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Understanding Species: Creation and Extinction in Macroevolution

Explore how new species are created and why old species become extinct in macroevolution. Learn about reproductive barriers, speciation processes, patterns of evolution, and the role of natural selection. Discover the fascinating concepts of convergent evolution, divergent evolution, coevolution, and the impact of extinction events.

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Understanding Species: Creation and Extinction in Macroevolution

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  1. MACROEVOLUTION involves evolution at the large scale as species originate, adapt to their environment, and possibly become extinct. How do we create new species? How do old species become extinct?

  2. What is a species? • A group of organisms that interbreed with each other and share the same gene pool. • A group of organisms that produce fertile offspring. *Simplified: A species is a group of organisms that can have children. Also their children can have children.

  3. Each species is reproductively isolated from every other species, meaning that organisms of different species can not produce offspring. Reproductive barriers can be PREZYGOTIC or POSTZYGOTIC.

  4. There are several types of PREZYGOTIC BARRIERS Prezygotic isolating mechanisms prevent reproduction and make fertilization unlikely • geographic isolation • Gamete isolation • temporal isolation • behavioral isolation • mechanical isolation

  5. Geographic Isolation • Organisms can not mate because they are separated by geographic barriers. Temporal Isolation • Organisms can not mate because they reproduce in different seasons or different times of day.

  6. Behavioral Isolation • Organisms don’t mate because they have different mating rituals. Mechanical Isolation • Organisms can not mate because their genitalia is unsuitable for one another.

  7. Gamete Isolation • Organisms can not mate because their sperm and egg will not fuse.

  8. There are several types of Postzygotic Isolating mechanisms. Postzygotic Isolating Mechanisms take place once organisms have mated. • Zygote mortality • Hybrid Sterility • Hybrid Inviability

  9. Hybrid Sterility • A hybrid offspring is produced, but is sterile.

  10. Hybrid Inviability • The offspring survives, but is weak and sickly. Zygote Mortality • Fertilization occurs, but the zygote does not survive.

  11. There are various types of speciation, or ways to create new species. • ALLOPATRIC SPECIATION • SYMPATRIC SPECIATION • ADAPTIVE RADIATION

  12. In ALLOPATRIC SPECIATION, an ancestral population is geographically isolated, resulting in the evolution of separate species. • Populations begin to diverge when gene flow between them is restricted and variations accumulate until the populations are reproductively isolated.

  13. In SYMPATRIC SPECIATION, an ancestral population is isolated, resulting in the evolution of separate species. • Sympatric speciation involves speciation without a geographic barrier.

  14. Adaptive radiation involves the evolution of several new species from an ancestral species. • Adaptive radiation occurs as natural selection drives members of the ancestral species to adapt to several different environments.

  15. Patterns of Evolution • Evolution through Natural Selection is not random. Although mutations and Genetic Drift can not be predicted and are random themselves, Natural Selection acting upon these changes is not random at all…….the best suited for their environment are still the ones most likely to survive and reproduce. How the actual “Evolution” takes place is up for some debate.

  16. Patterns of Evolution • Convergent Evolution…..Unrelated species growing more and more alike due to adapting to their surroundings….Analogous Structures is an example of Convergent Evolution • Divergent Evolution ……When closely related species grow less and less alike due to adapting to their surroundings….ie) Darwin's Finches

  17. Patterns of Evolution • Coevolution ….When two or more species evolve in response to changes in the other. • Extinction ….The elimination of a species on Earth….happens when a species is unable to adapt to its surroundings

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