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Transcript
The Theory (?) of Evolution What is evolution? Evolution - the change in the inherited traits (genes/alleles, geno/phenotypes) of a species over time • Evolution is the process that best explains why life exists the way it does on Earth Who came up with evolution theory? • The most famous explanation of evolution was made by Charles Darwin • Theory 1st published in ‘On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life’ Others helped… • Georges-Louis Leclerc, Comte de Buffon (1707 – 1788) • Noticed that some species look similar and may have a common ancestor • Postulated that the Earth was >6000 years old Others helped… • George Cuvier (1769 – 1832) • Father of modern paleontology • Noticed that deeper rock strata contained more dissimilar species • Species appear/disappear over time Others helped… • George Cuvier (1769 – 1832) • Proposed that Earth has experienced mass extinctions (“catastrophism”) • These events (floods, eruptions, meteorites, etc.) are visible in rock strata • Correspond to new species appearance Others helped… • Jean-Baptiste Lamarck (1744 – 1829) • 65 when Darwin was born • Compared current species with fossils • Observed that fossil series led to modern species • Postulated ‘theory of acquired characteristics’ • Species increase in complexity over time until achieving perfection Others helped… • Jean-Baptiste Lamarck (1744 – 1829) • Hypothesized that organisms would become better suited to their environment over time • Body parts that were used to cope with environmental conditions would get better (larger, stronger, etc.) eg. Lamarck’s giraffe • Giraffes stretched their necks to reach the foliage from tall trees • Over time this stretched neck condition is passed down to offspring • This theory was critical because it highlighted the idea that physical traits could be passed to offspring Darwin (1809 - 1882) • 1831 • 5 year voyage to South America on HMS Beagle • Darwin’s job was to collect/record data on rocks, plants and animals Darwin’s observations 1. The flora/fauna found on the journey were similar but distinct from those found elsewhere • Concept of biogeography ( the study of the geographic distribution of species & ecosystems over geological time) Darwin’s observations 2. Fossils of extinct animals are structurally similar and share a distribution pattern with modern animal versions Sloth Megatherium Armadillo Glyptodont Darwin’s observations 3. Galapagos species varied slightly between islands • eg. Finches throughout the Galapagos islands had beaks adapted to eating different types of food Darwin’s observations 4. Sexual reproduction results in variation within a species • Gregor Mendel’s genetics work wasn’t accepted until 1900 • Many people at the time, thanks for dog/plant breeding, knew that traits were somehow passed from parent to offspring Finalizing the theory • Darwin used these observations theorize how/why species change over time • Darwin and Alfred Wallace both popularized the idea that species change over time but could not explain how • Thomas Malthus had previously suggested that populations produce far more offspring than the environment can support • Darwin used this idea to postulate natural selection (survival of the fittest) Natural selection • Individuals with traits that help them survive (better fitness) in their environment are more likely to survive • Individuals who survive longer are more likely to reproduce and pass on their traits • Subsequent generations will exhibit the surviving trait more frequently Natural selection • FYI: Darwin used the word evolution once in Origin of Species (he called it descent with modification) • Natural selection does not always demonstrate progress (devolution is possible) Activity • Sample study: Lamarck vs Darwin