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Understanding Evolution: Charles Darwin's Theory of Natural Selection and Adaptation

This overview explores the fundamentals of evolution as proposed by Charles Darwin, focusing on his theory of natural selection. Darwin's journey on the S.S. Beagle led him to hypothesize that variations among species drive their ability to adapt and survive in specific environments. Key concepts include the importance of genetic variations, adaptations, and the role of both natural and artificial selection. Direct evidence for evolution is discussed, including fossils, homologous and analogous structures, and vestigial traits.

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Understanding Evolution: Charles Darwin's Theory of Natural Selection and Adaptation

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  1. So what does evolution mean? Well, The Book Says:

  2. Charles Darwin

  3. Charles Darwin • Took a trip on the S.S. Beagle to the Galapagos Islands to work as a naturalist. • Hypothesized that Natural Selection drove evolution in his book, On the Origin of Species. • He invented the concept- Survival of the fittest- which actually means survival of the slightly better suited to a particular environment at a particular time

  4. Darwin’s Theory : Natural Selection • Environment limits growth of populations • Due to variations among individuals in a species, some members of a population compete better for limited resources, so they survive and reproduce, while others do not.

  5. VARIATIONS • Differences in a species • Raw material for evolution • Caused by: 1) Crossing over 2)Chance Assortment 3)Mutation ADAPTATIONS: Variations that improve chances for survival!

  6. Notice The Variation In These Individuals Of A House Finch Population Some are more likely to survive and/or mate due to differences in coloration

  7. Adaptations • A variation that continues to exist generation after generation and increases the organisms chance to survive and reproduce (pass on its genes)

  8. ADAPTATIONS • Physical • Chemical • Behavioral • MORPHOLOGICAL • CHEMICAL • BEHAVIORAL

  9. Physical ADAPTATION

  10. Physiological ADAPTATION

  11. BEHAVIORAL ADAPTATION

  12. ADAPTATION • morphological? • Chemical? • Behavioral?

  13. Artificial Selection • Selecting and Breeding the organisms with the most desirible traits. • Can you think how humans do this?

  14. Dog Breeding

  15. Horse Breeding

  16. Natural Selection • Darwin thought that there must be a force in nature that worked like artificial selection. • That force came to be known as Natural Selection, the basis for evolution.

  17. Individuals struggle to survive • Competition for food (plants) • Escaping from predators • Finding Mates • Locating Shelter

  18. Natural Selection http://www.nmsu.edu/~molbio/dog/nature.htm

  19. Direct Evidence for Evolution • Mimicry – Structural Adaptation evolved in some species where one species resembles another. • Camouflage – Structural adaptation that enables a species to blend with their surroundings • Bacterial resistance

  20. Mimicry

  21. Mimicry

  22. Mimicry Fly Hornet

  23. Camouflage

  24. Camouflage

  25. Why does this frog have funky skin?

  26. Why does this fish have a large dot on its back?

  27. Bacteria (Direct Evidence)

  28. Evidence Of Evolution • Fossils • Homologous Structures • Analogous Structures • Vestigial Structures • Embryological Similarities • Macromolecule (DNA, RNA, Proteins) Similarities

  29. Fossils

  30. Fossils

  31. Camels

  32. Homologous Structures • Structures with common evolutionary origins. Can be similar in arrangement, function, or both.

  33. Analogous Structures • Show that the environment selects for certain abilities. • Structures that do not have a common evolutionary origin but are similar in function

  34. Analagous Structures

  35. Vestigial Structures • Body structure that has no function in a present day organism but was probably useful to an ancestor.

  36. Vestigial Structures

  37. Vestigial Structures

  38. Vestigial Structures Human Vestigial Structures

  39. Embryology

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