Evolution of New Species Changes in populations may lead to the formation of new species.

What is a biological species? A group of interbreeding organisms that produce viable fertile offspring. A group of interbreeding organisms that produce viable fertile offspring. Examples: all humans! Examples: all humans! Eastern box turtles Eastern box turtles

Natural Selection may lead to speciation There are types of selection: There are types of selection: Directional Directional Stabilizing Stabilizing Disruptive Disruptive

Stabilizing Selection Selection against two extremes Selection against two extremes Example – average weight of human babies at birth

Direcional Selection Natural Selection Natural Selection Causes the species to Change in a certain Direction Example – bird beaks

Disruptive Selection Selection in two directions away from a mean. Selection in two directions away from a mean. Two groups of organisms exist with very different features to exploit different resources. Two groups of organisms exist with very different features to exploit different resources.

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

How do new species arise? Once a population of organisms no longer interbreeds successfully with another population – two species have evolved from one. Once a population of organisms no longer interbreeds successfully with another population – two species have evolved from one. How does this separation occur? How does this separation occur? Sometimes natural selection will divide species. Sometimes natural selection will divide species. How might directional selection lead to a new species? How might directional selection lead to a new species? (Hand out the paper.)

Geographic Isolation Physical barrier divides a population and they no longer interbreed Physical barrier divides a population and they no longer interbreed Darwin’s Galapagos finches are an excellent example. Darwin’s Galapagos finches are an excellent example.

Reproductive Isolation Formerly interbreeding organisms in the same location no longer mate and produce fertile offspring Formerly interbreeding organisms in the same location no longer mate and produce fertile offspring

Adaptive Radiation=Divergent evolution New species arise when resources are limited and certain groups of organisms live in different niches and as a result no longer interbreed. New species arise when resources are limited and certain groups of organisms live in different niches and as a result no longer interbreed. One common ancestor leads to many different species One common ancestor leads to many different species

Convergent evolution Unrelated species in similar environments share similar pressures and thus develop similar traits. Unrelated species in similar environments share similar pressures and thus develop similar traits. Example: wings for flying animals=analogous, not homologous Example: wings for flying animals=analogous, not homologous

Adaptive Radiation=Divergent evolution New species arise when resources are limited and certain groups of organisms live in different niches and as a result no longer interbreed. New species arise when resources are limited and certain groups of organisms live in different niches and as a result no longer interbreed. One common ancestor leads to many different species One common ancestor leads to many different species

21. Adaptive radiation=divergent evolution or convergent evolution The “tree of life” shows common ancestry of all living organisms The “tree of life” shows common ancestry of all living organisms

22. Geographic or reproductive isolation? Female birds prefer “showy” mates therefor e Female birds prefer “showy” mates therefor e Female birds prefer “showy” mates therefore female birds will mate with only the male of their species Female birds prefer “showy” mates therefore female birds will mate with only the male of their species

Quiz Time!!!! Number 1-20 on a piece of scrap paper. Number 1-20 on a piece of scrap paper. In each slide an example will be shown. In each slide an example will be shown. Determine the type of selection or isolation indicated in the slide. Determine the type of selection or 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 Isolation? These fish live in the same pond, but do not interbreed.

4. Geographic or reproductive Two species live in different habitats Two species live in different habitats

Species that breed during different times of the year, different seasons or different years are not able to mate. Species that breed during different times of the year, different seasons or different years are not able to mate. 5. Reproductive or geographic

6. Divergent or convergent evolution

In plants and animals, flower structure or body parts forbid mating 7. reproductive or geographic isolation? Anatomically incompatible = parts do not fit! Anatomically incompatible = parts do not fit! OH No!!!!!!

8. Geographic or reproductive isolatio? 9. Divergent or convergent evolution

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

12. Convergent or divergent 13. analogous or homologous?

14. Geographical or reproductive isolation? Signals get crossed – incorrect mating dance in birds or insects. Signals get crossed – incorrect mating dance in birds or insects.

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

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

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