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Adapted from The Biology Space (Lee Ferguson, Allen High School) Topic Review Guide: Speciation To Think About: How is natural selection a major mechanism of evolution? Watch: Mr. Andersens”s Reproductive Isolation and Speciation video Then: Mr. Andersen’s Speciation and Extinction video. Read: Chapter 13 and 14 Supplementary Resources: click the links below for more information to help you learn more about the lesson. Crash Course’s Speciation video Kimball’s Biology Pages: Speciation UC Berkeley’s Understanding Evolution: Speciation UC Berkeley’s Understanding Evolution: Evo-Devo University of Miami: Reproductive Isolation DNA from the Beginning: Master Genes Control Basic Body Plans Listen and Look: Here is a list of key terms you will hear and see during this lesson. Get to know them! Be able to connect them to one another using a concept map. KEY TERMS: Speciation Speciation Species Polyploidy Temporal isolation Gradualism Extinction Pre-zygotic barrier Gene flow Behavioral isolation Evo-devo Reproductive isolation Geographic isolation Allopatric speciation Mechanical isolation Punctuated equilibrium Adaptvie radiation Post-zygotic barrier Sympatric speciation hybrid hybrid stability Recall and Review: Use the lecture in the videos and your textbook to help you answer these questions in your BILL: 1. Explain what the biological species concept is. Why is this species concept inapplicable to asexually reproducing organisms? A species is a group of individuals that can reproduce together and produce fertile offspring. Asexually organisms do not apply here because they do not reproduce with other members of their species. 2. In the “Speciation and Extinction” podcast, Mr. Andersen discusses speciation of two varieties of stickleback fish. Describe the environmental pressure that drove the process of speciation in these fish and the role that natural selection played in this process. 3. Explain why island systems are ideal locations for the process of adaptive radiation to take place. Describe other situations that could create ideal conditions for adaptive radiation to occur. They are ideal because the species are confined to the new islands and thus only those fit for that specific environment can survive. The species will evolve quickly as the alleles that cannot survive will die off quick. 4. Explain what makes reproductive isolation such an important component of the species concepts discussed in the chapter. In order for a new species to form, there must be a small number of alleles reproducing over and over together. When individuals of one species become isolated from the rest of the population, they can only reproduce with others who are separated thus separating them genetically from the original population. Adapted from The Biology Space (Lee Ferguson, Allen High School) 5. Draw an example of each of the following examples of reproductive isolation. Your drawing should explain how each type of isolation leads to the formation of a new species without using any words. a. Geographic isolation (live in two different regions) b. Behavioral isolation (different dances or songs in birds) c. Temporal isolation (reproducing in the spring vs fall) d. Mechanical isolations (2 snails with opposite shell openings) 6. Explain why reproductive barriers evolve. Describe an example of the evolution of a prezygotic barrier and the evolution of a postzygotic barrier. They evolve because of the barriers listed above. Prezygotic barriers prevent the two organisms from any chance of coming together to mate. Postzygotic barriers allow for fertilization to occur. However, once it occurs, the zygote typically is not viable thus an offspring does not form. 7. Explain why polyploidy is much more common in plant species than in animal species. How can polyploidy lead to reproductive isolation? Because of alternation of generation – since they have to already undergo a change in chromosome number during the cycle. Also they have more flexible body plans than animals. As polyploidy leads to a completely different number of chromosomes, it is likely it would lead to reproductive isoloation. 8. Recall that sexual selection is the process by which females of a species seeing a mate select the males of their species based on an attractive appearance or behavior. Explain how sexual selection could lead to reproductive isolation. If a sub population of females changes their preference of dance or color (even if it is a minute change) they will begin to only reproduce with birds who do that dance and will refuse to mate with the others. 9. Distinguish between allopatric and sympatric speciation. Give two examples of each type of speciation. (Allopatric speciation is when there is some sort of geographic barrier that forms and separates members of the same population. Ex: formation of a lake that separates species of ground squirrel. Sympatric speciation is when there is no barrier between the members of the population yet they quit reproducing with certain members. For example, a group of trees separates in that the center trees begin reproducing together – maybe less wind or mammals to spread the seeds to the outer trees. 10. Discuss the differences between the two schools of thought regarding the tempo of evolutionary change: punctuated equilibrium versus gradualism. 11. Look at the DNA from the Beginning site that discusses the role of genetics in development of embryos. Homeotic genes (Hox) are genes that control the basic body plan of an organism. How do you think natural selection coupled with the expression of Hox genes in early animal embryos played a role in tetrapod evolution.