The Origin of Species

Transcription

1 The Origin of Species Bowerbirds, native to New Guinea and Australia, are named for the structure, called a bower, that the male weaves from twigs and grasses to attract females. After building his bower, the male collects objects such as fruits, seeds, insect parts, rocks, flowers, and leaves and arranges them artfully by color and type Pearson Education, Inc.

2 Figure Females are dull colored (as are males) and tour the bowers of local males, inspecting each while its owner courts her with a song and dance. Vogelkop bowerbird photograph by Barrie Britton

3 2012 Pearson Education, Inc. DEFINING SPECIES

4 14.2 There are several ways to define a species The biological species concept defines a species as a group of populations, whose members have the potential to interbreed in nature, and produce fertile offspring. Therefore, members of a species are similar because they reproduce with each other Pearson Education, Inc.

5 14.2 There are several ways to define a species Reproductive isolation prevents members of different species from mating with each other, maintains separate species Pearson Education, Inc.

6 Figure 14.2C Hybridization between two species of bears Grizzly bear Polar bear Hybrid grolar bear

7 14.3 Reproductive barriers keep species separate Reproductive barriers serve to isolate the gene pools of species and prevent interbreeding. Depending on whether they function before or after zygotes form, reproductive barriers are categorized as prezygotic or postzygotic Pearson Education, Inc.

8 14.3 Reproductive barriers keep species separate Five types of prezygotic barriers prevent mating or fertilization between species. 1. In habitat isolation, two species live in the same general area but not in the same kind of place. 2. In temporal isolation, two species breed at different times (seasons, times of day, years) Pearson Education, Inc.

9 Figure 14.3 Habitat isolation (lack of opportunities to encounter each other) The garter snake Thamnophis atratus lives mainly in water. The garter snake Thamnophis sirtalis lives on land.

10 Figure 14.3 Temporal isolation (breeding at different times or seasons) The eastern spotted skunk (Spilogale putorius) breeds in late winter. The western spotted skunk (Spilogale gracilis) breeds in the fall.

11 14.3 Reproductive barriers keep species separate Prezygotic Barriers, continued 3. In behavioral isolation, there is little or no mate recognition between females and males of different species. 4. In mechanical isolation, female and male sex organs are not compatible. 5. In gametic isolation, female and male gametes are not compatible Pearson Education, Inc.

12 Figure 14.3 Behavioral isolation (different courtship rituals) The blue-footed booby (Sula nebouxii) performs an elaborate courtship dance. The masked booby (Sula dactylatra) performs a different courtship ritual.

13 Figure 14.3 Mechanical isolation (physical incompatibility of reproductive parts) Heliconia latispatha is pollinated by hummingbirds with short, straight bills. Heliconia pogonantha is pollinated by hummingbirds with long, curved bills.

14 Figure 14.3 Gametic isolation (molecular incompatibility of eggs and sperm or pollen and stigma) Purple sea urchin (Strongylocentrotus purpuratus) Red sea urchin (Strongylocentrotus franciscanus)

15 14.3 Reproductive barriers keep species separate Three types of postzygotic barriers operate after hybrid zygotes have formed. 1. In reduced hybrid viability, most hybrid offspring do not survive. 2. In reduced hybrid fertility, hybrid offspring are vigorous but sterile. 3. In hybrid breakdown, the first-generation hybrids are viable and fertile but the offspring of the hybrids are feeble or sterile Pearson Education, Inc.

16 Figure 14.3 Reduced hybrid viability (hybrid development or survival impaired by interaction of parental genes) Some salamander species can hybridize, but their offspring do not develop fully or are frail and will not survive long enough to reproduce.

17 Figure 14.3 Reduced hybrid fertility (vigorous hybrids that cannot produce viable offspring) A mule is the sterile hybrid offspring of a horse and a donkey.

18 Figure 14.3 Hybrid breakdown (viable and fertile hybrids with feeble or sterile offspring) The rice hybrids on the left and right are fertile, but plants of the next generation (middle) are sterile.

19 MECHANISMS OF SPECIATION 2012 Pearson Education, Inc.

20 14.4 In allopatric speciation, geographic isolation leads to speciation In allopatric speciation, populations of the same species are geographically separated, isolating their gene pools. Isolated populations will no longer share changes in allele frequencies caused by natural selection, genetic drift, and/or mutation Pearson Education, Inc.

21 14.4 In allopatric speciation, geographic isolation leads to speciation Gene flow between populations is initially prevented by a geographic barrier. For example the Grand Canyon and Colorado River separate two species of antelope squirrels, and the Isthmus of Panama separates 15 pairs of snapping shrimp Pearson Education, Inc.

22 Figure 14.4A Allopatric speciation of geographically isolated antelope squirrels (Ammospermophilus) South rim A. harrisii A. leucurus North rim

23 Figure 14.4B Allopatric speciation in snapping shrimp (Alpheus) A. formosus A. nuttingi ATLANTIC OCEAN Isthmus of Panama PACIFIC OCEAN A. panamensis A. millsae