OBJECTIVE 6 NOTESEvolution, Natural Selection & Adaptations

1. Vocaba) Evolution

• A genetic change in a population over time• Note: individuals do not evolve, only populations show change

b) Theory• A well supported explanation of a scientific phenomenon

c) Fitness• The ability of an organism to survive and reproduce in a given

environment

2. Charles Darwin• From 1831-1836, a young naturalist called

Charles Darwin toured the world in HMS Beagle.

• Where food was limited, competition meant that only the fittest would survive.

• This would lead to the natural selection of the best adapted individuals

3. Assumptions of the Evolutionary Theory

• The earth is billions of years old

• Time + small changes = large changes

• Mutations can be beneficial

3. Natural Selection• The process by which individuals that are better suited to

their environment survive and reproduce most successfully

• Also called:• Survival of the Fittest

• Artificial Selection

3. Natural Selection• Types

4. Mechanisms of Evolution • Genetic Variation

• Mutations• Meiosis (crossing over)

• Natural Selection• Reproductive Isolation

5. Evidence of Evolution• Fossil Records• Homologous Structures• Analogous Structures• Vestigial Structures• DNA

Fossil Record• Fossils are preserved evidence of dead organisms• Assumes that it takes a long time for sediment to

accumulate• Assumes that the dead organism had offspring• Assumes that there are millions of years separating each

sediment layer.

Homologous Structures• Structures that have a similar structure (anatomy) from one

organism to another.

• Example: limbs– Human leg v. Whale

flipper• Both contain bones

called femur, tibia, fibula, etc.

• Similar structure but different functions

Analagous Structures• Structures that have a similar function (physiology) but

different structure between organisms.

• Example: Wings• Butterfly wing v. Bird wing• Both enable flight, but are very different structures

Vestigial Structures• Defined as a structure that serves no useful function in an

organism.• Most common citations of this are not accurate:

• Coccycx: without it humans cannot pass solid waste.• Appendix: might have immune/lyphatic functions• Tonsils: have immune and lyphatic functions• Eyebrow/lash: keeps sweat/dust/particles out of eyes• Body Hair: mechanoreceptors at base, traps heat, offers protection

from sun rays