK ACTIVITY!THINK ACTIVITY! - Think of 3 closely related species. Then, draw what the DNA sequences of these species may look like. Remember, there are 4 nitrogen bases in DNA.

Homologous Bone StructureHuman arms, cat forelegs, whale flippers, and bat wings all have the same basic combination of bones.

These are homologous structures. Homologous structures provide evidence that all mammals evolved from a common ancestor.

THINK ACTIVITYTHINK ACTIVITY! - Do you see the similarity in structure? Color the image showing similar bones in each structure.

Use a green, red, blue, yellow, & pink colored pencil to shade in the bones.

Embryos of VertebratesEmbryos of closely related organism often have similar stages in development. For example, all vertebrates have an embryonic stage in which:

• pouches appear on the side of the throat. • a tail develops• buds form which become limbs

This provides evidence that all vertebrates share a common ancestor.

THINK ACTIVITY!THINK ACTIVITY! - Take a look at the handout and analyze the embryos of different animals.

Analyze

1. Which two animals seem

to be the most closely

related?

2. How can you tell?

Fossil RecordRemains of organisms that lived in the past are called fossils. Most fossils are found in rocks.

Fossils can help link the past to the present.

Fossil evidence that supports that hypothesis that whales evolved from land dwelling ancestors who had 4 limbs. Baliosaurus is one of these early whales with hind limb bones.

THINK ACTIVITY!THINK ACTIVITY! - Whale evolution is extremely fascinating. Watch a video clip to learn more.

http://www.pbs.org/wgbh/evolution/library/03/4/l_034_05.html