CHAPTER 24 THE ORIGIN OF SPECIES

1. CHAPTER 24 THE ORIGIN OF SPECIES Different Species Of Japanese Ants!!! What is a species ? How does speciation occur ?

2. Mutations + Sexual recombination + genetic drift +gene flow + natural selection! = Macroevolution: --the origin of new species, genera, families, orders, classes, phyla, and kingdoms Speciation—the origin of new species

3. SPECIES “kind”-”appearance” – group of populations whose members can interbreed and produce fertile offspring; • A biological species is the largest set of populations in which genetic exchange is possible and is genetically isolated from other populations. Different Species Of HUMANS??? What is a species ? How does speciation occur ?

4. Distinctions between species are not always clear. Subspecies have small differences from other subspecies and usually have geographical variation. C. hutchinsii hutchinsii C. canadensis canadensis

5. Concepts of species: • Biological species concept—reproductive isolation • Morphological species concept—measurable • anatomical differences between species • 3. Ecological species concept— based on the ‘niche’ – environment and organisms’ role in using it • 4. Pluralistic species concept—cohesion of (2) and (3)

6. Situation: 2 populations that are microevolving (different p,q) -what will make them 2 species? -not having fertile offspring! Prezygotic barriers Post zygotic barriers

7. Organisms of different species cannot interbreed for a number of reasons. • Prezygotic barriers- hinder fertilization • Habitat isolation—live in different places ex: water vs. terrestrial in garter snakes

8. 2) behavioral isolation—respond only to members of the same species; ex: firefly flashes Prezygotic barriers hinder fertilization Ex. Firefly flashes, Bower Bird nest

9. Prezygotic barriers hinder fertilization 3) temporal isolation—different breeding times (ex. W. and E. skunks) EASTERN- summer WESTERN - winter

10. Prezygotic barriers hinder fertilization 4) mechanical isolation—anatomical incompatibility Ex. Damsel fly genitalia, flowers

11. Prezygotic barriers hinder fertilization 5) gametic isolation—gametes may not be recognized by other species for fertilization (molecular recognition missing between egg and sperm)

12. Postzygotic barriers - gametes can get together to make a zygote, BUT barriers prevent a zygote from developing properly

13. Postzygotic barriers prevent a zygote from developing properly. • Reduced hybrid viability—development is aborted at some embryonic stage. Ex. frogs

14. Postzygotic barriers prevent a zygote from developing properly. 2. Reduced hybrid fertility—hybrids are sterile—usually there is a failure of meiosis in these hybrids so they cannot produce viable (good) gametes

15. Postzygotic barriers prevent a zygote from developing properly. 3) hybrid breakdown—first-generation hybrids may be fertile, but second-generation offspring are not viable. Ex. cotton

16. SUMMARY

19. Recipe to make a New Species: Need to create a barrier for gene flow within a population- that is a barrier for productive SEX Need to maintain this barrier (prezygotic/postzygotic) so that the two groups can continue accumulating differences through mutation/sexual recombination (acted upon by natural selection - of course you knew that!) And then PRESTO! You have a new species (give or take a million years!) Anagenesis = one species changes into another Cladogenesis = branching of a new species from a species that continues to exist

20. How do new species arise (barrier creation) • Allopatric speciation (“other homeland”) • Sympatric speciation (“together”)

21. Allopatric Speciation --occurs when geographical barriers block gene flow *small populations are more likely to change enough to become a new species RING SPECIES

22. HAWAIIN HONEYCREEPERS 'I'IWI - Vestiaria coccineaFound in 'ohi'a lehua forests.  Feeds on the nectar of 'ohi'a lehua flowers high in the forest canopy and from tubular blossoms in the understory. 'AMAKIHI - Hemignathus virensCommon in native forests above 2,000 feet.  Feeds more on insects and is less dependant on nectar.  Female is a darker, olive green color. PALILA - Loxioides bailleuiEndangered Found only in the dry forests on the slopes of Mauna Kea, Big Island, 6,000 to 9,000 feet. 'AKOHEKOHE - Palmeria dolei Crested honeycreeper - Endangered Found only in the rain forests of east Maui at elevations of 4,500 to 6,500 feet.

23. Adaptive radiation— evolution of many different species from a common ancestor *common on islands*

24. gene pool at the edge is probably different • (founder effect) • 2. until the peripheral population becomes larger, • genetic drift will occur • 3. natural selection may be different in the fringe • environment Peripheral isolate = small population at the fringe of a larger population’s range --good candidate for speciation

25. Sympatric Speciation --a new species can evolve without geographic isolation --genetic changes can prevent members of the same species from mating ex. Apple maggot flies, polyploid plants

26. Sympatric Speciation --a new species can evolve without geographic isolation -- female lays egg where she grew up Apples (introduced to US by immigrants) Apple Maggot Flies Hawthorns (native to US)

27. One species=autopolyploid Tetraploid plants can’t interbreed with normal plantspostzygotic barrier 2 different species form an allopolyploid hybridthese usually propagate asexually (sympatric or allopatric?)

28. Wheat evolved from 2 meiotic errors.

29. What type of speciation is this?

30. Speciation is at the boundary between microevolution (population allelle frequency change) and macroevolution (accumulation of change over millions of years).

31. Rate of Speciation -Gradualism vs. Punctuated Equilibrium Gradualism—species diverge gradually over a long period of time Punctuated equilibrium—species diverge in spurts of relatively rapid change --long periods of equilibrium punctuated by short periods of speciation

33. Development genes are important in macroevolution. Allometric growth—difference in relative rates of growth of various parts of the body

34. Paedomorphosis—adult retains features that were juvenile structures in its ancestors. ex. some salamanders retain gills

35. Heterochrony, an evolutionary change in the rate or timing of developmental events.

36. Temporal changes in development that differ between species--heterochrony Homeosis = alteration in basic body design controlled by small sets of gene in development—homeotic genes (Hox complex)

37. Evolution is not goal-oriented--species selection produces an evolutionary trend