two categories of reproductive isolation

- prezygotic isolation and postzygotic isolation

- barriers to reproductive events that take place before fertilization - mechanisms include isolation by habitat, behavioral isolation, temporal isolation, mechanical isolation, and gametic isolation.

postzygotic isolation

- barriers to reproduction that occur after fertilization has taken place.

- Organisms that live in different habitats are much less likely to have contact with each other and mate. - Example: If some flies were attracted to apples and others attracted to pears, they would be separated by their habitats and less likely to mate.

- Courtship behaviors prior to mating can be species specific. If a courtship behavior is neither recognized nor desirable to an organism, it will not mate. - For example, if a male presents the wrong type of food to a female, she might not mate.

- Organisms that mate at different times or have different breeding seasons will not be able to mate together. - For example, the eastern and western spotted skunks do not interbreed because they have different mating seasons.

- If the reproductive organs do not fit between different populations, individuals will be unable to mate. - For example, male spiders have organs called pedipalps that deposit the sperm into the female. If the pedipalps don’t fit the female, the spiders will be unable to mate together.

- There must be biochemical recognition between the sperm and the egg. If the egg does not recognize certain chemical markers on the sperm, or if the sperm cannot penetrate the egg, fertilization will not occur.

Which of the following is not a prezygotic barrier to reproduction?

- The hybrid of two different species of the genus Anopheles is unable to reproduce successfully.

A species of fly only mates within a purple flower. One day, a fly is born with a mutation that makes a yellow flower more attractive, and he avoids the purple flower entirely. Which of the following scenarios describes (1) the necessary events for that mutation to persist in the population and (2) a possible outcome if the mutation does persist?

- Another fly must be born with a mutation that gives it a preference for yellow flowers. The fly must be female and mate with the original, yellow-flower-loving male. They will produce offspring that also are attracted to yellow flowers, and thus, the mutation will persist. Eventually, two groups of flies will arise: flies that mate only in purple flowers and flies that mate only in yellow flowers. Because the two populations are isolated based on their behavior, speciation occurs.

Speciation takes place relatively quickly within lineages in which species have complex behavior. The best explanation of this is that

- individuals within these species are much more discriminating in choosing potential mates

1.8.3 Prezygotic Reproductive Isolation Flashcards by Irina Soloshenko

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1.8.3 Prezygotic Reproductive Isolation Flashcards

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