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LAMARCK, WALLACE AND DARWIN Theories of Evolution LAMARCK (1774-1829) environment plays a role in evolution uses and disuse allows species to become better adapted to their environment structures that the species used becoming larger and stronger structures not in use becoming smaller and weaker inheritance of acquired characteristics each species becomes more and more complex through the process of acquired traits from parents adaptations to environmental conditions during the organism’s lifetime could be inherited by future generations new simple species are created by spontaneous generation LAMARCK (1774-1829) http://www.scienceinseconds.com/episodes/Lamarckian-Evolution MALTHUS published essay “Principle of Population” population sizes would increase exponentially if not limited population sizes are dependant on limiting factors such as food supply other environmental factors, such as accidents, war and disease help control population sizes populations experience a struggle for existence Malthus’ ideas had huge impacts on the development of Darwin and Wallace’s Theories of Natural Selection http://www.ask.com/youtube?q=malthus+video&v=QAkW_i0bDpQ WALLACE (1823-1913) can up with a theory for the mechanism of evolution within a few days with very little evidence send his theory to Darwin and the two theories were very similar pushed Darwin to publish his theory as Darwin wanted to be the first to publish http://www.nhm.ac.uk/nature-online/science-of-natural-history/biographies/wallace/ DARWIN (1809-1882) collected observations for 20 years on ananotomical differences within and between species, biogeography and fossil records published his theory of evolution (Theory of Natural Selection) in 1859 in the book “On the Origin of the Species” http://science.discovery.com/videos/galapagos-beyond-darwin-charles-darwin.html DARWIN (1809-1882) Darwin’s Observations there is variety between individuals within populations some of the variation among individuals is inherited by the offspring from their parents more offspring than can survive are produced every generation population size usually remains stable over time DARWIN (1809-1882) Darwin’s Inferences members of the same species compete with each other for survival in every generation, some individuals are more successful at surviving and reproducing than others successful individuals have more favourable adaptations and are more likely to pass their traits on to offspring survival and reproduction of individuals is not random individuals with the most favourable adaptations, those who are better as surviving and reproducing, are naturally selected as the individuals with more favourable adaptation produce more offspring than those lacking the favourable adaptation, the favourable adaptation will become more common in the population DARWIN (1809-1882) Darwin’s Theory of Natural Selection Natural selection preserves favourable variations within a population of organisms, while those that are injurious will eventually be eliminated. Survival of the Fittest phrase coined by Spencer to describe Darwin’s theory DARWIN (1809-1882) Darwin’s Finches - Example of Natural Selection DARWIN (1809-1882) DARWIN (1809-1882) Issues with Darwin’s Theories Resolution There are too many gaps in the fossil record. Where are the transitional species between major groups of species. Many adaptations are bizarre or unexplainable. There was no clear mechanism for the inheritance of variable traits. How can minor variations between individuals explain the appearance of complex features (eyes) and behaviours (mating dances). How can the existence of altruism be explained (where an organism sacrifices for the benefit of others). there are many transitional fossils, particularly of shelled marine invertebrates that fossilize well overall, fossilization is a rare event, and finding a significant proportion of fossils is unlikely, so it will always be a spotty and incomplete record many adaptations are being explained with supporting evidence, but it takes time and expertise it will never be possible to explain every adaptation of every organism, let alone prove that each explanation is correct modern discoveries in genetics mesh well with his work and make his ideas even more workable plausible sequences have been made for the evolution of many complex features such as eyes (which have evolved at least seven separate times) it can be seen why behaviours become more elaborate over time, especially if it involves mate selection and reproduction. most altruistic behaviour that has been studied occurs amongst relatives if fitness means passing on your genes, then helping your relatives is one way to do that, the price has to be carefully evaluated