The History of Evolutionary Thought

1. The History of Evolutionary Thought

2. 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

3. 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

4. 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

5. LAMARCK’S THEORY

6. ACCORDING TO DARWIN…

7. 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

8. 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

9. 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…..?????

10. Taxons of Classification

11. Immutable Species???

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

13. Homologous Structures

14. Convergent Evolution A kind of evolution wherein organisms evolve structures that have similar (analogous) structures or functions in spite of their evolutionary ancestors being very dissimilar or unrelated.

15. Comparative Embryology Can be used to classify organisms

16. Vestigial Structures – due to evolution ,structures in an organism that have reduced or no function Vestigial hind limbs in adult whale Hind limb bud in whale embryo

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

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

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

20. Cladogram

21. An Example of Cladogram Construction for Vertebrates

23. Adaptive radiation

24. Adaptive radiation

25. 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.

26. What is biological fitness???

27. Biological fitness: The contribution an individual makes to the gene pool of the next generation relative to contributions of other individuals Offspring should be fertile

28. 1stPhylogenetic Tree

29. Bird Tree of Evolution

30. Evolution of Populations

31. Populations are the units of evolution

32. Population • A group of individuals of the same species living in the same place at the same time.

33. Biological definition of a species • A group of populations whose members are capable of interbreeding and producing fertile offspring.

34. Population genetics An important turning point for evolutionary theory the 1920’s. Developed in the 1920’s A field that combines Darwin’s and Mendel’s ideas by studying how populations change over time.

35. The Gene Pool • In studying evolution at the population level, geneticists focus on the GP • Total collection of genes in a population at any one time.

36. The Gene Pool

37. Sources of Genetic Variation • Mutations • Gene Shuffling • Crossing over • Sexual reproduction

38. Single Gene Traits • The number of phenotypes produced for a given trait depends on how many genes control the trait

39. Polygenic traits are controlled by two or more genes

40. Natural Selection can affect the distributions of phenotypes in 3 ways: • Directional selection • Disruptive selection • Stabilizing selection

41. Directional Selection • When individuals at one end of the curve have higher fitness than individuals in the middle or at the other end.

42. Disruptive Selection • When individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle.

43. Stabilizing Selection • Takes place when individuals near the center of a curve have higher fitness than individuals at either end

44. Isolating Mechanisms Behavioral Geographic Temporal The Process of Speciation

45. Behavioral

46. Geographical

47. Temporal

49. The Hardy–Weinberg principle states: • Both allele and genotype frequencies in a population remain constant or are in equilibriumfrom generation to generation unless… • Disturbing influences happen such as non-random mating, mutations, selection, limited population size, random genetic drift and gene flow. • Genetic equilibrium is a basic principle of population genetics.

50. Hardy-Weinbergprinciple is like a Punnett square for populations, instead of individuals.