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I. Early Ideas on Origin of Species A. Genesis a. written around 1446 BC b. species are static; earth about 6000 years old B. Anaximander a. around 500 BC b. life began in the sea c. simpler organisms begat the more complex ones C. Aristotle (384-322 BC) - species do not change
D. Study of fossils (1700’s) - began to spur belief that Earth was very old E. Jean Baptiste Lamarck (1744-1829) a. early advocate of evolution b. “inheritance of acquired characteristics” “All knowledge that is not the real product of observation, or of consequences deduced from observation, is entirely groundless and illusory.”
II. Charles Darwin • A. Five year voyage on the Beagle • 1. Captain Robert FitzRoy • a. takes command after a suicide • b. a student of phrenology • c. a kidnapping “experiment” gone wrong • d. a hasty return to Tierra del Fuego for more “mapping” • e. naturalist needed (really a companion for the long journey)
2. Charles Darwin (1809-1882) a. studied to become a clergyman (Cambridge) b. interest in collecting plant and animal specimens c. botany professor recommended him for the Beagle
B. South America and Galapagos islands (1831-1836) 1. species well-adapted to their environment 2. species “resembled” mainland organisms 3. fossils more similar to modern South American species than to fossils on other continents
4. adaptation among finch species: a. beak size and shape b. influence feeding c. environmental conditions influence survivability (dry, wet)
C. Thomas Malthus (an economist) 1. Essay on the Principles of Population (1798) a. populations of organisms increase geometrically b. rate of reproduction too high to be sustained c. warning against human overpopulation 2. but in nature, this does not seem to occur 3. Darwin’s answer: death (selection) limits population numbers 4. This provided missing link for Darwin
D. Alfred Wallace 1. came to same conclusions while in Indonesia 2. published his findings along with Darwin (1858-59)
E. Darwin: On the Origin of Species by Means of Natural Selection 1. descent with modification 2. closely related species likely from common ancestor
Darwin’s Theory Hypothesis 1: Every organism has the potential to leave more than one offspring. Hypothesis 2: The number of individuals within a species remains fairly constant over time. Prediction A: If 1 and 2 are true, then not all individuals realize their reproductive potential. Hypothesis 3: Individuals within a species vary in terms of their traits. Hypothesis 4: At least some of these traits are inherited. Prediction B: If A, 3, and 4 are true, then some individuals are better suited for their environment, leaving more offspring. Their traits become more common.
Darwin’s Theory Better suited individuals have inherited those traits, and they pass them on to their offspring. Survival of the fittest = Reproduction of the fittest.