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Darwin's Voyage of Discovery
­­Evolution = the idea that species change over time, specifically their gene frequencies
­­Before Darwin's theory, 2 main ideas:
1. Species are fixed or unchanging
2. Earth is <10,000 yrs. old and relatively unchanging
Title: Mar 28­11:34 AM (1 of 14)
Darwin's Voyage of Discovery
­­Darwin constructed his theory of evolution using the observations and inferences he made on the trip as well as the information from other scientists.
1. Georges Buffon's study of fossils suggested that the Earth must be older than a few thousand years (and certain living species similar to fossil species).
Title: Mar 28­11:34 AM (2 of 14)
Darwin's Voyage of Discovery
2. Charles Lyell proposed that gradual, observable geologic processes (like erosion) explain the physical features on Earth and the Earth must be very old in order to have these features.
3. Jean Baptiste Lamarck proposed that life evolves/changes and species are not permanent.
­­his idea of adaptations: the use/non­
use of body parts determines if features passed on to offspring
­­"inheritance of acquired characteristics"
Title: Mar 28­11:34 AM (3 of 14)
Darwin's Voyage of Discovery
­­In 1831, Darwin, 22, boarded the HMS Beagle.
­­The Beagle's mission was to chart the S. American coastline
­­Darwin's mission was to study the natural phenomena along the way.
Title: Mar 28­11:34 AM (4 of 14)
Darwin's Voyage of Discovery
­­Darwin collected specimens and maintained extensive journals of his observations on the geologic, plant, animal, and fossil phenomena he encountered during his journey.
1. Fossils and species still living in S. Am. different than those in Europe = descended from a common S. Am. ancestor.
Title: Mar 28­11:34 AM (5 of 14)
Darwin's Voyage of Discovery
2. Observed earthquakes in Chile and saw that land emerged from underwater. Collected fossils from high in the mountains that were originally on the sea floor.
3. On the Galapagos Islands, he noticed that species changed as they inhabited new islands (organisms adapted to unique environment).
Title: Mar 28­11:34 AM (6 of 14)
Darwin's Voyage of Discovery
­­From the work of others and from what he observed, Darwin questioned the ideas of the time.
­­The slow processes of mountain building and erosion suggested that Earth was very old.
­­These slow processes caused tremendous change in Earth and organisms must also be subject to gradual changes.
Title: Mar 28­11:34 AM (7 of 14)
Darwin's Voyage of Discovery
­­After returning home, Darwin studied his findings from the trip:
1. Earth = ancient
2. Species change over time
­­He began to think about how species actually adapt to their environment.
Title: Mar 28­11:34 AM (8 of 14)
Darwin's Voyage of Discovery
­­Darwin needed further information to figure out this question, so he looked into artificial selection.
­­He noticed that breeders play the role of the environment: 1. Only certain individuals are able to reproduce
2. This produces change in a species over time (dog breeds)
Title: Mar 28­11:34 AM (9 of 14)
Darwin's Voyage of Discovery
­­Darwin read Thomas Malthus' essay on population growth:
1. Populations grow faster than the rate at which food supplies and other resources can be produced
2. This leads to human suffering (disease, famine, homelessness)
­­Darwin recognized that Malthus' ideas applied to all species: the production of more individuals than the environment can support leads to a struggle for existence.
Title: Mar 28­11:34 AM (10 of 14)
Darwin's Voyage of Discovery
­­Using the evidence from his trip on the Beagle, artificial selection, and Malthus, Darwin formulated his theory (2 main points).
1. Species today descended from ancestral species. ­­Descendants of the earliest organisms spread to various habitats where they accumulated modifications, or adaptations, to diverse ways of life. ­­This is called descent with modification (rabbits).
Title: Mar 28­11:34 AM (11 of 14)
Darwin's Voyage of Discovery
2. Natural selection is the mechanism of evolution.
­­A process by which individuals with inherited characteristics well­suited to to an environment leave more offspring on average than other individuals.
­­This outcome causes the population to change over time, resulting in adaptations.
Title: Mar 28­11:34 AM (12 of 14)
Darwin's Voyage of Discovery
­­Darwin had written up his findings by 1844, but he did not publish them! ­­Instead, he accumulated more evidence to support his ideas.
­­In 1858, another scientist, Alfred Wallace, came to the same conclusions as Darwin. Wallace sent Darwin a letter outlining natural selection.
Title: Mar 28­11:34 AM (13 of 14)
Darwin's Voyage of Discovery
­­Within a month, portions of Wallace's and Darwin's writings were jointly presented to the public.
­­About a year later, Darwin finally published his full findings and conclusions in The Origin of Species. This book established Darwin as the main author of evolutionary theory.
Title: Mar 28­11:34 AM (14 of 14)