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Theories of Evolution. Darwin vs. Lamarck. Lamarck. Darwin. Jean-Baptiste LaMarck. French, Early 1800’s Theory of Inheritance of Acquired Characteristics Two main points…. 1. Principle of Use & Disuse: Most used body structures develop, unused structures waste away.

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darwin vs lamarck

Theories of Evolution

Darwin vs. Lamarck




jean baptiste lamarck
Jean-Baptiste LaMarck
  • French, Early 1800’s

Theory of

Inheritance of

Acquired Characteristics

  • Two main points…
1. Principle of Use & Disuse:
  • Most used body structures develop, unused structures waste away

2. Inheritance of Acquired Characteristics:

  • Once the structure is modified, the new trait can be inherited (passed to offspring)
why we don t believe him
Why we don’t believe him…
  • Genetics:Gregor Mendel discovered that traits are passed down through GENES (which aren’t affected by the outside world in that way)
  • Experiments: show that changes that occur in an animal’s life are not passed on to its offspring
charles darwin the father of evolution
Charles Darwin“The Father of Evolution”
  • 1831- sailed on the HMS Beagle to the Galapagos Islands.
  • Studied many species of finches.
  • Published book in 1845:
    • “On the Origin of Species by Natural Selection”
darwin s theory of evolution don t copy all this it s on your handout
Darwin’s Theory of Evolution(don’t copy all this it’s on your handout) 

“Natural Selection”

“Survival of the Fittest”

natural selection
Natural Selection
  • Process by which favorable heritable traits become more common in successive generations of a population of reproducing organisms, and unfavorable heritable traits become less common.
four main points
Four main points…
  • 1. More organisms are produced than can survive…leads to COMPETITION OVER RESOURCES
      • Ex’s of resources…
        • Water
        • Food
        • Habitat
        • Mates
3 some variations are favorable increase chances for survival reproduction
3. Some variations are FAVORABLE (increase chances for survival/ reproduction)
  • Male vs. Female Cardinals
  • Male color attracts female= reproductive advantage
better adapted individuals survive and reproduce
Better adapted individuals survive and reproduce
  • These are the individuals that will pass on their genes to the next generation.
  • This can change the GENE POOL:
    • Includes all the genes of every reproductive member of a population
what the theory of evolution is not
What The theory of evolution IS NOT!!!
  • It does NOT occur in INDIVIDUALS…only populations!
  • It does NOT happen quickly…the Earth has a Looooooong history!
  • It does NOT explain how life came to be on Earth, just how it evolved after it was here.
  • It does NOT have any driving force except the competition for limited resources.
darwin s finches p 558
Darwin’s Finches…p 558
  • Illustrate SPECIATION: when a species breaks into two (or more)
    • The organisms in the two species can no longer…
  • What could cause this to happen?
    • Geographic barriers
    • Occupy a new niche/habitat
    • Reproductive Isolation-
types of natural selection
Types of Natural Selection
  • Stabilizing Selection
    • Occurs when natural selection works against the 2 extremes of a trait to make the population more uniform.
stabilizing selection21
Stabilizing Selection
  • Birth weight of babies
    • Babies that are too big or too small might have less chance of being born healthy.
natural selection22
Natural Selection
  • Directional Selection
    • Selects the extreme of 1 trait.
directional selection
Directional Selection
  • In a population of plants, flowers with the brightest color might be selected for in order to attract the most pollinators.
natural selection24
Natural Selection
  • Disruptive Selection
    • Selects against the mean of the population.
disruptive selection
Disruptive Selection
  • If there are 2 types of seeds to eat for a population of birds, either of 2 different beak shapes (sharp or blunt) might be selected for, but a beak that’s the average of the 2 shapes might not be particularly good at eating either seed, so it would be selected against.
evolution types
Evolution Types
  • Convergent Evolution
    • Acquiring the same biological trait in unrelated lineages
    • These traits may be a result of occupying similar environments.
evolution types29
Evolution Types
  • Divergent Evolution
    • The accumulation of differences between groups which can lead to the formation of new species, usually a result of different groups of the same species adapting to different environments, leading to natural selection defining the success of specific mutations.
evolution change over time
Evolution- “Change Over Time”

All of the changes that have occurred in living things since the beginning of life on Earth

700 million years ago
700 million years ago…


three important points
Three important points…
  • Evolution occurs over MANY generations
  • Evolution occurs within POPULATIONS (NOT individuals)
  • Evolution involves genetic changes in a SPECIES
    • (Members of a species interbreed to produce healthy, fertile offspring)