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Evolution

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Evolution

  1. 1. Evolution An Introduction
  2. 2. Evolution vs. Creationism Here are a few websites you can look at to inquire further into the arguments for both creationism and evolution.  Creationism  http://www.talkorigins.org/faqs/wic.html  http://www.creationism.org/  Evolution (and creationism)  http://www.talkorigins.org/origins/faqs-mustread.html  http://www.bcholmes.org/wicca/evolution.html
  3. 3. The Origin of Life What the heck happened?
  4. 4. BANG!!!!!!!!!
  5. 5. The Universe Big Bang Theory  15 bya  Things cooled  Atoms formed  Planets, stars and solar systems formed More on the Big Bang Theory  http://www.umich.edu/~gs265/bigbang.htm
  6. 6. The Earth About 4.5 bya Formed from collecting dust, gases, etc. Atmosphere of CO2, H2O, N2, CO and NH3 Earth cools  Liquid water – needed for life  3.8 bya More information  http://mediatheek.thinkquest.nl/~ll125/en/bigbang.h
  7. 7. First Organic Compounds H2 + CH4 + NH3 + heat + lightening = simple organic compounds  Amino acids  Monosaccharides Miller and Urey (1950’s)  Tested Oparin’s hypothesis Meteorites? More information  http://www.chem.duke.edu/~jds/cruise_chem/Exobiolo gy/miller.html
  8. 8. First Cell-like StructuresProtobionts Microspheres  Proteins organized as a membrane Coacervates  Droplets of organic compounds So what?  Life-like  Grow in size  Take in substances from surroundings  Bud in two (reproduce)  Catalyze reactions  Maintain membrane potential  Spontaneous  Could lead to first cells
  9. 9. First “Cells” RNA considered key  Many forms  Simpler than DNA  Ribozymes  RNA can act as an enzyme!!!!  Mechanism for self-replication Maybe . . .  Self-replicating RNA ended up inside a coacervate or microsphere creating first cell- like structure
  10. 10. First Prokaryotes 3.5 bya Very simple single-celled organisms Similar to some of today’s prokaryotes Chemoautotrophs first  Break down inorganic compounds for energy  Archaebacteria Photoautotrophs evolve  Create oxygen  Changed everything
  11. 11. Prokaryote → Eukaryote
  12. 12. First Eukaryotes
  13. 13. Theories and Evidence
  14. 14. Definition of Evolution The processes that have transformed life on Earth from its earliest forms to the vast diversity that characterizes it today Mechanism for Evolution  Natural Selection Two types of evolution  Intraspecies  Single species evolves  Interspecies  New species evolves
  15. 15. Historical Context Aristotle For 2000 years -- species are perfect, they don’t evolve Religion  Creationism – same idea, God created all life Most Scientists (1700’s)  Natural Theology dominated – again, same idea Lamarck (1809)  Organisms evolve from ancestors-(1 st to say)  Use and disuse  Acquired characteristics Darwin (1859)  “The Origin of Species”  Few people held similar beliefs at that time
  16. 16. The Voyage of the Beagle Darwin’s observations  One – Species fertility = exponential growth  Two – Populations generally stable  Three – Resources limited  Leads to competition  Four – Individuals vary  Five – Much of this variation is heritable  If variation is beneficial, variation will flourish (lots)
  17. 17. Darwin’s Conclusion Evolution through adaptation due to natural selection i.e. Some individuals (because of variation) in a population will have better success at surviving and reproducing; therefore, the heritable traits of those organisms will be passed on while the heritable characteristics of less successful individuals will not.
  18. 18. Darwin’s Overall View Unity in life – all organisms relate back to an unknown original ancestor New species arise through evolution Depicted by a phylogenetic tree  Shows evolutionary history
  19. 19. A Phylogenetic Tree
  20. 20. “The Origin of Species" Two main points  States the occurrence of evolution (descent with modification)  Natural selection is the mechanism for evolution
  21. 21. Things to Note A population is the smallest unit that can evolve (a population is a group of interbreeding individuals belonging to a particular species in a given geographical area). Only heritable characteristics can be amplified or diminished through natural selection Generally, natural selection leads to evolution slowly over a long period of time.
  22. 22. EVIDENCE OF EVOLUTION One – BIOGEOGRAPHY  Geographical distribution of species  Example  Kangaroo  Armadillo  Question: Why are tropical animals of South America more closely related to species of South American deserts than to species of the African tropics?
  23. 23. EVIDENCE OF EVOLUTION Two – FOSSIL EVIDENCE  Fossil age can be determined through radioactive dating  Similarities in anatomy/morphology can be compared between fossils and similar extant organisms  Often supports and is supported by other evidence.
  24. 24. EVIDENCE OF EVOLUTION Three – COMPARATIVE ANATOMY  Homologous Structures  Vertebrate forelimbs  Vestigial Structures  Tailbone in humans  Pelvic bones, hind legs of whales
  25. 25. Human Vestigial Structures
  26. 26. EVIDENCE OF EVOLUTION Four – COMPARATIVE EMBRYOLOGY  A study of embryos and how they develop.  Closely related organisms go through similar stages of embryonic development.  Example  All vertebrates (birds, snakes, mammals, fish, frogs) go through an embryonic stage where they have gill pouches on the sides of their throats  Figure 15-9, page 291
  27. 27. EVIDENCE OF EVOLUTION Five – MOLECULAR BIOLOGY  compare amino acid sequences of proteins  compare DNA/RNA  Mitochondrial, ribosomal  All organisms have nucleic acids made up of the same kinds of molecules, universal!!!  Humans and even the simplest prokaryotes share some genes/proteins in common.  Example – Cytochrome C, a protein involved in aerobic respiration. NOTE: very similar DNA = very closely related
  28. 28. Direct Evidence of IntraspeciesEvolution Selective breeding in animals Selective breeding in plants, especially crops Guppies (Poecilia reticulata) of South America and Trinidad  http://www.pbs.org/wgbh/evolution/sex/guppy/low_bandwidth.html
  29. 29. Patterns of Evolution
  30. 30. COEVOLUTION Species closely associated with each other evolve together Example  Long-nosed fruit bat and the flowers on which they feed
  31. 31. CONVERGENT EVOLUTION Distantly related species evolve in similar ways due to similar environment. Example – Sharks and Porpoises  Morphologies are adapted to life in the water and are very similar.  Analogous structures are associated w/ convergent evolution
  32. 32. DIVERGENT EVOLUTION Closely related species become more and more dissimilar  Can result in a new species  ADAPTIVE RADIATION  Many related species evolve from a single ancestor  Galapagos Finches – likely related to food  ARTIFICIAL SELECTION (selective breeding)  Domesticated dogs
  33. 33. Genetic Equilibrium Population Genetics  Study of evolution from a genetic point of view, i.e. traits  POPULATION-smallest unit which may evolve Bell curves  When graphed, many traits within a species take on the shape  Indicates high # of individuals in the middle (average) with fewer #’s at either extreme (high or low) for a given trait.  Many polygenic, quantitative traits show this type of distribution
  34. 34. Genetic Equilibrium Punnett’s square’s allow genotype and phenotype predictions for a new generation of offspring from a parent gene pool Recall that from one generation to the next genotype and phenotype (gene pool) vary greatly. In nature, gene pools tend to remain stable more than in the finite example we have looked at.
  35. 35. Genetic Equilibrium Hardy-Weinberg Genetic Equilibrium  Allele frequencies in a population tend to remain the same from generation to generation unless acted on by outside influences  Based on an “ideal” population (hypothetical)
  36. 36. Hardy-Weinberg Equilibrium1. No net mutations occur (no change due to mutation)2. Individuals do not enter or leave population3. Large population (infinitely)4. Random mating required5. Selection does not occur More than anything, allows us to consider forces which may disrupt equilibrium and as a result, drive evolution
  37. 37. Disruption of Genetic Equilibrium Mutations  Caused by outside factors Migration  No immigration or emigration from population Genetic Drift  Random chance affects allele frequency (more likely in small populations) Nonrandom Mating  Humans violate with assortative mating  Animals violate by mating by geographic proximity
  38. 38. Disruption of Genetic Equilibrium Natural Selection  Stabilizing selection – individuals with average form of trait have highest overall fitness for environment  Directional selection – individuals with an extreme form of a trait have better fitness for environment  Disruptive selection – individuals with either extreme of a trait have better fitness than individuals with average form  Sexual selection – mating based on certain traits , only genes of reproducers are important in evolution
  39. 39. Speciation The process of species formation  Species – single type of organism capable of producing fertile offspring in nature Occurs with a disruption in genetic equilibrium, often a form of isolation Geographic isolation  Physical separation Reproductive isolation  Prezygotic isolation  Postzygotic isolation

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