EVOLUTIONARY THEORY Evolution affects EVERY living thing All life is descended from the Original Life Form: Ur-slime DARWIN figured out how it could happen Had 100 years of precedents Natural History Hobby of rich men studied flora (plants) and fauna (animals) from other continents Age of Discovery By 1700 keeping track was a problem Gave flora and fauna European names in Latin Swedish botanist: Carolus Linnaeus (1717-1778) Systema Natura 1758 Hierarchic arrangement of all life Genus and Species (God s plan) Fixed and permanent immutable species classified by similarities in structures used by others to indicate biological relationships Linnaeus was NOT pleased One of the people thinking and writing about biological relationships: Charles DARWIN s grandfather And LAMARCK
LAMARCK (1744-1829) His idea: ANIMALS NOT FIXED, but CHANGE in RESPONSE 2 to the NEEDS of life in a particular ENVIRONMENT He thought: ACQUIRED CHARACTERISTICS could be INHERITED WRONG! He thought: ANIMALS change appearance because of adaptation to environment and pass that adaptation on to offspring WRONG! Stretch Longer neck Pass on to offspring NO WAY Some good things abut LAMARCK: -popularized thinking about animal evolution -saw that ENVIRONMENT is important -LIVING THINGS survive because they possess BIOLOGICAL FEATURES that permit them to exploit a particular set of ENVIRONMENTAL resources That is: ANIMALS ADAPT AND CHANGE BECAUSE of the ENVIRONMENT
CUVIER (1769-1832) Father of Anatomy 3 Workmen brought bones from quarry EXTINCT life forms Problem for Cuvier- he believed life forms were fixed and immutable Explained EXTINCTION with idea of CATASTOPHISM Series of catastrophes destroyed the fixed and unchanging life forms, then God created new forms (that were fixed and unchanging) until the next catastrophe The understanding of life on Earth was based on Plato Ancient Greeks idea: The Great Chain of Being The universe composed of a continuous series of formsgradually grade into the next higher form The Earth is full no room for anything new WRONG! Something good about Cuvier: -saw animals become extinct -got rid of idea of Great Chain CHARLES LYELL (1797-1875) Darwin didn t believe in Cuvier s Catastrophism because of Lyell Lyell geologist - said Earth s physical features were a result of nature operating in a UNIFORM manner (slowly) UNIFORMITARIANISM - earth is unchanging - time scale is big, earth is OLD, millions (billions) of years old So there is time for evolution to occur Refuted: Bishop Usher (counted generations in the Bible) Creation in 4004 BC Lyell published Principles of Geology in 1830
CHARLES DARWIN (1809-1882) When he left on the Beagle he believed in the fixity of species What he found altered his views 4 South America- fossils of extinct animals Earthquake (changes in earth due to natural forces) Galapagos Islands Large tortoises- vary from island to island Finches- 14 different species DIFFERENT BEAKS- DIFFERENT NICHES Radiated to fill all niches
FINCHES showed that the ENVIRONMENT shaped 5 the physical features of an animal species - ADAPTATION But HOW? (the big question) Finches modified their appearance over time- all descended from ancestral finch from South America But HOW? Darwin began to study domesticated animalsnoticed variation within a species Could variation be connected to adapting to the environment? But HOW? (How does SELECTION operate?) MALTHUS (1766-1834) Essay on the Principles of Population population size kept stable ->more individuals are born than survive to reach maturity (# of adults remains constant) Darwin already knew selection operated MALTHUS was the key to how! DARWIN S big breakthrough: -variation in individual physical features DETERMINES survival -some individuals are better adapted to the environment -those with favorable variations survive and reproduce BETTER ADAPTED INDIVIDUALS are more likely to SURVIVE and (most importantly for evolution) REPRODUCE Spencer (Sociologist): SURVIVAL OF THE FITTEST Darwin (Biologist): REPRODUCTION OF THE FITTEST called it Natural Selection Natural Selection operates on INDIVIDUALS, but it is the POPULATION that evolves
Darwin published On the Origin of Species in 1859 6 1-All species are capable of producing offspring faster than the food supply increases (Malthus) 2-Individuals vary 3-In the struggle for existence, those with favorable variation SURVIVE and REPRODUCE 4-Thus, favorable variation is passed on to the next generation 5-A long time span produces changes in a species, even NEW species THAT S HOW NATURAL SELECTION operates NO creation by design NO progression to a superior form Darwin figured this out by 1830 s -collecting data to support it -hated conflict - arranged to publish posthumously but in 1858 received a paper from WALLACE (1823-1913) like Darwin - was a natural historian, traveled widely thought about succession of species - read Malthus, then had malarial fever FLASH: positive checks to increase Best adapted survive, less well adapted perish Wrote essay - sent it to Darwin JOINT PAPER read before the Linnaean Society in 1858 (by Huxley) Then Darwin published Origin of Species in 1859 Descent of Man in 1871 Science never the same Couldn t figure out: HOW transmission of traits operated p.s. If only he read his mail
NATURAL SELECTION in action INDUSTRIAL MELANISM Manchester, England 7 2 forms of Moths: light and dark trees with lichen are light trees with no or dead lichen are dark If no pollution lichen lives, better to be a light moth If pollution, lichen dies, better to be a dark moth Because BIRDS eat moths off the trees Industrialization created pollution that caused lichen to die FOR NATURAL SELECTION to operate: 1. trait must be important in selection 2. trait must be inherited 3. there must be variation 4. fitness must change as environment changes (FITNESS = REPRODUCTIVE SUCCESS) For example: It s not just how many offspring-it s how many survive to reproduce SWIFTS # of eggs -> 2 3 4 # of young raised successfully: 1.92 2.54 1.76 (# of eggs laid is an inherited trait)