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Professor: Hufford/Biederman S.I. Leader: Stephanie Schneider Biology 211 (2) Week 12! Chapter 27! KEY CONCEPTS:! 1. Compare and contrast allopatric and sympatric speciation. Which is more common? a. Allopatric: Speciation that begins with geographic isolation b. Sympatric: Speciation that occurs in the same geographic area due to the result of their genetic isolation 2. What are the 3 most common approaches for identifying species? a. 1) The biological species concept b. 2) The morphospecies concept c. 3) They phylogenetic species concept 3. State the biological species concept in your own words. What are the advantages and disadvantages of this species concept? Name and describe the tow mechanisms that stop gene flow between populations. a. According to the biological species concept, different species are reproductively isolated from each other. They either do not interbreed, or they fail to produce viable fertile offspring b. Advantage: Reproductive isolation=evolutionary independence c. Disadvantages: Reproductive isolation cannot be evaluated in fossils or species that reproduce asexually, and cannot be applied only to populations that overlap geographically d. Prezygotic isolation: Individuals of different species are prevented from mating e. Postzygotic isolation: Individuals from different populations do mate, but the hybrid offspring do not survive or reproduce Prezygotic Isolation Process Example Temporal Populations are isolated because they breed at different times. Bishop pines and Monterey pines release their pollen at different times of the year Habitat Populations are isolated because they breed in different habitats Parasites that begin to exploit new host species are isolated from their original population Professor: Hufford/Biederman S.I. Leader: Stephanie Schneider Prezygotic Isolation Process Example Behavioral Populations do not interbreed because their courtships displays differ To attract male fireflies, female fireflies give a species-specific sequence of flashes Gametic Barrier Matings fail because eggs and sperm are incompatible In sea urchins, a protein called bindin allows sperm to penetrate eggs. Differences in the amino acid sequence of bindin cause matings to fail between closely related populations Mechanical Matings fail because male and female reproductive structures are incompatible In alpine skypilots (a flowering plant), the length of the floral tube varies. Bees can pollinate in populations with short tubes, but only hummingbirds can pollinate in populations with long tubes. Postzygotic Isolation Process Example Hybrid viability Hybrid offspring do not develop normally and die as embryos When ring-necked doves mate with rock doves, less than 6% of eggs hatch. Hybrid sterillity Hybrid offspring mature but are sterile as adults Eastern meadowlarks and western meadowlarks are almost identical morphologically, but their hybrid offspring are usually infertile. 4. What is the main criterion for identifying populations as different species according to the morphospecies concept? What are advantages and disadvantages of this concept? a. According to the morphospecies concept, individual species differ in size, shape, or other morphological features b. Advantage: Widely applicable c. Disadvantage: This concept is subjective 5. Why are cryptic species a problem for the morphospecies concept? a. It cannot identify cryptic species—a species that cannot be distinguished from similar species by easily identifiable morphological traits 6. How are species classified according to the phylogenetic species concept? What is a monophyletic group? What are the advantages and disadvantages of this species concept? a. The phylogenetic species concept identifies species based on evolutionary history b. A monophyletic group consists of an ancestral population plus all of its descendants; these groups are identified by synapomorphies Professor: Hufford/Biederman S.I. Leader: Stephanie Schneider c. Advantages: It can be applied to any population, and it is logical d. Disadvantages: Phylogenies are currently available for only a tiny subset of populations of the tree of life; critic point out that it would probably lead to recognition of many more species than either of the other species concepts 7. In actual practice, researchers use which of the species concepts to identify evolutionary independent populations in nature? a. All three species concepts 8. Compare and contrast speciation by dispersal and speciation by vicariance. Are these forms of sympatry, allopatry or both? The formation of the isthmus of Panama caused speciation by which process (dispersal or vicariance)? a. Dispersal: A population moves to a new habitat, colonizes it, and forms a new population b. Vicariance: A physical barrier splits a widespread population into subgroups that are physically isolated c. These are forms of Allopatry d. Vicariance of the snapping shrimp