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Biology 11AP Chapter 24 The Origins of Species p. 488 Essential knowledge 1.c.1 Speciation and extinction have occurred throughout the Earth’s history. 1.c.2 Speciation may occur when two populations become reproductively isolated from each other. 1.c.3 Populations of organisms continue to evolve. Chapters/sections 24.3, 24.4, 25.4 24.1 24.2 Illustrative examples covered • Five major extinctions • Human impact on ecosystems and species extinction rates No illustrative examples listed in the Curriculum Framework. • Chemical resistance (mutations for resistance to antibiotics, pesticides, herbicides or chemotherapy drugs occur in the absence of the chemical) • Emergent diseases • Observed directional phenotypic change in a population (Grants’ observations of Darwin’s finches in the Galapagos) • A eukaryotic example that describes evolution of a Structure or process such as heart chambers, limbs, the brain and the immune system What is speciation? Also referred to as macroevolution in which new species evolve. It also explains the differences and similarities between species. __ How does the DNA of this flightless cormorant from the Galapagos Islands compare to the DNA of cormorants from the west coast of South America? Similar What does this suggest? That the flightless cormorant may have originated from a south American ancestor. What is the difference between microevolution and macroevolution? Microevolution involves a change in the allele frequency within a population while macroevolution requires a change that leads to a new species. What is the biological definition of a species? ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ _____________________ What causes members of a species to resemble each other more than they resemble other species See: http://www.pbs.org/wgbh/evolution/library/05/2/l_052_04.html on hummingbird evolution in the Andes What is reproductive isolation? ____________The inability to produce viable offspring. ______________________________________________________________________________ ______ Reproductive isolation blocks the reproduction of ___hybrid offspring__, which are offspring that result from interspecific mating. Here are various prezygotic reproductive barriers: (prevent zygote from forming) page 490 And here are some postzygotic reproductive barriers: Do these salamanders belong to the same species? What is allopatric speciation? _ Formation of new species as a result of geographic barriers. Takes thousands of years. Here is an example of allopatric speciation in antelope squirrels on opposite rims of the Grand Canyon: Allopatric speciation in frog species can be seen to be related to the movement of landmasses: What do the data in the graph below show is the relationship between reproductive isolation and distance between populations of dusky salamanders? ______________________________________________________________________________ ______________________________________________________________________________ _________ Here is an experiment with fruit fly populations that were experimentally separated and raised under different conditions . What does the experiment demonstrate? _______________ allopataric speciation in process Does a geographic barrier always result in speciation? What is sympatric speciation? __________________Speciation where there is no geographic barrier. Eg in Lake Malawi where different species of cichlid fish evolved at different depths and areas of the lake. See figure 24.12 The development of polyploids in plants is an excellent example of sympatric speciation. What is an autopolyploid? _______________________________________________________________ ______________________________________________________________________________ _______ What causes the tetraploid organism to be reproductively isolated from the diploid organism? ______________________________________________________________________________ _______ Sympatric speciation can also occur through allopolyploidy, as shown below: (more common) Fig 24.11 What are some important crops that are polyploids? _________________________________________ Here is an example of how sympatric speciation can occur through sexual selection. These are cichlids from Lake Victoria in Africa: (see p 497 for details of the experiment. Section 24.3 What is a hybrid zone? __________________________________________________________________ This diagram illustrates the structure of a hybrid zone between two toad species in Europe: Here is a diagram to illustrate how hybrids might change over time: Here is an example where there is reinforcement of barriers to reproduction in a hybrid zone between closely related species of European flycatchers: Page 512 The breakdown of reproductive barriers between species can be seen in this example of cichlid fish species in Lake Victoria: How fast does speciation take place? Is it a gradual process, or a very quick process followed by long periods of little change? This diagram illustrates these two possibilities: Here is an example in which a single gene change resulted in the development of a new species: In this example,an allele for flower colour was found to be influencing pollinators preference for certain species: Show how bread wheat species evolved from the following three ancestral species: Question: How do the major morphological transformations of macroevolution occur? Act 24.A 1. Evolutionary novelties can be modifications of older structures. See video at: http://www.pbs.org/wgbh/evolution/library/01/1/l_011_01.html 2. Exaptations - gradual modification of earlier structures for new functions. Act 24A