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Natural selection notes
Natural selection notes
Natural selection notes
Natural selection notes
Natural selection notes
Natural selection notes
Natural selection notes
Natural selection notes
Natural selection notes
Natural selection notes
Natural selection notes
Natural selection notes
Natural selection notes
Natural selection notes
Natural selection notes
Natural selection notes
Natural selection notes
Natural selection notes
Natural selection notes
Natural selection notes
Natural selection notes
Natural selection notes
Natural selection notes
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Natural selection notes


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  • 1. Natural Selection Notes
    • Learning Targets:
    • 2. Students will be able to defend the evidence for evolution through natural selection in terms of the fossil record, homologous structures, artificial selection, and competition.
    • 3. Students will use the principles of natural selection to explain the differential survival of groups of organisms as a consequence of: the potential for a species to increase its numbers; the genetic variability of offspring due to mutation and recombination of genes; a finite supply of the resources required for life; and, the ensuing selection based on environmental factors of those offspring better able to survive and produce reproductively successful offspring.
  • What is a Theory?
    • Theory- a well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses
    • 4. Law- a descriptive generalization about how some aspect of the natural world behaves under stated circumstances and that carries the weight of scientific evidence
    • 5. Fact-an observation that has been repeatedly confirmed
    • 6. Hypothesis- a testable statement about the natural world
    • 7. Belief- a psychological state in which a person holds a premise (or statement) to be true.
  • Evolution- Change over time
    Evolution by natural selection is a theory
    Why do we study how organisms change over time?
  • 8. Extinction Game: Using models in Science
    Why did we use this game? Why not do a lab?
    Bunnies could represent any species/organism
    Variation occurred through mutation and genetic shuffling (recombination)
    The environment had an effect on the advantages of fur color
  • 9. Extinction Game: Using models in Science
    There was competition for food or predator evasion
    The population changed over time after many generations depending on the specific selection factors
  • 10. The Earth is very old
    Earth is about 4.5 billion years old
    Many geologists confirmed this approximate date through determining the age of rock formations and the time it would take for them to form
  • 11. The Earth is very old
    If weathering and other geological processes have been happening at the same rate for a very long time (or always) then the Earth must be several billion years old to account for the formations.
    Chemical analysis of ice cores and radio active fluorine and carbon have also been helpful in explaining the age of rock.
  • 12. Why does it matter how old the Earth is?
    What can we infer if the Earth were only a few thousand years old?
  • 13. Charles Darwin
    Darwin published On the Origin of Species in 1859.
    In the book, Darwin supplied evidence that evolution has occurred AND explained his ideas about how evolution occurs.
  • 14. Darwin continued…
    Darwin’s theory was based on artificial selection. In artificial selection, nature provided the variation, and humans selected those variations that they found useful. For example, animal breeders used only the largest hogs, fastest horses, or cows that produced the most milk for breeding.
  • 15. How we see genetic change
  • 16. Natural Selection
    Darwin thought that a similar process occurs in nature. He called this natural selection. This process can be summed up as follows:
    Individuals differ, and some of the differences can be passed on to their offspring
    More offspring are produced than can survive and reproduce.
  • 17. Natural Selection
    3. There is competition for limited resources, or a struggle for existence
    4. Individuals best suited to their environment survive and reproduce most successfully. In other words, there is survival of the fittest. Fitness is the ability to survive and reproduce in a given environment. It results from adaptations.
    5. Adaptations are inherited traits that increase an organism’s chance of survival. Only the fittest organisms pass on their traits. Because of this, a species changes over time
  • 18. Common Descent
  • 19. Common Descent
    Darwin argued that species alive today descended with modification from species of the past. This is called the principle of common descent.
    There is evidence for a single tree of life, He presented four types of evidence in support of evolution.
  • 20. What are the five (5) parts of the process of Natural Selection?
  • 21. Common Descent
    Darwin had four pieces of evidence for this idea:
    Homologous Structures
    Fossil record
    Geographic distribution of similar species
    Similarities in early stage of development
  • 22. The fossil record- some organisms went through drastic change while others went extinct or stayed relatively the same over time.
  • 23. Geographic distribution of living species
    The presence of similar but unrelated organisms in similar environments suggests the action of natural selection
  • 24. Homologous structures
    have different mature forms but develop from the same embryonic tissues. (Some homologous structures no longer serve major roles in descendants. If the structures are greatly reduced in size, they are called vestigial organs.
  • 25. Similarities in early development
    The early stages, or embryos, of many animals are very similar.
  • 26. Our inferences…
  • 27. What does this mean for humans?
    This does not mean scientists believe humans come from monkeys but it does mean that long ago there may have been a common ancestor of both chimpanzees and humans!