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Darwinian Evolution

Darwinian Evolution. Chapter 10 10.2 - 10.5. Galapagos Islands . Darwin visited the Galapagos Islands He formed his ideas about natural selection here Why were the Galapagos Islands a good place to study natural patterns?

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Darwinian Evolution

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  1. Darwinian Evolution Chapter 10 10.2 - 10.5

  2. Galapagos Islands • Darwin visited the Galapagos Islands • He formed his ideas about natural selection here • Why were the Galapagos Islands a good place to study natural patterns? • Variation – difference in physical traits of an individual from those of the other members in the group • Darwin took note of the variation of organisms via each island in the Galapagos

  3. Different environments • Long necked and legged tortoises lived in areas with mostly tall plants. • Tortoises with a short neck and legs, lived in areas with short plants and mosses. • Animals could adapt to their environment?

  4. Adaptation • Adaptation – feature that allows an organism to better survive in its environment • Adaptations can lead to a genetic change in a population over time • Evolution – genetic change in a population over time • So adaptations can lead to ______ ?

  5. Ancient Earth? • Darwin found fossil evidence of ancient & extinct organisms that were similar but different than currently living (extant) forms.

  6. 10.3 – How does Evolution occur?

  7. Selection • Darwin observed that domesticated plants and animals displayed variation that was not found in their wild counterparts • Through selection of animals with particular traits, breeders could produce a great amount of diversity • Artificial selection – humans select for certain traits, and preferentially breed those animals in possession of those traits • Called artificial selection since humans are selecting for certain traits that they deem desirable

  8. Heritability • In order for a trait to be selected for, artificial or natural, trait must be inherited • Heritability – the ability of a trait to be passed down from one generation to the next

  9. Natural Selection • Natural Selection – mechanism by which individuals that have inherited favorable adaptations produce MORE offspring on average than do other individuals • Environment is the selective agent • Characters are selected only if they confer some advantage to those who have it

  10. Conditions for Natural Selection • Struggle for survival • Resources are limited • Space, food, mating opportunities • Wants are Unlimited • Organisms can produce more offspring than the environment can provide for • Certain adaptations seemed well-suited for their environment

  11. 4 Principles for Theory of Natural Selection • 1. Variation • the heritable differences are the basis for natural selection • 2. Overpopulation • If the population is supported by the environment, no selection will occur • 3. Adaptation • Certain individuals have favorable variation that enables them to be better suited to their environment • 4. Descent with Modification • Natural selection will result in populations that are better suited to survival and reproduction in an environment

  12. ADAPTATION VARIATION OVERPRODUCTION

  13. Imperfect Organisms • Why are organisms not perfectly adapted to their environment? • Natural selection works on EXISTING variation • Natural selection can only modify what is there, so perfect structures are not always possible • Could a human ever be able to lift 18 tons (36,000 pounds)? • Could a human ever be able to develop gills for underwater existence?

  14. Evidence for Evolution • Fossils • Okay • Biogeography • Good • Embryology • Excellent • Anatomy • Excellent • Genomics

  15. Fossils in older layers are more primitive than those in the upper layers. Fossils provide evidence of evolution.

  16. island species most closely resemble nearest mainland species • populations can show variation from one island to another The study of geography provides evidence of evolution.

  17. Larva Adultbarnacle Adult crab • identical larvae, different adult body forms • similar embryos, diverse organisms Embryology provides evidence of evolution.

  18. Molefoot Batwing Human hand • Homologous structures are similar in structure but different in function. • Homologous structures are evidence of a common ancestor. The study of anatomy provides evidence of evolution.

  19. Human hand Mole foot Bat wing Fly wing • Analogous structures have a similar function. Analogous structures are not evidence of a common ancestor.

  20. Vestigial Structures • Vestigial structures are remnants of organs or structures that had a function in an early ancestor. • Ostrich wings are examples of vestigial structures.

  21. Paleontology provides evidence to support evolution.

  22. Molecular and genetic evidence support fossil and anatomical evidence. • Two closely-related organisms will have similar DNA sequences.

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