Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
EVOLUTION Transformation of the Biological Paradigm Evolution • Charles Darwin • BUT, the history of Evolutionary Thought pre-dates Darwin considerably… The Aristotlean-Christian World View • Aristotle (350 BC) – Greek • Special Creation & Fixety of Species – Every creature has its place, and all have been created in a specific and perfect form by an omnipotent & omnipresent creator. – No change – each organism is created in its most ideal form. The Aristotlean-Christian World View • Aristotle observes life’s complexity & Suggests a “Hierarchy of Life”: Complexity The “scala naturae” The Aristotlean-Christian World View • Following Aristotle (and all the way up into the 1700’s), this is the unchallenged world view. • Taxonomy (Identification & Naming of organisms) centers around placing newly discovered species properly into the pyramid (Linnaeus). Naturalists begin to find problems • Some organisms were not fitting properly into the hierarchy. • Due to Variations – Viewed as imperfections of an idealized form. – Which characteristics of an organism are most important for placing it in the hierarchy? – How much variation should be viewed as normal within a species? Georges Louis LeClerc DeBuffon • • • • (1707-1788) Wrote a huge “Natural History” Observed much Variation. Suggested the possibility of “Descent with Modification” – As organisms descend through time, modifications of the basic form occur due to differences in environment, geographic isolation, overcrowding, etc. – Offered no mechanism for such modification. – Suggested the Earth was only 168,000 years old. Erasmus Darwin • (1731-1802) • Charles Darwin’s Grandfather • Physician – Examined the Anatomy of many organisms. – Found Vestigial Organs (non-functional). • Why would these be present in a perfectly-adapted organism? – Examined changes during development (Ontogeny). • Suggested some sort of “Common Descent” – Currently living organisms have descended from ancestors of similar (but slightly different) form. – Offered no mechanism for such modification. James Hutton • (1726-1797) • Geologist • Suggested “Gradualism” – Changes to the Earth occur gradually through continuous processes…the same processes that are occurring right now: • Erosion • Volcanic activity • Earthquakes Charles Lyell • (1797-1875) • Geologist (father of “modern Geology”) • Suggested “Uniformitarianism” – Following Hutton’s ideas, Lyell suggested that the rate at which geologic events occur is both slow and uniform (gradual). – The same processes are responsible for both past and present geologic events…the geologic processes occurring now have been occurring over many millions of years. – Leads to the conclusion that the Earth is very old – “many millions of years old”. Georges Cuvier • (1769-1832) • Zoologist. • Comparative Anatomy of bones & muscles. – Similarities in structure, despite function. • Fossils (impressions of dead organisms in rock). – Slight differences in fossil forms found in different rock strata (layers of different age). – Was firmly entrenched in the Aristotlean-Christian View, so introduced Catastrophism as an explanation. • Sporatic catastrophies in the Earth’s history killed off certain species – those not found currently. Jean-Baptiste de Monet de Lamarck • (1744-1829) • Naturalist • Examined Rock Stratigraphy. – Fossils from the oldest strata appeared simpler, while those from more recent strata appeared more complex. • 1st to fully support “Common Descent” and suggest a link between biological diversity and adaptation to the environment. • Proposed a mechanism… Jean-Baptiste de Monet de Lamarck • Suggested that CHANGE in organisms took place by “Inheritance of Acquired Characteristics”. – Characteristics acquired during an organism’s life were passed on to offspring. – Giraffe Necks became longer and longer as each generation stretched higher into the trees for food. • Problem… Jean-Baptiste de Monet de Lamarck • Lamarck’s hypothesis was never supported by experiments. • Why? … • An environmentally-induced phenotype cannot be passed on to the next generation…only genotype can! • Lamark’s mechanism has long since been DISPROVED, but he is still remembered for this mistaken hypothesis! Charles Darwin • • • • • (1809-1882) British Naturalist Supporter of the Aristotlean-Christian Worldview. Began science in Medical School at Edinburgh Became more interested in nature (birds particularly), and quit Medical School. • Enrolled at Christ’s College at Cambridge to become a priest…still more interested in nature (especially collecting beetles). Charles Darwin • Finished School and planned to start a church in the countryside. • Before graduation, though, he gained an avid interest in Geology. • Was invited by former professors to become a Naturalist aboard the HMS Beagle – a ship destined for a sailing trip around the world. Charles Darwin • 5 year voyage (1831-1836) • Lots of DATA! 1. Geologic • He saw first hand what Hutton had suggested (Gradualism), and agreed with Lyell’s premise that the Earth must be very old. • He examined many fossils – some resembling modern (current) organisms, but not exactly. – Saw the possibility for Descent with Modification (modern forms having descended from now-extinct forms), and for organisms changing over time. Charles Darwin …DATA 2. Biogeography • He found similar organisms in far-reaching places, but in similar habitats. – Suggested that organisms may be adapting to the same types of environment, despite the distance between them. • He found slight variations in organisms found in slightly different habitats (but separated from each other … Finch Bills, Tortoise Necks, etc.) – Suggested that a common ancestor gave rise to the different varieties, which each adapted to slightly different environments. Darwin’s Biogeography Emu (Australia) Rhea (S. America) Ostrich (Africa) Darwin’s Biogeography Charles Darwin • Returned from the voyage and…PUBLISHED! • Saw that adaptation to environment was indeed real, and eventually formulated a mechanism for it, but… – He did not want to jeopardize his scientific status, so didn’t publish it. • Along came Alfred Russel Wallace… Alfred Russel Wallace • • • • (1823-1913) Naturalist Studied and admired Darwin’s work. Wrote Darwin to see what he thought about a hypothesis regarding a mechanism for adaptation to the environment. • This hypothesis was virtually the same as Darwin’s (unpublished) ideas about how change could take place! Darwin & Wallace • 1858 -- Presented their hypotheses at a meeting of the Linnaean Society (London): "The Variation of Organic Beings under Domestication and in their Natural State" "On the Variation of Organic Beings in the State of Nature; on the Natural Means of Selection; on the Comparison of Domestic Races and true Species" Darwin • Later (1859) published his famous essay: “I have called this principle, by which each slight variation, if useful, is preserved, by the term Natural Selection.” - Charles Darwin, The Origin of Species