-11.3 - 11.5 - 11.6 -

1. -11.3 - 11.5 - 11.6 - Mechanisms of Evolution Speciation Through Isolation Patterns of Evolution

2. Think About It: • 1776 United States Became Independent • Where were the original settlers from? • Was there an abundance of variation in this population? • How has immigration had an effect on genetic variation in the US? • Leads to increased genetic variation in the population by adding new alleles to the gene pool.

3. Gene Flow • Defined: • The movement of alleles from one population to another. • Break it Down: • New Alleles to new population, loss of alleles in another. • Increases genetic variation. • How does it affect nearby populations? • What does a lack of gene flow lead to?

4. Genetic Drift • Small populations more likely to be affected by random chance. • Allele frequency changes due to chance is called genetic drift. • Two processes cause pop. to become small enough for this phenomenon: • Bottleneck effect • Founder Effect

5. Bottleneck Effect • Defined: • Genetic drift that occurs after an event greatly reduces the size of a population.

6. Founder Effect • Genetic drift due to a small number of individuals of a population colonizing a new area.

7. Effects of Genetic Drift • Loss of genetic variation. • Less likely to be able to adapt to changes • Lethal alleles can become more common in gene pool.

8. Effect of Mating • Males: • Sperm production is constant, .: they are less selective in the mate they choose. • More chances = less selective • Females: • Production is limited in every reproductive cycle. • Less chances = more selective. • Sexual selection: • Certain traits increase mating success.

9. Intra/Intersexual Selection • Intrasexual: • Competition among males. • Intersexual: • Males display traits that attract female. • http://dsc.discovery.com/videos/planet-earth-jungles-birds-of-paradise.html • Some traits are not adapted for survival.

10. Brain Break #1 • The sun’s surface is approx: 5505 degrees Celsius. Keep this in mind. • If you are standing next to a hot stove you can feel the heat. • As you get farther away you should feel less heat. • That is basic science, the farther you are from a heat source the less it affects you. • The Solar Corona (an area not to far from the sun) has a temperature of 1.5 million degrees Celsius. • How is this possible?

11. 11.5 Speciation Through Isolation • How do we know that a miniature poodle and a great dane are the same species? • At what point would the two breeds become separate species?

12. Isolation of Populations: • If gene flow stops, populations are isolated. • Adaptation is never ending • Leads to gene pool changes. • Over time, changes add up & isolated populations become more and more genetically different • Behavior and phenotypes may change as well.

13. Reproductive Isolation • Defined: • When members of different populations can no longer mate successfully with one another. • Analyze: • The final step in becoming separate species. • Discuss: • Talk with your neighbor for 1 minute and come up with an example of Isolation in nature. Be prepared to share! 60 Seconds starts NOW!

14. Speciation Socially Awkward Penguin • Defined: • The rise of two or more species from one existing species • BUT Mr. Wilson…..! • How does isolation occur so that new species can be formed?! • Great Question! There are three ways that populations can become isolated! Behavioral Barriers Temporal Barriers Geographic Barriers

15. Behavioral Isolation • Behavior changes can prevent mating between populations. • Defined: • Isolation caused by differences in courtship or mating behaviors. • Examples: • Fireflies flash patterns • Chemical scents • Courtship songs/dances with birds

16. Geographic Isolation • Defined: • Physical barriers that divid a population into two or more groups. • What kind of barriers you ask? • Rivers, mountains, rivers, anything! • Examples: • Pacific/Atlantic species separated by the Panama Isthmus • Shrimp • Grand Canyon & Squirrels Just pretend they’re shrimp OK?!

17. Temporal Isolation • Defined: • When timing prevents reproduction between populations. • Courtship period • Time of Day • Time of Year • Based on competition • Example:

18. Temporal Isolation American Toad Mates Early Summer Fowlers Toad Mates Late Summer

19. Brain Break #2 : I Will Try to Read Your Mind! • No Guarantees & You Have to Be Good at Math! • Pick a Number between 1 and 10. • Multiply it by 9 • Add the two Digits of the resulting number together (if you picked 1 just deal with it) • Now Subtract 5 From it…. • You should have a number now…think of the corresponding letter in the alphabet (A=1, B=2, etc.)

20. Brain Break #2 : I Will Try to Read Your Mind! • Pick a country that starts with that letter. Any Country… So if you had F, Finland would work. • Once you have your country use the last letter of that country and think of an animal. Finland = D = Dog • Once you have your animal take the last letter of that animals name and think of a color. Dog = G = Green! • You Have it?....ok here I go…

22. 11.6 - Patterns of Evolution • Mutation and Genetic Drift cannot be predicted. • Random Events • Natural Selection is NOT random. • Beneficial traits increase survival • Natural Selection has direction • But this direction is controlled by the environment NOT the population

23. Convergent Evolution • Scenario: • Zombie Apocalypse • Zombies will also eat small rats • Humans or Rats with tough skin pose a challenge to zombie rotted teeth. • Both species begin to develop similar characteristics in their skin making it tougher. • Convergent Evolution • Shark/fish tails, bird / butterfly feathers (analogous structures).

24. Divergent Evolution • Defined: • When closely related species evolve in different directions.

25. Coevolution • Sometimes a change in one species can result in a change in another. • Coevolution: • The process by which two or more species evolve in response to changes in each other. • Example: • Stinging Ants & The Bull-thorn acacia

26. Coevolution in competition • Competitive species can also coevolve: • Plants developing defense chemicals to avoid consumption by herbivores. • Crabs eat snails  snails develop bigger spiked shells  crabs develop more powerful claws … etc

27. Extinction • Defined: • The elimination of a species from earth. • How? • Failure to adapt, hunting, fishing, etc.

28. Speciation follows a Pattern • Punctuated Equillibrium • Episodes of speciation occur suddenly • Followed by long periods of little evolutionary change. • Adaptive Radiation • Diversification of an ancestor into many descendant species.

29. End of Notes