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Chapter 15

Chapter 15. 15-3 Darwin Presents His Case. Natural Variation Differences among individuals Artificial Selection Selection by humans for breeding of useful traits from the individual variation among different organisms. Struggle for existence

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Chapter 15

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  1. Chapter 15 15-3 Darwin Presents His Case

  2. Natural Variation • Differences among individuals • Artificial Selection • Selection by humans for breeding of useful traits from the individual variation among different organisms.

  3. Struggle for existence • Competition among members of a species for food, living spaces and the other necessities of life • Fitness • Ability of an organism to survive and reproduce in its environment

  4. Vocabulary • Natural Variation- • Differences among individuals of a species • Artificial Selection • Selection by humans for breeding of useful traits from the natural variation among different organisms.

  5. Vocabulary • Struggle for existence- • Competition among members of a species for food, living space, and the other necessities of life. • Fitness- • Ability of an organism to survive and reproduce in its environment.

  6. Vocabulary • Adaptation • Inherited characteristic that increases an organism’s chance of survival. • Survival of the fittest- • Process by which individuals that are better suited to their environment survive and reproduce most successfully; also called natural selection.

  7. Vocabulary • Natural Selection- • See survival of the fittest • Descent with Modification • Principle that each living species has descended, with changes from other species over time.

  8. Vocabulary • Common descent- • Principle that all living things have a common ancestor • Homologous structure • Structures that have different mature forms in different organisms but develop from the same embryonic tissues

  9. Vocabulary • Vestigial organ • Organ that serves no useful function in an organism.

  10. 15-3 Darwin Presents His Case • Natural Variation and Artificial Selection

  11. 15-3 Darwin Presents His Case 1. Natural Variation: differences among individuals of a species found in all types of organisms a. Nature (including people): Example • Farm Crops: Example • Livestock: Example

  12. 15-3 Darwin Presents His Case 2. Artificial Selection: nature provided the variation among different organisms, and humans selected those variations that they found useful • Plants: Example • Animals: Example

  13. 15-3 Darwin Presents His Case B. Evolution by Natural Selection 1. Struggle for existence: members of each species compete regularly to obtain food, living space, and other necessities of life 2. Survival of the Fittest a. Fitness: the ability of an individual to survive and reproduce in its specific environment b. Adaptation: any inherited characteristic that increases an organism’s chance of survival c. Survival of the fittest: the process where individuals that are better suited to their environment survive and reproduce most successfully

  14. 15-3 Darwin Presents His Case 3. Natural Selection: selection that is not controlled by humans a. Over time there are changes in the inherited characteristics of a population b. Changes increase a species’ fitness in its environment

  15. 15-3 Darwin Presents His Case C. Evidence of Evolution 1. Darwin argued that living things have been evolving on Earth for millions of years 2. Evidence could be found in four areas: a. The Fossil Record b. Geographic Distribution of Living Species c. Homologous Body Structures d. Similarities in Early Development

  16. 15-3 Darwin Presents His Case

  17. 15-3 Darwin Presents His Case

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