1. Evolution
Evidence and Ideas

2. Evolution =
Change in populations over time

3. Fossil Evidence remains or traces of past life forms
most form from burial of plants & animals in sediment
soft parts are often consumed or decomposed but may leave imprints if buried rapidly

4. How do we know how old it is?
Relative dating is done by rock layers
(top layers of rock are the youngest)
Absolute dating uses radioactive isotopes (using half-lives and isotope amounts)

5. Extinction
death of all members of a species
Mass extinction = extinctions of many species in short time.
*There have been five mass extinctions so far and
many agree we are in the middle of one NOW

6. Mass Extinctions
Following extinctions, remaining groups expand to fill habitats vacated by extinct species.
Marine animal fossil record indicates mass extinctions occur every 26 million years--which corresponds to movement of our solar system within Milky Way galaxy.

7. Biogeographical Evidence
Biogeography is the study of the distribution of plants and animals throughout the world
Current organism distribution reflects evolutionary history
organisms evolve in one location and spread out into other regions
no rabbits are found in South America— they originated elsewhere and did not reach South America

8. Biogeographical Evidence
Physical factors limit population range (including location of continents)
Continental drift = continents have slowly moved over time
distribution of early reptiles across many continents from time when land was attached
divided distribution of mammals that evolved after continents parted

9. Anatomical Evidence Organisms have homologous structures:
vertebrate forelimbs contain same sets of bones for different functions

10. Anatomical Evidence
Simplest explanation is a common ancestor whose basic forelimb plan was modified in succeeding groups as each continued along its own evolutionary pathway

11. Anatomical Evidence
Homologous structures are similar structures derived through descent from a common ancestor but may have different functions. (leg, wing, fin)
Analogous structures have similar functions but differ in anatomy and did not derive from the same ancestral structure (insect wing and bird wing)

13. Anatomical Evidence Flightless birds have wings.
Vestigial structures are reduced and functionless anatomical features
Flightless birds have wings.
Snakes rear limb spurs.
Humans have a tail bone.

14. Anatomical Evidence
Related species share embryological development.

16. Biochemical Evidence
Almost all living organisms use the same basic biochemicals:
DNA, ATP, same enzymes, DNA triplet code, 20 amino acids…

17. Biochemical Evidence
Similarity of biochemistry is explained by descent from common ancestor.
Organisms show less difference in their DNA the more closely related they are:
2.5% difference between humans & chimpanzees
42% difference between humans & lemurs.

18. END OF DAY 1