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The Theory of Evolution

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Chapter 13 Lecture

Chapter 13 Lecture

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  • 1. The Theory ofEvolution Chapter 13 – Sect. 1: Natural Selection
  • 2. Charles Darwin - 1859  Published convincing evidence that species evolve  Proposed a reasonable mechanism to explain how evolution occurs
  • 3. Darwin’s Voyage on theHMS Beagle
  • 4. Darwin’s Voyage on theHMS Beagle  1831-1836 (5 year voyage)  Darwin was 22 years old at the start  Naturalist – someone who studies nature  Ships purpose was to survey the coast of South America
  • 5. Darwin’s FinchesDarwin observed that many of the plants and animals of the Galapagos Islands resembled but were not the same as those on the nearby coast of South America Population – all the individuals of a species that live in a specific geographical area and that can interbreed
  • 6. Natural Selection  Individuals that have physical or behavioral traits that better suit their environment are more likely to survive and will reproduce more successfully than those that do not have such traits  These advantageous traits are adaptations  As a result, the nature of the population will gradually change – evolution!
  • 7. Harsh Criticism  Darwin wrote down his ideas about evolution and natural selection in 1844  He did not try to publish his work until 1858  The theory of evolution goes against religious beliefs and was not accepted by the public in general
  • 8. On the Origin of Speciespublished in 1859 (pg. 280 1-4) Inherited variation exists within the genes of every population or species (the result of random mutation or translation errors) In a particular environment, some individuals of a population or species are better suited to survive and have more offspring Over time, the traits that make certain individuals of a population able to survive and reproduce tend to spread in that population There is overwhelming evidence from fossils and many other sources that living species evolved from organisms that are extinct
  • 9. Reproductive Isolation  Two populations of the same species do not breed with one another because of geographic separation, a difference in mating periods, or other barrier to reproduction  These isolated populations will become more different over time until they are no longer able to breed with one another
  • 10. The Tempo of Evolution
  • 11. The Theory ofEvolutionChapter 13 – Sect. 2: Evidence of Evolution
  • 12. Most Scientists Agree on the Following: Earth is about 4.5 billion years old. Organisms inhabited Earth for most of its history. All organisms living today share common ancestry with earlier, simpler life forms.
  • 13. The Fossil Record  The preserved or mineralized remains or imprint of an organism that lived long ago.  Provide a record of Earth’s past life forms  Evidence of evolution can be seen in the fossil record.
  • 14. Formation of Fossils  The fossil record is not complete.  Fossils do not form in all environments  Most fossils form when organisms are rapidly buried in fine sediments  Bodies may decay too quickly or be eaten or scattered  Fossils are most likely to form in:  Wet lowlands, slow-moving streams, lakes, shallow seas, and areas near active volcanoes
  • 15. Anatomy & Development  Comparisons of the anatomy of different types of organisms reveal basic similarities in body structures  The structures may have different functions in different organisms  Ex.) bones may be present in both organisms but are reduced in size and have no use or less important function
  • 16. Vestigial Structures Reduced in size or function, but may have been complete in an ancestor  Ex.) hind limbs of whales
  • 17. Homologous Structures  Structures that share a common ancestry  ex.) forelimbs of vertebrates
  • 18. Changes in DNA  Mutation – a change in the nucleotide- base sequence of a gene or DNA molecule  If species have changed over time, then the genes that determine the species’ characteristics should also have changed by mutation
  • 19. The Theory ofEvolutionChapter 13 – Sect. 3: Examples of Evolution
  • 20. Natural Selection at Work  Environment dictates the direction and amount of change in evolution  If the environment changes in the future, the set of characteristics that most help an individual reproduce successfully may change
  • 21. Factors in Natural Selection(pg. 288 1-4)  All populations have genetic variations.  The environment presents challenges to successful reproduction.  Individuals tend to produce more offspring than the environment can support.  Individuals that are better able to cope with the challenges presented by their environment tend to leave more offspring.
  • 22. Examples of Natural Selection  Strains of lung disease tuberculosis (TB) becoming resistant to certain antibiotics  DNA in each strain is different = evolution & natural selection  Darwin’s finches developed different size and shape beaks based on food sources  Finches with proper beak for food survive = evolution & natural selection
  • 23. Formation of New Species  Divergence – accumulation of differences between groups  Leads to the formation of new species  Subspecies – populations of the same species that differ genetically because of adaptations to different living conditions  Can become so different that can no longer interbreed successfully  Speciation – the process by which new species form