Dr Pusey

www.puseyscience.com

Before we begin:

You may not agree with evolution, possibly for religious reasons.

This is a science class. Evolution is science.

Put on a brave face, and try to learn something anyway.

Recap - Mutation Mutation is a change to DNA which creates variation

This can be caused by environmental factors such as radiation, or simply be a mistake.

Mutation creates Variation Mutation is a change to DNA which creates variation

This can be caused by radiation, or simply be a mistake.

With each new generation, there is further variation. When variation favourable for reproduction (e.g. opposable thumb) appears, it will typically emerge in future generations.

How much variation is there until we call it a new species?

SpeciesDefinition: A group of similar individuals

capable of interbreeding and producing fertile offspring

Horse – 64 ChromosomesFertile

Donkey – 62 ChromosomesFertile

Mule – 63 ChromosomesInfertile (Mostly)

Crash Course - Speciation

Drivers of Variation Selection Pressure: Environmental factors

BIOTIC: Biological - e.g. other animals

If a certain gene makes it difficult to process pork, and you’re surrounded by nothing but pork, this variation won’t survive.

ABIOTIC: Not Biological – e.g. temperature

If a certain gene makes it difficult to deal with high temperatures, you won’t find these species in the desert.

These pressures are driven by change with location, and progressive change in our global environment (OMG CLIMATE CHANGE!)

Isolation If Jimmy the sheep has a gene mutation that makes his

wool pink, and it’s a dominant pink allele, how long until all the sheep in future generations get pink wool?

Depends on: Is pink wool attractive for mating?

Is Jimmy the only sheep available for mating?

What if Jimmy was on an Island? Would the pink allele make its way to other parts of the globe? Probably not.

This is called Isolation – Prevents allele flow

Natural Selection Variation in species drives natural selection

Alleles which are favourable in their environment (and good for reproduction) will prosper. Others will not.

“Survival of the fittest”

It’s more about having a selective advantage.

Consider an allele that makes a thin cave man who can’t deal with cold weather but can do calculations and debate VS a buff hairy caveman who can defend himself against mammoths but can’t count or talk. Which is more likely to reproduce during an Ice Age? What about these days?

Crash Course – Natural Selection

Evolution Changes in selective pressure will drive the change in

alleles (genetic traits).

Over time, a species may change dramatically, and in some cases form a new species.

Examples:

Peppered moth

Antibiotic resistance in bacteria

Darwin’s Finches

Stated Clearly - Evolution

Evidence for Evolution Fossils increase in complexity and diversity with age

DNA comparisons show genetic relationships

Comparison of homologous structures (hand/wing bones) between different species.

http://itc.gsw.edu/faculty/bcarter/histgeol/paleo2/homol1.htm

Stated Clearly – Evidence for Evolution