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Transcript
History and Theory of Evolution Evolution Introduction • Definition: – Change in a population over time • Specifically: – Evolution is the frequency of heritable traits in population changing from one generation to the next Evolution Introduction • Allele = several variety of changes • Alleles code for traits to establish form or structure, physiology, or behavior • Descent = subsequent generations with modifications Evolution Introduction • Explains: – Ways organisms suited for environment – Shared characteristics of life (unity) • Genetic code – Diversity of life • Life became many different forms 2 Views of Evolution • Microevolution – Small changes over short periods of time – Supports improvements in existing species • Macroevolution – Small changes accumulating over long periods of time result in major changes – Supports the formation of new speices History of Evolution • Paved the way for Darwin’s thinking History of Evolution • Some Greek philosophers suggested life may change gradually over time • Aristotle (384 -322 B.C.) viewed species as fixed – Ordered all organisms based on complexity History of Evolution Classification • Carolus Linnaeus – Developed binomial nomenclature system of naming organisms • “nested” classifications system (not linear) – Opposed the idea of evolution Paleontology History of Evolution • Georges Cuvier – Studied fossils in strata • Fossils in older strata have changed from current life-forms • Some species appeared and disappeared – His explanation: catastrophism = events in past occurred suddenly • Boundary between strata represented a local catastrophe (ex. flood); area repopulated by immigration History of Evolution Geology • Charles Lyell – Came up with gradualism or uniformitarianism • Change is constant over time • Same process, same rate – Sediment deposition is constant – Catastrophes are common Pattern of Evolution History of Evolution • Erasmus Darwin – Grandfather of Charles Darwin – Life evolves as environments change Pattern of Evolution History of Evolution • Jean-Baptiste de Lamarck – Organisms adapt to their environments by acquiring traits – Changes in their lifetime • Disuse: organisms lost parts because they did not use them • Perfection with use and need: the constant use of an organ leads that organ to increase in size – Transmit new characteristics to next generation Lamarck • Observation of giraffes: – In order to reach higher vegetation, giraffes stretched their neck to acquire longer necks Using Darwin’s ideas: Giraffes born with longer necks survive better and leave offspring that will inherit their long necks Naturalist History of Evolution • Charles Darwin (1809 – 1882) • British naturalist (tried medicine and clergy) • Proposed evolution by natural selection – Differences in survival and reproduction in accordance to their interaction with environment Charles Darwin • Invited to travel around the world in the HMS Beagle – 1831-1836 – Made many observations of nature Robert Fitzroy Voyage of the HMS Beagle Observing the origin of the fauna on the Galapagos Observations • Succession of Types – Current species resemble fossils in same area Why should extinct armadillo-like species & living armadillos be found on the same continent? Glyptodont fossils are also unique to South America. Observations Mylodon (left) Giant ground sloth (extinct) Modern sloth (right) “This wonderful relationship in the same continent between the dead and the living will…throw more light on the appearance of organic beings on our earth and their disappearance from it, than any other class of facts.” Observations Observations • Darwin collected and found birds on Galapagos islands – Thought they were very different kinds – However…14 birds species were different types of finches – Only one species of finch found on the mainland How did one species of finches become so many different species now? Observations Descendant species Ancestral species Observations • Correlation of species to food source Seed Eaters Flower Eaters Insect Eaters Darwin’s Finches • Found differences in beaks – Associated with different foods Darwin’s Finches • Conclusions: – Small populations of original South American finches landed on islands • Variation in beaks enabled individuals to gather food successfully in different environments – Over generations, population of finches changed anatomically and behaviorally • Accumulation of advantageous traits in population • Emergence of different species Darwin’s Finches • Differences in beaks: – Successfully compete – Successfully feed – Successfully reproduce • Pass on successful traits – Natural selection More observations • Correlation of species to food source Whoa, Turtles, too! More Observations Many islands also show distinct local variations in tortoise morphology …perhaps these are the first steps in the splitting of one species into several? Darwin’s Return • Returned to England in 1836 – Wrote papers describing observations – Wrote his theory of species formation in 1844 • Instructed his wife to publish his ideas after his death • Reluctant to publish but did not want his ideas to die with him But… • 1858 = Darwin received letter from Alfred Russel Wallace • Wallace published article similar to Darwin’s unpublished idea of natural selection – Asked Darwin to evaluate his ideas and pass it along for publication It was time!!! • Became a race of who will publish first and what will be better accepted • Wallace published his article on “The Tendency of Varieties to Depart Indefinitely from the Original Type” (1858) • Darwin published “The Origin of Species by Means of Natural Selection” (1859) Patterns of Evolution • 3 types of evolution (describing organisms in relation to one another): 1. Divergent (adaptive radiation) = similar organisms become increasingly different because of different types of environments Patterns of Evolution 2. Convergent evolution = different organisms become increasingly similar because of similar types of environments Patterns of Evolution 3. Coevolution = two nonrelated species change because of close interaction • Predator-prey (disease & host) • Competitive species • Mutualism (pollinators & flowers)