Evolution of New SpeciesEvolution of New Species

Changes in populations may Changes in populations may lead to the formation of new lead to the formation of new

species.species.

What is a biological species?What is a biological species?

• A group of interbreeding organisms A group of interbreeding organisms that produce viable fertile offspring.that produce viable fertile offspring.

• Examples: all humans! Examples: all humans!

Eastern box turtlesEastern box turtles

Natural Selection may lead to Natural Selection may lead to speciationspeciation

• There are types of selection:There are types of selection:

• DirectionalDirectional

• StabilizingStabilizing

• DisruptiveDisruptive

Stabilizing SelectionStabilizing Selection

• Selection against Selection against two extremestwo extremes

Example – average Example – average weight of human weight of human babies at birthbabies at birth

Direcional SelectionDirecional Selection

• Natural SelectionNatural Selection

Causes the species Causes the species to to

Change in a certainChange in a certain

DirectionDirection

Example – bird beaksExample – bird beaks

Disruptive SelectionDisruptive Selection

• Selection in two Selection in two directions away directions away from a mean.from a mean.

• Two groups of Two groups of organisms exist organisms exist with very different with very different features to exploit features to exploit different resources.different resources.

SpeciationSpeciation

• Evolution of new species occurs Evolution of new species occurs when some barrier keeps organisms when some barrier keeps organisms from interbreeding.from interbreeding.

How do new species arise?How do new species arise?

• Once a population of organisms no Once a population of organisms no longer interbreeds successfully with longer interbreeds successfully with another population – two species another population – two species have evolved from one.have evolved from one.

• How does this separation occur?How does this separation occur?• Sometimes natural selection will Sometimes natural selection will

divide species.divide species.• How might directional selection lead How might directional selection lead

to a new species?to a new species?(Hand out the paper.)(Hand out the paper.)

Geographic IsolationGeographic Isolation

• Physical barrier Physical barrier divides a divides a population and population and they no longer they no longer interbreedinterbreed

• Darwin’s Darwin’s Galapagos finches Galapagos finches are an excellent are an excellent example.example.

Reproductive IsolationReproductive Isolation

• Formerly Formerly interbreeding interbreeding organisms in organisms in the same the same location no location no longer mate longer mate and produce and produce fertile fertile offspringoffspring

Adaptive Radiation=Divergent Adaptive Radiation=Divergent evolutionevolution

• New species arise New species arise when resources are when resources are limited and certain limited and certain groups of organisms groups of organisms live in different niches live in different niches and as a result no and as a result no longer interbreed.longer interbreed.

• One common One common ancestor leads to ancestor leads to many different many different speciesspecies

Convergent evolutionConvergent evolution

• Unrelated species in Unrelated species in similar environments similar environments share similar share similar pressures and thus pressures and thus develop similar develop similar traits.traits.

• Example: wings for Example: wings for flying flying animals=analogous, animals=analogous, not homologousnot homologous

Adaptive Radiation=Divergent Adaptive Radiation=Divergent evolutionevolution

• New species arise New species arise when resources are when resources are limited and certain limited and certain groups of organisms groups of organisms live in different niches live in different niches and as a result no and as a result no longer interbreed.longer interbreed.

• One common One common ancestor leads to ancestor leads to many different many different speciesspecies

21. Adaptive 21. Adaptive radiation=divergent evolution radiation=divergent evolution or convergent evolutionor convergent evolution

• The “tree of life” The “tree of life” shows common shows common ancestry of all ancestry of all living organismsliving organisms

22. Geographic or reproductive 22. Geographic or reproductive isolation? isolation?

• Female birds prefer Female birds prefer “showy” mates “showy” mates therefor etherefor e

• Female birds prefer Female birds prefer “showy” mates “showy” mates therefore female therefore female birds will mate with birds will mate with only the male of only the male of their speciestheir species

Quiz Time!!!!Quiz Time!!!!

• Number 1-20 on a piece of scrap Number 1-20 on a piece of scrap paper.paper.

• In each slide an example will be In each slide an example will be shown.shown.

• Determine the type of selection or Determine the type of selection or isolation indicated in the slide.isolation indicated in the slide.

Hey buddy, why don’t you hitch a ride. May be we can hook up?!

We are different species!

1. Geogrpahic or reproductive isolation

2. Adaptive radiation = divergent evolution or convergent evolution?

3. Reproductive or geographic 3. Reproductive or geographic Isolation?Isolation?

These fish live in the same pond, but do not interbreed.

4. Geographic or 4. Geographic or reproductivereproductive

• Two species live in different habitatsTwo species live in different habitats

• Species that breed during different Species that breed during different times of the year, different seasons times of the year, different seasons or different years are not able to or different years are not able to mate.mate.

5. Reproductive or geographic

6. Divergent or convergent evolution

In plants and animals, flower structure or In plants and animals, flower structure or body parts forbid mating body parts forbid mating 7. reproductive or geographic isolation?7. reproductive or geographic isolation?

• Anatomically incompatible = parts do Anatomically incompatible = parts do not fit!not fit!

OH No!!!!!!

8. Geographic or reproductive isolatio?

9. Divergent or convergent evolution

Originally there was one species of Originally there was one species of mouse existed – now a mountain mouse existed – now a mountain range exists, they no longer range exists, they no longer interbreedinterbreed..10. geographical or reproductive?10. geographical or reproductive?11. divergent or convergent?11. divergent or convergent?

12. Convergent or divergent12. Convergent or divergent13. analogous or 13. analogous or homologous?homologous?

14. Geographical or 14. Geographical or reproductive isolation?reproductive isolation?

• Signals get crossed – incorrect Signals get crossed – incorrect mating dance in birds or insects.mating dance in birds or insects.

15.15.. . Convergent or divergent?Convergent or divergent?16. Analagous or homolgous?16. Analagous or homolgous?

17. Divergent or convergent 17. Divergent or convergent evolution?evolution?18. analogous or 18. analogous or homologous?homologous?

Originally there was one species of Originally there was one species of shrimp existed – now that the isthmus shrimp existed – now that the isthmus of Panama exists, they no longer of Panama exists, they no longer interbreedinterbreed..19. geographical or reproductive?19. geographical or reproductive?20. divergent or convergent?20. divergent or convergent?