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Biology 11 Mrs. Garrison EVOLUTION OF ORGANISMS OVER TIME HISTORICAL PERSPECTIVE Concept of evolution, or change, of plant and animal species over time is not Fossils – 1600, 1700 & 1800s – views of the church During late 1700’s, however, geologists (primarily in England) were paving the way for a comprehensive scientific theory on the origins of modern species James Hutton (1785) – Theory of UNIFORMITARIANISM Charles Lyell (1830) – age of earth must be in millions of years, not thousands William Smith (1769-1830) – surveyor First systematic study of fossils **SO WE SEE AN EARTH SURFACE BUILT LAYER BY LAYER OVER COURSE OF TIME & MOLDED BY SLOW PROCESSES OF NATURE BIOLOGISTS WERE NOT SO READY TO CHANGE, HOWEVER Among first to suggest that species might undergo changes over time: Buffon – Erasmus Darwin (Charles Darwin’s grandfather) – First person to work out systematic theory of evolution of species: Jean Baptiste Lamarck – 1801 –French Biologist INHERITANCE OF ACQUIRED CHARACTERISTICS Predominate view in early 1800’s was that of Cuvier (1769-1832) – --excellent understanding of fossils --staunch opponent of idea of change in species proposed theory of CATASTROPHISM NATURAL SELECTION Charles Darwin - born 1809 studied for medicine & clergy, not inclined towards either always enjoyed collecting specimens & observing habits of living org's age 22 (1831) - jumped at invitation to become naturalist aboard HMS Beagle during a 5-yr. voyage around the world HMS Beagle traveled from England down east side of South America, up west side of S.A., across Pacific to New Zealand & Australia, across Indian Ocean, around Cape of Good Hope & back to England --major undertaking was to chart coast of S.A. While there Darwin would spend hours collecting living & fossil specimens, & observing behavior of local species Darwin was impressed by the sheer # of diff. spp. Darwin had read Lyell's book & the idea of a gradually changing physical environment made good sense. Back at home, Darwin looked at the evidence and began to see a pattern that might dev. if spp were to change over time along with the changing environment Struggling with a possible mechanism, the answer became clear after reading Thomas Malthus' "Essay on the Principle of Pop." Malthus had written that pop's increased at geometrical rate, eventually running out of food & space Darwin recognized a tremendous amount of variability within a given spp & he brought this and Malthus' theory into play in his THEORY OF NATURAL SELECTION, which provided a plausible mech. for the change in a spp over time: 1) 2) 3) 4) 5) THUS, THE ENVIRONMENT "SELECTS" FOR THOSE ORG'S WHICH ARE BEST SUITED TO IT (NATURAL SELECTION) An org. is only best fit for that particular environment – --Thus, spp will slowly change as environ. selects for those members of pop. which are suited to the environmental changes. --If a spp doesn't change to fit environ, it will die out. --Eventually, the new spp may be very diff. from the original spp. Evolution does not cause change in individual org. but rather in a species over time - takes many generations. ALSO, natural selection does not create new traits. New traits originate by chance and environment selects for or against them AND natural selection does not create whole new, intricate organs all at once -- each step is a minute change Darwin's theory of NATURAL SELECTION was essentially worked out in 1838. HOWEVER, for next 20 years he worked on it (between bouts of illness), wanting it to be perfect Alfred Russell Wallace – Today we know about DNA, chromosomes and genes as the hereditary material. We recognize that changes in outward traits are due to chance changes (MUTATIONS) in the genetic material and also new combinations of traits due to sexual reproduction - that is, an offspring will receive traits from 2 parents in a combination never before realized. Darwin did not know about genes & chromosomes, but he recognized that the traits org's pass on must be inherited, not acquired, as Lamarck thought. ADAPTIVE RADIATION On Galapagos Islands, Darwin found 13 diff. spp of finches now believed to have arisen from one single pair or pregnant female from S.A. mainland