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Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
Evolution notes #1
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Evolution notes #1

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  • 1. Development ofEvolutionaryThought
  • 2. Isn’t evolution “just” atheory?•Scientific theories are explanationsthat are based on lines of evidence,enable valid predictions, and havebeen tested in many ways.
  • 3. Evolve – change overtime
  • 4. What is Evolution? Evolution- a change in the genetic composition of a population over time.
  • 5. Paleontology & Evolution Older layers of sedimentary rock (the layers on the bottom) contain fossil species very dissimilar from modern life. Each layer (stratum) is characterized by a unique group of fossil species. As you move upward through the layers, you find species more and more similar to modern life.
  • 6. James Hutton - 1795 A Scottish geologist proposed that it was possible to explain the various landforms by looking at mechanisms currently operating in the world Proposed that the earth was much more than a few thousand years old
  • 7. Jean Baptiste Lamarck Theory of evolution in 1809 mechanism: – use and disuse - the idea that the parts used the most grow stronger; the parts that don’t get used deteriorate – inheritance of acquired characteristics - the modifications that an organism acquires during its lifetime can be passed along to its offspring recognized adaptation to environment as a primary product of evolution
  • 8. Charles Darwin (1809-1882) Father of modernevolutionary theory Born in England HMS Beagle Galapagos Islands
  • 9. What is an adaptation? An inherited characteristic that increases an organism’s ability to survive and reproduce in its specific environment.
  • 10. Darwin’s Observations Darwin noticed that every bird on the Galapagos Islands was a modified finch. The only differences in the birds were their beaks and what they ate. These finches looked very similar to one type on South American continent, but none of these were found in S.A.“How did one species change into a different species?”
  • 11. The Galapagos Finches
  • 12. He wrote On The Origin ofSpecies (1859) after 20years of study.
  • 13. Darwin’s Four Postulates Individuals within a population vary in their traits. Some of these traits are heritable. More offspring are produced than can survive because of limited resources. Individuals with advantageous traits will survive and reproduce.
  • 14. What is natural selection?  Natural selection - a population of organisms can change over generations if individuals having certain heritable traits leave more offspring than others  Natural selection is the mechanism by which evolution is proposed to occur
  • 15. What is “artificialselection”? Nature provides the variation among different organisms, and humans select variations that they find useful. Example: breeding cows, horses, hogs Darwin used this to help support his case for natural selection.
  • 16. Descent withmodification the history of life is like a tree, with multiple branching and re-branching from a common trunk all the way to the tips of the youngest twigs most branches of evolution are dead ends; about 99% of all species that have ever lived are extinct
  • 17. Figure 22.7 Descent with modification
  • 18. Survival of the Fittest• Another name for Darwin’s theory of natural selection. •Biologists use the word fitness to describe how good a particular genotype is at leaving offspring in the next generation relative to how good other genotypes are at it.
  • 19. Mechanisms ofEvolution
  • 20. Natural Selection &Survival of the Fittest(already discussed with Darwin)
  • 21. Modern Ideas Darwin + Mendel’s work and the work of others, have lead to modern ideas about evolution.Another mechanism of evolution is Genetic Drift (random changes in genes) which occurs through natural selection.
  • 22. Modern Ideas Speciation – formation of new species is due to gradual genetic changes, and that large scale evolution is the result of a lot of small scale evolution. Microevolution – process responsible for the variations that exist within a species, or a change in the allele frequency.
  • 23. Modern Ideas Macroevolution – evolution that occurs between species. Examples: the separation of a species to form two distinct species or the development of a new species from many small changes within an existing species
  • 24. Gene Flow The change in occurrence of genes in a population. This occurs when an individual leaves a population (emigration) or new individual joins a population (immigration).
  • 25. Genetic Drift Random changes in the occurrence of genes through chance events. Can occur when a few individuals of a population break off from the original group and start their own population (founder effect). Large number of population is killed due to disease, starvation, natural disaster, etc. (bottle necking)
  • 26. Punctuated Equilibrium Darwin felt that biological change was slow and steady as indicated in the fossil record. Modern scientists see that this pattern does not always hold. (Darwin’s finches) The term punctuated equilibrium is used to describe a pattern of long, stable periods interrupted by brief periods of more rapid change. This is still controversial today.
  • 27. Evidence ofEvolution
  • 28. Fossil Evidence Fossils provided a detailed record of evolution. Fossils formed in different layers of rock were evidence of gradual change over time.
  • 29. Homologous BodyStructures Structures in different species that may perform different functions but are similar because of their common ancestry Vestigial organs - structures of no apparent function to an organism; leftover from ancestry; ex - snakes have leg & pelvis bones
  • 30. Figure 22.14 Homologous structures: anatomical signs of descent withmodification
  • 31. More homology… Molecular homology - similarity in DNA sequence between an ancestor and its progeny Embryological homology - similarities only apparent in embryological development – ex: all vertebrate embryos have “pharyngeal pouches” which later become gills or Eustachian tubes
  • 32. Patterns ofEvolution
  • 33. Adaptive Radiation When a single species or a small group of species has evolved into several different forms that live in different ways. Example: Darwin’s finches (more than a dozen evolved from a single species)
  • 34. ConvergentEvolution Explains how unrelated species can develop similar characteristics Porpoise (mammal) & Shark (fish) Unrelated animals, but share similar characteristics to suit their environment
  • 35. Analogous structures Show similarity in structure based on adaptation for the same function, not common descent.
  • 36. Divergent Evolution Suggests that many species develop from a common ancestor Penguins (wings for swimming) & vultures (wings for flying) Both are birds, diverged from a common ancestor
  • 37. Co-evolution When two or more organisms in an ecosystem evolve in response to each other. Example: Flowers and their pollinators
  • 38. Camouflage – an animallooks like its environment. http://rainforests.mongabay.com/0306.htm
  • 39. Mimicry- when animals havecoloring and markings tolook like another animal
  • 40. Warm Up!1. What is the difference between “evidence” of evolution and “mechanisms” of evolution?2. What is biological fitness?3. Explain in your own words the term “natural selection”

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