“Nothing in biology makes sense except in light of evolution” -Theodosius Dobzansky

1. “Nothing in biology makes sense except in light of evolution” -Theodosius Dobzansky

2. “Nothing in biology makes sense except in light of evolution” • Viewed evolution as "a change in the frequency of an allelewithin agene pool“ • His Idea: that it is through mutations in genes that natural selection takes place. Theodosius Dobzansky

3. The History of Evolutionary Thought

4. Aristotle (384-322 B.C.) • Ladder of Life • 2 types of animals – those w/ blood & those w/o • Animals classified by their way of life • Plants by structure • Observation of various marine life anatomy was remarkably accurate • Distinguished whales from dolphins

5. Carol von Linné (1707 – 1778) “Father of Taxonomy” • Linnaeus was classifying organisms based on what they looked like. • This made it difficult to classify organisms that seemed to share characteristics with both kingdoms that Linnaeus proposed, Plants and Animals. • For example, fungi including mold and mushrooms do not move (or do they?) so they seem to be plants but, unlike plants…..?????

6. Taxons of Classification

7. Immutable Species???

8. Classifying organisms often starts at the cellular level Autotrophic ?? Heterotrophic??? Motility? Cell wall composition Nuclei?? Membrane-bound Organelles???

9. Cladistics (phylogeny) A system of classification based on the study of evolutionary relationships history of groups of organisms.

11. Primate Evolution

12. Cladogram

13. An Example of Cladogram Construction for Vertebrates

14. Georges-Louis Buffon (1707-1788) • Buffon questions a 2,000 yr. dogma 100 yrs. before Darwin • Openly suggests the earth is older than 6,000 years • Supported a concept similar to Lyell’s uniformitarianism • Multiple Centers of Creation

15. Jean-Baptiste Lamarck (1744-1829) • His name is associated merely w/ a discredited theory of heredity – he died in obscurity & poverty • Darwin & Lyell give him great credit • Law of use/disuse • Law of acquired characteristics

16. LAMARCK’S THEORY

17. ACCORDING TO DARWIN…

18. Thomas Malthus (1766-1834) • 1798 wrote “Essay on the Principle of Population” • Humans have the tendency to outgrow their food supply • Forces that work against this, war, famine, and disease • Darwin read essay and thought this reasoning applied more strongly to animals and plants

19. Sir Charles Lyell (1797-1875) • British geologist • Wrote Principles of Geology • Showed that the earth was very old and changed its form slowly (i.e. erosion) • Dated the age of rocks by using fossils embedded in stone as time indicators

20. How Lyell’s work helped Darwin • Darwin witnessed volcanic eruptions • Darwin witnessed an earthquake that raised a rocky shoreline 3m above its original position • Noted fossils of marine life many feet above sea level

21. This understanding of geology influenced Darwin in 2 ways: • First, Darwin asked himself: If the Earth could change over time, might life change as well? • Second, he realized that it would have taken many, many years for life to change in the way he suggested. This would have been possible only if the Earth were extremely old

22. James Hutton (1726-1797) • Layers of rock are moved by forces beneath the earth’s surface • Proposed the earth had to be much older than a few thousand years

23. Hutton’s Theory of Geological Change • Some rocks twist and bend • Others are buried and others are pushed up from the sea floor • Resulting rocks are shaped by natural forces • These processes operate extremely slowly over the course of millions of years

24. Alfred Wallace (1823-1913) • Studied the way geography limited or facilitated the extension of species range • How ecology influenced the shaping of adaptations • In 1858, shared with Darwin on the Theory of Evolution by means of Natural Selection

25. Charles Darwin (1809-1882) • Voyaged around the world 1831-1836 • Wrote On the Origin of Species which reveals his ideas on Evolution by means of Natural Selection

26. Natural Selection Summarized: Darwin’s theory suggests that in a species: • There is a tendency towards overproduction • Variationexists • Variations are inherited • Individuals survive in their environments with varying degrees of success • Best adapted, survive and pass favorable variation on to next generation • In time, great differences arise, until a new species evolved from an old species

27. Biological Fitness

28. What is biological fitness???

29. Survival of the Fittest…. • Fitness - the genetic contribution of an individual to succeeding generations relative to the contributions of other individuals in the population

30. Adaptive Radiation – The emergence of new species from common ancestor can occur if the ancestor was introduced into an environment that offered a diversity of new opportunities and problems.

32. Coevolution: Mutual evolutionary influence between two species • Typically evolution of two species totally dependent on each other. • Exert selective pressure on the other, so they evolve together. • Extreme example of mutualism.

33. Homologous Structures • Structures that have different mature forms in different organisms but develop from the same embryonic tissues.

34. Homologous Structures

35. Convergent Evolution . • A kind of evolution wherein organisms evolve structures that have similar structures or functions in spite of their evolutionary ancestors being very dissimilar or unrelated. • These structures are referred to as analogous.

36. Comparative Embryology (used for classifying organisms)

37. Human embryo 4 weeks

38. Vestigial Structures

39. Vestigial Structures Vestigial hind limbs in adult whale Hind limb bud in whale embryo

40. Eye bulbs of Blind cave salamander Anthers & pollen grain Of asexual dandelion More Vestigial Structures

41. Evolutionary trade-off for a Big Brain Shoulder lodged on pubic bone Narrow Pelvic Opening

42. Photo: John Weinstein/The Field Museum