Darwinian Snails

Let’s start basic…

• Theory vs. Fact• “Accepted as truth” vs. “Proven to be true”• Ex) Gravitational Theory, Einstein's Relativity

Theorem, Atomic Theory

When did it all begin?

• History of Earth• When did life begin?• http://

www.youtube.com/watch?v=1t4sdgvy-pk

By the end of today…

Without your notes:• Define all bold terms• Relate each to a specific example that you’re

familiar with• Explain how Natural Selection gives rise to

Evolution• Exercise – Computer Model

Charles Darwin

• (1809 – 1882)

Charles Darwin

• Naturalist - Collected samples on the SS Beagle (almost 5 years)

• Found seashells in the top of mountains• Galapagos animals in isolation• Exotic species – peculiar behaviors• Dilemma with publishing his findings

Evolution

• How populations become different from each other

• New species evolve• Happens under infinite number of

circumstances• Some things we can’t explain but end up with

the same result

Evolution

• Many mechanisms for descent with modification

• Natural selection – genetic drift (bottleneck, founder effect)

• Mutations – very rare – NEVER serve to better the population – random

• Individuals/Species cannot produce genes desired to favor survival

Evolution

• Species evolve – NOT individuals (i.e.) Individuals DO NOT evolve, species evolve

• Individuals undergo physiological responses while species undergo adaptations

Evolution by natural selection

• Descent with modification• 3 Stipulations: Traits must be heritable, vary

within the population, and able to be selected for due to some fitness advantage

• Traits can evolve from predation – selective pressures

Just Physical Traits?..

• Social behaviors (can evolve just the same as genotypes)

• http://www.youtube.com/watch?v=UNka9369t6Y

How does a species/population NOT evolve?

• Infinitely large pop• Random mating

• No migration• No Mutation• No Natural Selection

Lab Example

• Flat periwinkle populations yield variable shell thickness

• Due to predation by European green crabs• 1.) If individuals can’t change, how can

populations possibly evolve?• 2.) Did the population acquire new traits from

a need to battle predation?..

Critical Thinking

• Why do mitochondria in your cells have a separate genome from the nucleus?

• How could global warming affect the increase in tropical disease rates? (Swine flu?; also killer bees, etc.)

References

• http://danassays.files.wordpress.com/2009/05/charles-darwin-31.jpg?w=844

• http://www.worldsocialism.org/spgb/feb09/images/C_Darwin.jpg

• http://www.eskom.co.za/nuclear_energy/fuel/atom.jpg