EvolutionBasics and Evidence

First, a Few Terms• Species A group of the same type of

organism that can interbreed and produce fertile offspring (humans are a species, homo sapiens)

• Population Group of the same species in a specific area

Evolution. What is it?

• Small or large genetic change at a population level inherited over several generations.

• Has to occur at the genetic level– Changes in allele frequency in a population over time

changes due to mutation and are passed along• Changes are seen in phenotypes (physical traits)• Descent with modification• Suggests common ancestor

EVIDENCE OF EVOLUTION

Anatomical Structures

Homologous Structures• If a bat, a human, an alligator, and a penguin

all evolved from a common ancestor, then they should share common anatomical traits

Vestigial Structures

• Body parts that seaming have no function• At one time in evolutionary history, they were

needed– Such as the pelvis of a whale, pelvic girdle in some

snakes, wisdom teeth• Leftovers from evolution• It used to be thought our appendix was vestigial,

however, it is thought that when beneficial bacteria in our gut is depleted, the appendix allows them to be re stored;

Biochemical (Molecular) Evidence

• Organisms that are more related have fewer differences in their amino acid sequences. (Cytochrome C below)

Fossils

• Fossils– Formed when organism dies is in silt, mud, sand or

clay soon after death– Sometimes an insect will die in tree sap (amber)

• Not all dead organisms will fossilize– The conditions have to be right!!

Example – Evolution of the Camel

Dinosaur National Monument: Fossilized dinosaur skeleton in sandstone

25.0 Fossil of a fish: perch

Dinosaur tracks (‘trace fossils’)

Barosaurus (27 m tall herbivore from late Jurassic (140 mya)

Leaf impression:Some fossils are imprints, some actually retain original organic matter

Petrified trees: Minerals dissolved in water seep into tissues of dead organisms, replace its organic material, and turn it to stone

Scorpion in hardened resin from a tree (whole organism preserved