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Understanding Natural Selection in Evolutionary Biology

Explore the concept of natural selection in organisms and its role in evolution. Learn about different types of selection processes such as stabilizing, directional, and disruptive selection. Understand how natural selection leads to speciation and resistance in populations.

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Understanding Natural Selection in Evolutionary Biology

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  1. Natural Selection (15.3) State Standard SB5D. Relate natural selection to changes in organisms

  2. Evolution Chapter 15 15.3 Natural Selection-Speciation-Resistance Natural Selection • Nature acts to select the individuals that are best adapted for survival and reproduction in a particular environment

  3. Evolution Chapter 15 Principles of Natural Selection Natural selection takes place when… • Individuals in the population show variations. • The variations are inheritable. • Members of the population have more offspring than can survive on available resources (overproduction). • Variations that increase reproductive success have a greater chance of being passed on.

  4. 15.3 Natural Selection-Speciation-Resistance • Industrialization & the peppered moths

  5. Evolution Chapter 15 15.3 Natural Selection-Speciation-Resistance • Stabilizing selectionoperates to eliminateextreme expressions of a traitwhen the average expression leads to higher fitness. Ex: Peppered Moths before the Industrial Revolution

  6. Evolution Chapter 15 15.3 Natural Selection-Speciation-Resistance • Directional selectionmakes an organism more fit by selecting against one extreme. Ex: Pollution from the Industrial Revolution caused directional selection in the peppered moths.

  7. Evolution Chapter 15 15.3 Natural Selection-Speciation-Resistance • Disruptive selection is a process that splits a population into two groups. Ex: Different rock types in the same biome will favor different coat varieties of these mice

  8. Evolution Chapter 15 15.3 Natural Selection-Speciation-Resistance • Sexual selection operates in populations where males and females differ significantly in appearance. • Qualities of sexual attractiveness appear to be the opposite of qualities that might enhance survival.

  9. Evolution • Can occur in a relatively short time when one species gives rise to many different species in response to the creation of new habitat or some other ecological opportunity Chapter 15 15.3 Natural Selection-Speciation-Resistance Adaptive Radiation – AKA Divergent Evolution/Speciation

  10. Evolution Chapter 15 15.3 Natural Selection-Speciation-Resistance Coevolution • The relationship between two species might be so close that the evolution of one species affects the evolution of the other species. • Associated with mutualism

  11. Evolution Chapter 15 15.3 Natural Selection-Speciation-Resistance Convergent Evolution • Unrelated species evolve similar traits because of similar environmental pressures.

  12. Evolution Chapter 15 15.3 Natural Selection-Speciation-Resistance Rate of Speciation • Evolution proceeds in small, gradual steps according to a theory called gradualism. • Punctuated equilibriumexplains rapid spurts of genetic change causing species to diverge quickly.

  13. Evolution Chapter 15 15.3 Natural Selection-Speciation-Resistance

  14. Evolution A B C D Chapter 15 FQ 14 15.3 Formative Questions Which evolutionary pattern is represented by the similarities between these two organisms that live on separate continents? coevolution convergent evolution directional evolution divergent evolution

  15. Evolution A B C D Chapter 15 CAQ 2 Chapter Assessment Questions The divergent evolution of these cichlid fish is an example of what type of speciation? coevolution mutation adaptive radiation convergent evolution

  16. Evolution A B C D Chapter 15 CAQ 3 Chapter Assessment Questions What tempo of evolution does this model represent? gradual elevated sequential punctuated

  17. Evolution A B C Chapter 15 STP 5 Standardized Test Practice Within a population of squirrels, those that live higher in the mountains where it is cooler have long fur. Squirrels that live in the foothills where it is warmer have short fur. The original population is believed to have had intermediate fur length. Which graph represents this type of natural selection?

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