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Unformatted text preview: Chapter 13- How Populations Evolve Biologists definition Evolution=the processes of change in the forms of life over earths history Never in the life of one individual Never by self-will Limited by inherent genetic variation 1) Charles Darwin and his theory a) Historical Context i) Concept of fixed or ideal species prevailed until 1700s (1) Aristotle ii) Buffon (mid-1700s): old earth, changed life forms iii) Erasmus Darwin (late 1700s, grandpa to Charles): proposed life improved over millions of ages from simple, minute forms iv) Lamarck (1809): present-day forms evolved from older forms (1) But wrong about how acquired characteristics v) Lyell (1830): Principles of Geology (1) Evidence that earth is extremely old (2) Major features in earth caused by small changes over vast time: gradualism b) What Darwin did i) Naturalist on HMS Beagle 1831-1836[13.4] (1) Visited South America, Galapagos Island, Australia (2) Studied and collected life, rocks, and fossils ii) Studied and Wrote in England for 23 years iii) Origin of Species in 1859 c) Darwins Observations i) Great geographic diversity of life ii) Distinct island species resembled nearby continental species, yet adapted (1) Ex- iguanas [13.5] (2) Galapagos finches [13.5] iii) Rock formations suggested very old earth (1) As Lyell wrote (2) Yet fossils in local areas resembled living species iv) For all life, reproduction far exceeds resources (1) Inspired by Malthus ideas about human populations: the poor and weak suffer the most v) Tremendous amounts of variation possible thru artificial selection [1.15] (1) Ex- cabbage, broccoli, cauliflower all on species (2) Ex- pigeons d) Darwins Theory i) Part 1: Descent with modification (evolution) = all life is related thru descent from a common ancestor in past (like a branching tree) ii) Part 2: Natural Selection (mechanism for evolution) (1) Observation #1- overproduction: (a) All organisms produce more offspring than needed to replace them (b) Most populations remain stable in size (c) Resources for life are limited (2) Inference #1- There must be a struggle for existence among individuals in...
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This note was uploaded on 03/27/2008 for the course BIOL 113 taught by Professor Any during the Spring '07 term at Texas A&M.
- Spring '07