The Historical Context for Evolutionary Theory (you may have to search around a bit in the overview, and concepts 19.1 and 19.2 to appropriately answer questions 1 and 2).
1. Explain the mechanism for evolutionary change proposed by Charles Darwin in On the Origin of Species.
Darwin proposed natural selection as the mechanism for evolutionary change. Organisms with traits that enhance survival and reproduction are more likely to pass those traits to offspring, leading to gradual adaptation over generations. |
2. Define evolution and adaptation.
Evolution the change in allele frequencies in a population over generations Adaptation inherited characteristics that enhance an organism’s ability to survive and reproduce in a specific environment. |
3. Compare and contrast Aristotle’s scala naturae to Carolus Linnaeus’ classification scheme.
Aristotles’ classification: A hierarchical structure of life, with organisms ranked from simplest to most complex, assuming species were fixed. Linnaeus’ classification: A binomial nomenclature system grouping organisms based on shared characteristics, laying the groundwork for evolutionary relationships. |
4. Describe the theories of catastrophism, gradualism, and uniformitarianism and who was associated with them.
Catastrophism (Georges Cuvier): Earth's history shaped by sudden, short-lived, violent events.
Gradualism (James Hutton): Geological changes occur slowly over long periods.
Uniformitarianism (Charles Lyell): Earth's processes are uniform over time, influencing Darwin’s idea that small changes accumulate. |
5. Explain the mechanism for evolutionary change proposed by Jean-Baptiste de Lamarck. Explain why modern biology has rejected Lamarck’s theories.
Lamarck proposed the inheritance of acquired characteristics, suggesting organisms develop traits through use or disuse and pass them to offspring. It was rejected because acquired traits do not alter DNA; genetic changes occur through mutations and selection, not use/disuse. |
The Darwinian Revolution
6. Describe how Darwin’s observations on the voyage of the HMS Beagle led him to formulate and support his theory of evolution.
Darwin observed variations in species across different islands (e.g., finch beak variations in the Galápagos). He concluded species adapt to environments over time, leading to descent with modification. |
7. Explain how the principle of gradualism and Charles Lyell’s theory of uniformitarianism influenced Darwin’s ideas about evolution.
Darwin applied these geological ideas to biology, reasoning that small changes over long periods could explain the gradual evolution of species. |
8. Explain what Darwin meant by “descent with modification.”
All species share common ancestors, and over time, small heritable changes accumulate, leading to diversity. |
9. Explain what evidence convinced Darwin that species change over time.
Fossils, biogeographical distribution of species, homologous structures, and direct observations of adaptation (e.g., finches and artificial breeding). |
10. Explain how Linnaeus’ classification scheme fits Darwin’s theory of evolution by natural selection.
Linnaeus grouped organisms by shared traits, which aligns with evolutionary relationships—species that appear similar often share a common ancestor. |
11. Describe the three inferences Darwin made from his observations that led him to propose natural selection as a mechanism for evolutionary change.
Observation 1: Organisms produce more offspring than can survive.
Observation 2: There is heritable variation among individuals.
Inference: Those with advantageous traits survive and reproduce, passing those traits on. |
12. Explain how an essay by the Rev. Thomas Malthus influenced Charles Darwin.
Malthus argued populations grow faster than resources, leading to competition. Darwin applied this idea, concluding that only the fittest survive. |
13. Distinguish between artificial selection and natural selection.
Artificial selection: Humans breed organisms for desired traits. Natural selection: Nature selects traits that enhance survival and reproduction. |
14. Explain why an individual organism cannot evolve.
Evolution occurs at the population level as allele frequencies change across generations. An individual’s genes remain the same. |
15. Describe the experiments that supported Endler’s hypothesis that differences in life-history traits (look this up) between guppy populations are due to selective pressure based on predation.
Endler moved guppies from high-predation to low-predation environments and found brighter-colored guppies survived better in low-predation areas. This supported that predation selects for certain traits. |
16. Explain how the existence of homologous and vestigial structures can be explained by Darwin’s theory of natural selection.
Homologous structures (e.g., whale fins and human hands) suggest common ancestry.
Vestigial structures (e.g., human tailbone) are remnants of ancestral traits. |
17. Explain how evidence from biogeography supports the theory of evolution by natural selection.
Species in similar environments evolve differently based on geographic isolation (e.g., marsupials in Australia vs. placental mammals elsewhere). |
18. Explain the problem with the statement that Darwinism is “just a theory.” Distinguish between the scientific and colloquial use of the word theory.
Colloquial theory: A guess or speculation. Scientific theory: A well-supported explanation based on extensive evidence. Evolution is a scientific theory backed by fossils, genetics, and direct observation. |
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