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Chapter 15 – Darwin’s Theory of Evolution

Chapter 15 – Darwin’s Theory of Evolution. Charles Darwin. Made observations and collected evidence that led him to propose a theory on evolution Theory – a well supported testable explanation Evolution – genetic changes in a population over time. Darwin’s 5 year voyage on the Beagle….

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Chapter 15 – Darwin’s Theory of Evolution

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  1. Chapter 15 – Darwin’s Theory of Evolution

  2. Charles Darwin • Made observations and collected evidence that led him to propose a theory on evolution • Theory – a well supported testable explanation • Evolution – genetic changes in a population over time

  3. Darwin’s 5 year voyage on the Beagle…

  4. Darwin’s Observations • An enormous number of species live on Earth • Species: interbreeding groups of organisms that can produce healthy, fertile offspring. • Galapagos Islands – Saw tortoises, iguanas, and finches, all varying in predictable ways among the different islands

  5. Pinta Tower Marchena Pinta IslandIntermediate neck and shell James Fernandina Santa Cruz Isabela Santa Fe Hood Island Long neck and open shell around legs Floreana Hood Isabela Island Short neck and dome-shaped shell On the Galapagos Islands… Intermediate vegetation Sparse Vegetation Abundant Vegetation

  6. Section 15-3 Darwin Presents His Case

  7. Darwin’s Variation and Selection • Variation – members of each species vary from one another • Ex: some plants in a species bear larger fruit; some cows give more milk • Artificial selection - Pick and choose traits that we like/want • Example: • Humans select what we want in a mate – looks, personality, character…..

  8. Adaptation – an inherited trait that increases a population’s chances of survival • Adaptations help populations fit in their niche • Niche: place and role of each organism in the environment • where organisms live, what they eat, their predators, and biotic conditions

  9. Adaptation • Some adaptations involve changes in the structure of body parts: mimicry and camouflage. • Mimicry enables an organism to copy the appearance of another species.

  10. MIMICRY

  11. Viceroy – mimics the monarch to avoid being eaten Monarch – tastes bad to birds

  12. Milk Snake Coral Snake

  13. Camouflage is a structural adaptation that enables an organism to blend in with its surroundings.

  14. CAMOUFLAGE

  15. Darwin’s Conclusions: • Struggle for Existence: organisms compete for resources (winners and losers) • food, water, and space • Survival of the Fittest: (AKA Natural Selection) individuals that are better suited survive and reproduce most successfully; increases fitness(ability to survive and reproduce) • Descent with modification – All species evolved from ancestors with changes, but look similar to ancestors • implies species have a common descent

  16. Evidence of Evolution

  17. 1) Fossils • Found in different layers, which represents life forms at different times • Show when organisms became extinct and how organisms have changed over time • Certain fossils are only found in certain layers

  18. 2) Geographic Distribution • Populations of the same species adapt to different geographic environments and change over time (descent with modification)

  19. Geographic Distribution of Living Species Beaver Beaver Muskrat Beaver andMuskrat Coypu Capybara Coypu andCapybara NORTH AMERICA Muskrat SOUTH AMERICA Capybara Coypu

  20. 3) Similarities in Embryology • Vertebrates go through similar early stages of development • Embryonic cells develop in similar patterns to produce common tissues and organs of all vertebrates • Similar embryology also suggests similar genes

  21. What do you notice about these structures?

  22. 4) Homologous Body Structure • Different mature body parts develop from the same embryonic tissues • Four limbs of all vertebrates suggests they descended from common ancestors

  23. Homologous Body Structures Turtle Alligator Bird Mammal Ancient lobe-finned fish **The color coordination of the bones indicate that they came from the same embryonic tissue; therefore, they are homologous.

  24. Vestigial Organs • Structures that are useless or reduced in size of one organism but are homologous and useful to another organism • Examples: • Tailbone in humans • Femur bone in whales and snakes

  25. Vestigial Organs Femurs are used to walk—it is the largest leg bone in humans. Whales have femurs, yet they cannot walk. This is an example of a vestigial structure.

  26. AND … what do you notice about these structures?

  27. Analogous Structures • Have same function, but NOT similar structure (develop from different embryonic tissues) • Example: • Bird wing vs. Insect wing—Both are used for flying. Birds’ wings have bones, insects’ wings do not; therefore, they have developed from different tissues

  28. Analogous Structures Top: Bird’s wing Bottom: Insect’s wing Both used for flying, but they come from different embryonic tissues.

  29. 5) DNA Sequences • Similar base pair sequences in DNA can link similar organisms in evolutionary descent • Therefore, we can also determine amino acid sequences, too

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