February 26

I wanted to get a review sheet posted as soon as possible for students to explore – here’s an outline!



  1. Darwin

    1. Traveled to Galapagos Islands on the HMS Beagle
    2. Observed the different beaks of finches, and different food sources
    3. Concluded evolution happens by means of natural selection
  2. Natural Selection

    1. Organisms reproduce more offspring than can survive
    2. There is genetic variation within a population
    3. Selection happens (some better equipped, some not)
    4. Favorable traits accumulate (dominant genes)
  3. Adaptation

    1. An adaptation is an inherited trait that helps an organism survive
    2. It’s genetic – it does not happen because an organism tries harder.
  4. Evidence for Evolution

    1. Fossil Record
      1. Fossils tell how old something is (sedimentary layers/carbon dating)
      2. Fossils tell us what came first (from dating, we can create a timeline)
    2. DNA Evidence
      1. Our DNA codes for traits that are similar in different kinds of animals
      2. Species that share more similarities in their DNA base sequences aremore closely related
      3. Scientists hypothesize that if two species have similarities in theirbase sequences, they share a common ancestor
    3. Comparative Anatomy
      1. Homologous structures suggest a common ancestor
      2. Analogous structures show that very useful adaptations can evolve more than once, and in different ways
  5. Cladogram

    1. A cladogram shows the evolutionary relationships between groups ofliving things. It is like a family tree for species
    2. The closer two species are on the cladogram, the more closely they arerelated. This means they evolved apart more recently
    3. Organisms with more of the traits evolved later, so they go on the right
  6. Extinction – When a species not longer exists, due to:

    1. Increased Competition -­‐ organisms share food, water, and shelter and when it starts to run out, they compete with each other
    2. New Predators -­‐ new species can enter an area and prey on animals that do not have adaptations to protect themselves
    3. Loss of Habitat -­‐ habitats can get destroyed by pollution, natural disasters such as floods, storms, fires
    4. Catastrophic Event -­‐ asteroids can destroy life on the planet
  7. Speciation – The formation of a new species. Three stages:

    1. Isolation -­‐ happens when a population becomes divided by an event (such as floods, volcanic eruptions, mountain formation, earthquakes, and storms)
    2. Adaptation -­‐ as the environment changes, the population that lives there undergoes natural selection, and each separated population becomes adapted to their environment
    3. Differentiation -­‐ happens when the isolated populations become so different that they can no longer interbreed, even if they could unite again.