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Evolution In A Nutshell
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I. The Darwinian Revolution
Began in the 19th century. 1831 voyaged on the HMS Beagle Only 22 years old
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I. The Darwinian Revolution
Traveled South America’s coastline Collected flora and fauna
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Brazil, Argentina, Tierra del Fuego, and Andes Mountains
Europe
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Temperate species were closer to tropical species of South America than temp. species of Europe
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Formed from volcanoes, off the coast of Equador
II. Galapagos Islands Formed from volcanoes, off the coast of Equador
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He collected 13 different species from the islands.
II. Galapagos Islands He collected 13 different species from the islands. They differed by beak size Diet decided
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Some occupied more than one island
Different niches Darwin began to realize the Earth was much older than expected.
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Lyell’s book Principles of Geology helped him to understand this idea.
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III. Focus on Adaptation
The finches were actually different species 1837 began the first notebook on the origin of species
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III. Focus on Adaptation
Origin of new species (speciation) and adaptations are closely related processes
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Two populations could be isolated (geographic/reproductive isolation)
Over time become new species
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This is what is believed to happen to the finches of Galapagos
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1840’s Darwin had formed his theory of natural selection
Wanted to make it more complete before publishing.
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Alfred Wallace Wallace’s theory identical but Darwin’s more complete
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Darwin finished The Origin of Species in 1859
Father of Evolution Darwin used the phrase “descent with modification”
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Proposing Natural Selection
Organisms produce more offspring than can survive. (Fish can lay millions of eggs) In any population, individuals have variation. (Fish may differ in color, size, and speed.)
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Individuals with certain useful variations survive to reproduce passing traits on to offspring.
Over time, populations may change in appearance.
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Natural Selection A mechanism for change in populations.
Useful variations reproduce (adaptive traits) Individuals w/out trait die (maladaptive trait)
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Darwin thought of life as a branching tree with multiple branches from a common trunk.
At each fork is a common ancestor to all evolutionary lines of descent branching from that fork.
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Species that are similar share a common ancestor at a recent branch point
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Less closely related species share a common ancestor at a earlier branch point
Most branches are dead ends since about 99% of all species that ever lived are extinct
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