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Evolutionary Theories: Darwin and Lamarck

Explore the evolution theories of Charles Darwin and Jean-Baptiste Lamarck, delving into their observations, contributions, and impact on the scientific world. Understand concepts like natural selection, inherited variation, and evidence of evolution.

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Evolutionary Theories: Darwin and Lamarck

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  1. Theory of Evolution Chapter 15: pgs 368 – 391

  2. What is Evolution? • Evolution • Change over time • Process by which modern organisms have descended from ancient organisms • Considered a theory • Is a well-supported testable explanation of phenomena that have occurred in the natural world

  3. Charles Darwin • Contributed the most to our current understanding of evolution • Joined the crew of the H.M.S. Beagle • Sailed around the world • Darwin's major focus was the Galapagos Islands

  4. Darwin’s Observations • Noticed that there were NUMEROUS variations of similar species • Why do some species inhabit some countries, but not others? For Example: Rabbits & Kangaroos • Fossils needed to be considered • Preserved remains of ancient organisms

  5. Galapagos Islands • One of the many spots the H.M.S. Beagle visited • Darwin’s Favorite & Most Influential • Small group of islands off of South America • Islands close in location, but different climates! • Vegetation sparse on some & others abundant • Animals of interest • Tortoise’s: Originally did not notice shell difference • Birds: beaks were shaped differently (journey home) • Especially island to island

  6. Jean-Baptiste Lamarck • Published hypotheses in 1809 (Year Darwin was born!) • Proposed: that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime. These traits could then be passed on to their offspring. Over time, process led to change in species

  7. Darwin Presents His Case • Continuously studied specimens from the islands • Determined that birds were actually related & NOT found anywhere else on Earth • Published “The Origin of Species” (Book) • Challenged fundamental scientific beliefs & religion • At first, most people did not support his findings • Others considered him to be brilliant • Proposed a mechanism called “Natural Selection”

  8. Inherited Variation & Artificial Selection • Inherited Variation • Exists in Nature & on Farms • Some plants (same species) produce larger fruit • Some animals (Cows) produce more milk than others • Caused by variation in genes • Heredity was unknown during Darwin’s era • Artificial Selection • Nature causes/allows the variation • Humans then select favorable traits

  9. Natural Selection • All species struggle for existence • Example: Competition for food, shelter, mates, etc. • Certain traits allow similar species to survive • Survival of the Fittest • How well suited an organism is to its environment • Fitness- the ability of an individual to survive and reproduce in its specific environment • Adaptation - Any inherited characteristic that increases an organisms chance of survival • Examples: Porcupine’s Quills or Cheetah’s speed

  10. Evidence of Evolution • Fossil Record • Helped Darwin to argue how animals could change over time • Geographic Distribution of Living Species • Homologous Body Structures • Body structure, like a fin, leg, or wing • Allows researchers to compare similarities and differences • Vestigial organ • Structure that remains, but no longer has a function; like legs on a snake • Similarities in Embryology • Appearance of developing embryos

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