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Evolutionary Theories: Lamarck vs. Darwin

Dive into the debate between Lamarck's theory of acquired characteristics and Darwin's theory of natural selection. Explore the key concepts of species, population, and the mechanisms of evolutionary change they proposed. Discover the impact of their ideas on understanding how organisms adapt and evolve.

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Evolutionary Theories: Lamarck vs. Darwin

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  1. Lamarck vs. Darwin Introduction to change in organisms

  2. What is a theory? • The most probable explanation for a large set of data based on the best available evidence • Summarizes a hypothesis or group of hypotheses that have been supported with repeated testing

  3. What is a species?What is a population? • Species – group of a single type of organisms that interbreed and are reproductively isolated • White-tailed deer • Population – refers to a group of organisms of a particular species living in a certain area. • White-tailed deer on Mt. Nebo

  4. Lamarck’s Theory • Jean Baptiste Lamarck: 1800’s • Believed: • Change Occurs Over Time • inheritance of acquired characteristics • acquired changes were passed to offspring • Law of Use and Disuse • If a body part were used, it got stronger • If body part NOT used, it deteriorated • Examples: Body builders or pierced ears

  5. Lamarck’s Theory of Evolution • Giraffes all had SHORT necks originally • Giraffe’s Necks got LONGER from stretching for food • “Acquired” trait (long necks) then passed to offspring • Giraffe population became long-necked

  6. Lamarck’s Theory of Evolution • More examples • Traits Acquired During Ones Lifetime Would Be Passed To Offspring Clipped ears and tails of dogs could be passed to offspring!

  7. Lamarck’s Mistakes • Was he correct?? • NO! • Traits are passed down from one generation to the next by GENES, not by an individual’s life experiences or activities • Lamarck did NOT know how traits were inherited (Traits are passed through genes) • Genes Are NOT Changed By Activities In Life • Change Through Mutation Occurs Before An Organism Is Born

  8. Voyage of the Beagle Charles Darwin • Born Feb. 12, 1809 • Joined Crew of HMS Beagle, 1831 • Naturalist • 5 Year Voyage around world • Astounded By Variety of Life

  9. Voyage of the Beagle During His Travels, Darwin Made Numerous Observations And Collected Evidence That Led Him To Propose A Revolutionary Hypothesis About The Way Life Changes Over Time

  10. Darwin’s Belief’s • Survival of the fittestORnatural selection • Food and resources are limited • So organisms have to COMPETE to get them (lions fight for food, space, mates …) • OVER PRODUCE too many organisms • Not all offspring will survive only the MOST FIT (not always the strongest!)

  11. What happened to the giraffe’s? • Survival of the fittest or natural selection • Natural selection said the giraffes with short necks had less food to eat • Why? • the food resources changed to leaves only on the upper branches • What happened? • short necks could not reach upper branches and did not survive (couldn’t pass on genes) • Long neck giraffes survived & reproduced because they were able to reach the food

  12. Evolution is the slow, gradual change in a population of organisms over time… a looooooooong time!

  13. Where do we see this change? • When there is an unequal ability of individuals to survive and reproduce … • This leads to a gradual change in a population with favorable characteristicsaccumulating over generations • Most fit “naturally” selected • New species evolves

  14. Natural Selection • How does Selection occur? • Selection of the most fit can occur from several factors: • Variations exist among individuals in a population • Competition for limited resources • Overpopulation • Predation/Disease

  15. Example of Natural Selection • A classic example of natural selection is the Peppered moths during Industrial Revolution in Europe

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