Transcript Evidence for Evolution

Evidence for Evolution
What evidence do scientists have to support the
theory of evolution?
Similarities in DNA
By 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 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 Structure
Human 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 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 Vertebrates
Embryos 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! - 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 Record
Remains 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! - 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