UNIT 6 SEMINAR Evolution and Natural Selection

Agenda  What is evolution?  What drives evolutionary change?  What is natural selection?  What role do new mutations play in this process?  Video: The Evolution of Homer Simpson  Evolution resource: “Evolution 101” from UC Berkeley

What is evolution?  Evolution =

What is evolution?  Evolution = the change in inherited traits present in a population over time.

What is evolution?  Evolution = the change in inherited traits present in a population over time.  Present day species evolved from earlier species

What is evolution?  Evolution = the change in inherited traits present in a population over time.  Present day species evolved from earlier species  The relatedness of organisms is a result of common ancestry

What is evolution?  Evolution depends on understanding a few concepts:  Inheritance – genetic traits are passed from parents to offspring  Variation – there is genetic variety within a population (polymorphism)  Time – major evolutionary changes happen over hundreds or thousands of generations.

What drives evolutionary change?  Mechanisms of evolution include:  Natural selection  New mutations  Genetic drift (small populations)  Gene flow (migration)  Hybridization

What is natural selection?  Natural selection =

What is natural selection?  Natural selection = process by which certain traits become more or less common depending on their effects on the “fitness” of individuals  Fitness =

What is natural selection?  Natural selection = process by which certain traits become more or less common depending on their effects on the “fitness” of individuals  Fitness = ability to reproduce and contribute to the gene pool. VS

Artificial Selection

“Survival of the Fittest”  What are some factors that could affect the “fittness” of an individual?

Natural selection: Example  Imagine a population of beetles in which there are both green and brown varieties.  If birds prefer to eat the green ones, then the brown ones have an advantage and will reproduce more.

Natural Selection: Example

Role of Mutations in Evolution  Sometimes, a new mutation confers a selective advantage in an individual, resulting in increased reproduction and therefore increased prevalence of the new gene in the gene pool.

Types of Selection  Example: beak size in finches  Example: human birth weight  The “extremes” are preferred – leads to speciation.

Speciation  Species = group of individuals that actually (or potentially) interbreed

Speciation  Species = group of individuals that actually (or potentially) interbreed  Speciation = the splitting of one lineage into two or more lineages

Speciation  Species = group of individuals that actually (or potentially) interbreed  Speciation = the splitting of one lineage into two or more lineages  Allopatric speciation  geographic isolation

Speciation  Species = group of individuals that actually (or potentially) interbreed  Speciation = the splitting of one lineage into two or more lineages  Allopatric speciation  geographic isolation  Sympatric speciation  members of a population become better adapted within a particular “niche” in the ecosystem.

Speciation  Species = group of individuals that actually (or potentially) interbreed  Speciation = the splitting of one lineage into two or more lineages  Allopatric speciation  geographic isolation  Sympatric speciation  members of a population become better adapted within a particular “niche” in the ecosystem.  Parapatric speciation  individuals are more likely to mate with their geographic neighbors.

Natural Selection Simulation  Have a chat about the weather in your area. The only hitch is that you may not use the letter 'e' in anything that you type. Any words that contain the letter 'e' will be ignored. You and your classmates will talk about the weather in your area for five minutes total, after which your instructor will announce "STOP," and you will be allowed to use the letter 'e' again.

Natural Selection Simulation  In your new, 'e'-free environment, what adaptations to language did you and your classmates make? What things were more difficult to talk about, and why?  If you were to live in a 'u'-free environment, what other letters might struggle and die out?  Think about this experiment as a way to show how changes in environment force creatures (like you) to adapt and change. Now, think about squirrels. What might happen to them if all the oak trees (and therefore acorns) died out? What adaptations might they have to make to adjust to the acorn-free world? How might these changes affect their body structures? After 50,000 years of living in an acorn- free world, how might squirrels look? Why does this kind of evolutionary change take so long?

Next week:  Unit 7: The Human Practice of Science  Reading: Atoms and Biochemistry