AP Biology
Chapter 17
Species and Their Formation
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OBJECTIVES
• Define the biological species concept.
• Describe some limitations of the biological species concept.
• Explain how gene flow between closely related species can be prevented.
• Distinguish between prezygotic and postzygotic isolating mechanisms.
• Describe 5 prezygotic isolating mechanisms and give an example of each.
• Distinguish between allopatric and sympatric speciation.
• Describe the role of geographical isolation in allopatric speciation.
• Explain how polyploidy can cause reproductive isolation in sympatric speciation.
• Describe the adaptive radiation model.
• Distinguish between gradualism and punctuated equilibrium models of speciation.
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|Definition of a Species |Definition and Possible Limitation |
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|Morphological Species Concept | |
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|The Biological Species Concept (Mayr) | |
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|Lineage Species | |
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Why is the biological species concept not applicable to asexual organisms?
What makes reproductive isolation the major prequistiee of speciation?
Modes of Speciation – Summarize EAch and Provide and Example
|Allopatric |Sympatric |
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How can polyploidy contribute to sympatric speciation in plants?
Once reproductive isolation is established, genetic diverage can occur, limiting the ability of species to interbreed. Summarize the types of reproductive isolating mechanisms below:
Reproductive Barriers
|Prezygotic: |
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Reproductive Barriers
|Postzygotic: |
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How are prezygotic reproductive barriers different from postzygotic barriers?
Complete the Applying the Concept Problems on pages 338 and 344.
Sample Problems
Use the key below to identify the type of reproductive barrier being described.
A. Habitat isolation B. Temporal isolation
C. Behavioral isolation D. Mechanical isolation
E. Gametic isolation
_________ Gametes fail to fuse
_________ Egg and sperm don’t recognize each other
_________ Differences in sexual or anatomical structures
_________ Mating dance of a male not recognized by a female
_________ Different mating seasons within a population
_________ Members of population separate by a mountain range
_________ Male flowers of some members of a plant species produce pollen before most of
the female flowers are open
_________ Variation in mating ritual not recognized by female
_________ Male reproductive organs in insect populations vary enormously in size and
shape, preventing the effective transfer of sperm to females of different species
_________ Structure of flower restricts access of insects without specific physical and
behavioral adaptations
Identify the type of reproductive barrier illustrated by the following examples and indicate whether they are pre- or postzygotic barriers.
|Example |Type of Barrier |Pre- or Post- |
|Two species of frogs are mated in the ab and produce viable, | | |
|but sterile, offspring | | |
|Two species of sea urchin release their gametes at the same | | |
|time, but cross-fertilization doe not occur | | |
|Two species of orchid have different length nectar tubes and | | |
|are pollinated by different species of moths | | |
|Two species of mayflies emerge during different weeks in | | |
|springtime | | |
|Two species of salamanders will mate in the lab and produce | | |
|viable, fertile offspring, but offspring of these hybrids are| | |
|sterile | | |
|Two similar species of birds have different mating rituals | | |
|When two species of mice are bred in the lab, embryos usually| | |
|abort | | |
|Peepers breed in woodland ponds, whereas leopard frogs breed | | |
|in swamps | | |
Match the term with the correct definition
A. Adaptive Radiation B. Allopatric speciation
C. Sympatric speciation
_________ New species arise when a population is segregated by geographic barrier
_________ Emergence of numerous species from a common ancestor that spreads into a
new environment
_________ New species arise within the range of the parent population
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