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Evolutionary Patterns: Darwin's Observations and Natural Selection

Explore Darwin's observations on species, adaptations, and evolution in Chapter 5. Learn about natural selection, factors affecting it, role of genes, and speciation. Discover how geographical barriers and continental drift influence evolution.

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Evolutionary Patterns: Darwin's Observations and Natural Selection

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  1. Chapter 5-1 Notes Darwin’s Theory

  2. Darwin’s Observation • Species – a group of similar organisms that can mate with each other and produce fertile offspring. • Horse and donkey • Mule

  3. Galapagos Cormorant Iguanas Mainland Cormorant Iguanas Similarities and Differences

  4. Adaptations • Adaptations – a trait that helps an organism survive and reproduce

  5. Evolution • Evolution – the gradual change in a species over time • Scientific Theory – a well tested concept that explains a wide range of observation • Darwin use selective breeding to produce organisms with desirable traits • Pigeons – only many feather tailed pigeons to mate

  6. Selective breeding must happen in nature. • Darwin’s Theory – the species gradually changed over many generations and became better adapted to the new condition

  7. Natural Selection Natural Selection – the process by which individuals that are better adapted to their environments are more likely to survive and reproduce than other of the same species

  8. Factors Affecting Natural Selection • Overproduction – many offspring produce not enough resources (food, h2o , space) • Competition – food and other resources are limited must compete to survive • Variations – same species differ in traits • Selection – individual survives and reproduces.

  9. Natural Selection – can lead to evolution. • Variation gradually accumulate in a species, while unfavorable ones disappear.

  10. The Role of Genes in Evolution • Mutations – in genes cause variation • Only traits controlled or inherited by genes can be passed on to offspring.

  11. Evolution in Action • Drought on the Galapagos affected the population of finches. • Peppered moths in England

  12. How Do New Species Form? • When a group of individuals remains separated from the rest of its species long enough to evolve different traits. • Kaibab squirrel and Abert squirrel

  13. More Allopatric Speciation • Geographical barriers: mountains, oceans, rivers. A few members of a species manage to cross by a rare chance event. • This is the mechanism by which Darwin’s finches evolved into separate species in the Galapagos islands. Only very rarely can birds cross the ocean to get to other islands. • Or, the barrier develops slowly as conditions change: the gradual formation of the Grand Canyon split a population into 2 isolated groups, that have diverged into separate species, the Kaibab and Albert squirrels.

  14. Continental Drift • Species become isolated when the continent began drifting. • Ex. Australia – most mammals are marsupials. Very few marsupials in other continents.

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