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Chapter 16: Darwin’s Theory of Evolution

Chapter 16: Darwin’s Theory of Evolution. Darwin’s Voyage of Discovery. Darwin’s Journey. Charles Darwin British scientist and naturalist 5 year journey around the world on the HMS Beagle Hit Australia, Africa, and South America Collected plants and animals

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Chapter 16: Darwin’s Theory of Evolution

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  1. Chapter 16: Darwin’s Theory of Evolution Darwin’s Voyage of Discovery

  2. Darwin’s Journey • Charles Darwin • British scientist and naturalist • 5 year journey around the world on the HMS Beagle • Hit Australia, Africa, and South America • Collected plants and animals • This journey was the foundation for his theory of evolution

  3. Observations aboard the Beagle • 1. Species vary globally • Ex: Emus, Rheas, and Ostriches • Flightless birds found on 3 continents • Similar habitats but different animals • 2. Species vary locally • Ex: Tortoises of the Galapagos Islands • Different animals in the same environment • 3. Species vary over time • Ex: Fossils of organisms • Some looked similar to animals today; others didn’t

  4. Chapter 16: Darwin’s Theory of Evolution Ideas that shaped Darwin’s Thinking

  5. Role of Geology • People believed Earth was not old and not changing • Geology was emerging and showing something else • James Hutton (1726-1797) • Geological processes shape the land • Forces push mountains up • Deep time: Earth’s history so long we can’t imagine it • Charles Lyell (1797-1875) • Principles of Geology • Laws of nature don’t change over time • Changes in landscape take millions of years

  6. Lamarck’s Evolutionary Hypothesis • Jean Baptiste Lamarck (1744-1829) • Created the first theory of evolution • All organisms born with desire to become better • Organisms could change bodies to adapt to environment • Acquired characteristics: Traits that change during organism’s life • Acquired traits can be passed onto offspring • Although most ideas were wrong, he was on the right track • Made the connection between an organism’s body and its environment

  7. Role of Economics • Thomas Malthus (1766-1834) • English economist • Ideas designed for human population but can be used for all organisms • People born quicker than people dying • This leads to overcrowding • Overcrowding lead to conditions that slow growth • Important that only a few survive but which ones

  8. Artificial Selection • People chose best traits within organisms and breed them • Object is to create bigger and better products • Variation can occur in the wild as well as domestic • Ex:

  9. Chapter 16: Darwin’s Theory of Evolution Darwin Presents his Case

  10. Evolution by Natural Selection • 1. Struggle for Existence • Members of population compete for food, water, and living space • Those that don’t get enough won’t survive • 2. Variation and Adaptation • Variation • Heritable traits: traits passed onto offspring • Heritable traits make survival easier • Adaptation • Any heritable trait that allows an organism to survive in the environment

  11. Evolution by Natural Selection • 3. Survival of the Fittest • Differences in adaptations affect fitness • Fitness: How well an organism and survive and reproduce in its environment • Individuals with these adaptations will survive more than those without the adaptations

  12. Evolution by Natural Selection • 4. Natural Selection • Organisms with the best traits to match their environment will survive • 3 conditions needed for it to exist • 1. More individuals being born than dying • 2. Heritable traits in the population (variation) • 3. Some individuals have traits that all them a better chance to survive • If environment changes, the population will change

  13. Common Descent • Every organism today descended from parents who survived and reproduced • Descent with modification • Older species evolve into new species • Deep time allows Darwin to validate natural selection • Fossil Record is evidence of descent with modification • Common Descent • All organisms share an ancient common ancestor

  14. Chapter 16: Darwin’s Theory of Evolution Evidence of Evolution

  15. Evidence of Evolution • Biogeography • Study of where organisms live and where ancestors lived • 2 patterns arose: • 1. Closely related organisms that lived in different environments showed many differences • Each environment is different and forces organisms to adapt differently • 2. Distantly related organisms that live in similar environments are often similar • Organisms will have similar adaptions if they are in similar environments

  16. Evidence of Evolution • Body Structures • Homologous Structures • Similar structures found in different organismsallow us to say they have been inherited from a common ancestor

  17. Evidence of Evolution Analogous Structures • Show us that organisms that have structures with similar functions but different structures are not as closely related as thought to be • Ex: different wings in flying animals

  18. Evidence of Evolution Vestigial Structures • Structure in an organism that was once useful to a previous ancestor but no longer has a function in organism • Ex: Hip bone in whales and dolphins

  19. Evidence to Evolution • Embryology • At an embryonic stage, all organisms look and develop in the same way

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