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Evolution by Natural Selection

Evolution by Natural Selection. LaMarck. Organisms adapted to their environments by acquiring traits change in their life time Disuse organisms lost parts because they did not use them — like the missing eyes & digestive system of the tapeworm

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Evolution by Natural Selection

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  1. Evolutionby Natural Selection

  2. LaMarck • Organisms adapted to their environments by acquiring traits • change in their life time • Disuseorganisms lost parts because they did not use them — like the missing eyes & digestive system of the tapeworm • Perfection with Use & Needthe constant use of an organ leads that organ to increase in size — like the muscles of a blacksmith or the large ears of a night-flying bat • transmit acquired characteristics to next generation

  3. Charles Darwin • 1809-1882sh naturalist • Proposed the idea of evolution by natural selection • Collected clear evidence to support his ideas

  4. Thinking of natural selection Tell your partner the 4 conditions required for natural selection to occur. Remember VIES? 1.Variation 2. Inheritance 3. Environmental population limits 4. Selection

  5. LaMarckian vs. Darwinian view • LaMarck • in reaching higher vegetation giraffes stretch their necks & transmits the acquired longer neck to offspring • Darwin • giraffes born with longer necks survive better & leave more offspring who inherit their long necks

  6. Voyage of the HMS Beagle • Invited to travel around the world • 1831-1836 (22 years old!) • makes many observations of nature • main mission of the Beagle was to chart South American coastline Robert Fitzroy

  7. Voyage of the HMS Beagle • Stopped in Galapagos Islands • 500 miles off coast of Ecuador

  8. Unique species

  9. Darwin found… birds Collected many different birds on the Galapagos Islands. Thought he found very different kinds… Finch? Sparrow? Warbler? Woodpecker?

  10. But Darwin found… a lot of finches Darwin was amazed to find out: All 14 species of birds were finches… But there is only one species of finch on the mainland! Large Ground Finch Small Ground Finch Finch? Sparrow? Warbler Finch Veg. Tree Finch Warbler? Woodpecker?

  11. Tree Thinking Descendantspecies Ancestralspecies Large-seed eater? Large GroundFinch Small-seed eater? Small GroundFinch Warbler? Leaf-browser? Veg. Tree Finch Warbler Finch

  12. Correlation of species to food source Seedeaters Flowereaters Insecteaters Adaptive radiation

  13. Darwin’s finches • Differences in beaks • associated with eating different foods • survival & reproduction of beneficial adaptations to foods available on islands Warbler finch Cactus finch Woodpecker finch Sharp-beaked finch Small insectivorous tree finch Small ground finch Warbler finch Large insectivorous tree finch Cactus eater Mediumground finch Tree finches Ground finches Insect eaters Seed eaters Vegetarian tree finch Large ground finch Bud eater

  14. Darwin’s finches • Darwin’s conclusions • small populations of original South American finches landed on islands • variation in beaks enabled individuals to gather food successfully in the different environments • over many generations, the populations of finches changed anatomically & behaviorally • accumulation of advantageous traits in population • emergence of different species

  15. 5 pieces of evidence for evolution show ways similarities are observed…

  16. 1. Homologous structures- Similar anatomical features that originated in a shared ancestor. • (NOT analogous structures- features that have identical functions but different internal anatomy and different development in the embryo)

  17. Analogous structures • Separate evolution of structures • similar function and similar external form • different internal structure & development • different origin Solving a similar problem with a similar solution

  18. 2. Vestigial Structures • Modern animals may have structures that serve little or no function • remnants of structures that were functional in ancestral species • deleterious mutations accumulate in genes for non-critical structures without reducing fitness • snakes & whales — remains of pelvis & leg bones of walking ancestors • eyes on blind cave fish • human tail bone

  19. Vestigial Structures • Hind leg bones on whale fossils

  20. 3. Comparative embryology • Similar embryological development in closely related species • all vertebrate embryos have similar structures at different stages of development • gill pouch in fish, frog, snake, birds, human, etc.

  21. 4. Paleontology - Fossil Record • Layers of sedimentary rock contain fossils • new layers cover older ones, creating a record over time • fossils within layers show that a succession of organisms have populated Earth throughout a long period of time

  22. Fossil record • A record showing us that organisms descended from ancestral species

  23. Nigersaurus

  24. Nigersaurus

  25. Comparitive morphology

  26. Geology

  27. 4. Biogeography • Closely related species tend to be found in the same geographic region, whereas the same ecological niches in distant regions are occupied by very different species. • Mammals on separated landmasses followed different evolutionary patterns.

  28. Parallel Evolution • Convergent evolution in common niches • filling similar ecological roles in similar environments, so similar adaptations were selected • but are not closely related marsupial mammals placental mammals

  29. 5. Biochemistry in living organisms • All use DNA (or RNA) as their genetic material. • All use the same universal genetic code. • All use the same amino acids in their proteins. These similarities suggest that organisms have evolved from a common ancestor that had these characteristics.

  30. Human/kangaroo 100 Human/ cow Dog/ cow 75 Rabbit/ rodent Human/rodent Llama/ cow Horse/ donkey 50 Nucleotide substitutions Horse/cow Sheep/ goat Pig/ cow 25 Goat/cow 0 0 25 50 75 100 125 Millions of years ago Molecular record • Comparing DNA & protein structure • universal genetic code! • DNA & RNA • compare common genes • cytochrome C (respiration) • hemoglobin (gas exchange) Closely related species have sequences that are more similar than distantly related species • DNA & proteins are a molecular record of evolutionary relationships

  31. Phylogeny • The study of the evolutionary history of groups of organisms is called phylogeny. • Two useful approaches in phylogeny: • Study of the fossil record • Comparison of molecular structures.

  32. Comparative hemoglobin structure Dog Human Macaque Bird Frog Lamprey 8 32 45 125 67 0 10 20 30 40 50 60 70 80 90 100 110 120 Number of amino acid differences between hemoglobin (146 aa) of vertebrate species and that of humans

  33. Macromolecules- comparing DNA and protein sequences

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