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Unraveling Darwin's Theory: Natural Selection Explained

Dive into Charles Darwin's groundbreaking theory of natural selection and evolution, exploring how living things change over time, the role of adaptations, and the misconceptions surrounding this fundamental idea in biology.

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Unraveling Darwin's Theory: Natural Selection Explained

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  1. Natural Selection Darwin’s Big Idea

  2. Charles Darwin (born February 12, 1809) was a British scientist. He sailed around the world as a naturalist, recording what he saw. He made important observations and connections that no scientist had figured out before. You will read more about his discoveries tomorrow.

  3. Natural Selection • The Theory of Natural Selection is so simple that anyone can misunderstand it…. (Anonymous) • Charles Darwin (1809-1882) saw three problems in need of a solution. • Darwin was not the only one to notice these problems. • Other scientists, including Alfred Russel Wallace, shared ideas with Darwin and contributed to figuring out the solution.

  4. Problem #1 • Living things on Earth change over time. • The fossil record shows that in the past there were a lot of plants and animals that are now extinct.

  5. Problem #2 • Living things could be classified into different categories. • People were big into classifying stuff. • It was pretty obvious that there was a relationship between different species. • Different birds, different grasses, different cats etc

  6. Problem #3 • Living things have adaptations. • Different kinds of teeth for different animals, say carnivore ripping teeth and herbivore grinding teeth • Different tissues within species • Heart vs. eye etc.

  7. The Solution! • Darwin figured out a theory that made sense of all of these problems. • He called it Natural Selection.

  8. Darwin’s Logic • Fact 1: Species reproduce exponentially. • Fact 2: Populations stay constant. • Fact 3: Resources are limited. • Inference 1: There must be competition to survive.

  9. Darwin’s Logic • Fact 4: Individuals in a population vary. • Fact 5: Variations are inherited genetically. • Inference 2: Some individuals have traits that help them survive better than others (natural selection). • Inference 3: Over time adaptations accumulate in a populations, creating different species (evolution).

  10. How does it work? • Selection determines which individuals grow up and have babies. • This selection is done by the environment. • The individuals who are best fit to their environment survive and reproduce. • They pass these fit traits on to their offspring.

  11. The Solution • “Descent with modification from a common ancestor, NOT random modification, but, modification shaped by natural selection.” • Darwin

  12. Misconceptions • Lamarckism • Traits that you develop during your lifetime can be passed on. • Giraffes really wanted leaves, so they stretched their necks and….. • Correction: Individuals cannot evolve.

  13. Misconceptions • There is a plan or goal to evolution. Organisms can change because the want to. • Correction: Traits change because of genetics mutations that happen by chance.

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