Evolution In A Nutshell I The Darwinian Revolution

Evolution In A Nutshell

I. The Darwinian Revolution n Began in the 19 th century. n 1831 voyaged on the HMS Beagle n. Only 22 years old

I. The Darwinian Revolution n Traveled South America’s coastline n Collected flora and fauna

n Brazil, Argentina, Tierra del Fuego, and Andes Mountains n Europe

n. Temperate species were closer to tropical species of South America than temp. species of Europe

II. Galapagos Islands n. Formed from volcanoes, off the coast of Equador

II. Galapagos Islands n. He collected 13 different species from the islands. n. They differed by beak size n. Diet decided

n. Some occupied more than one island n. Different niches n. Darwin began to realize the Earth was much older than expected.

n Lyell’s book Principles of Geology helped him to understand this idea.

III. Focus on Adaptation n. The finches were actually different species n 1837 began the first notebook on the origin of species

III. Focus on Adaptation n. Origin of new species (speciation) and adaptations are closely related processes

n Two populations could be isolated (geographic/reproductive isolation) n Over time become new species

n. This is what is believed to happen to the finches of Galapagos

n 1840’s Darwin had formed his theory of natural selection n. Wanted to make it more complete before publishing.

n Alfred Wallace n Wallace’s theory identical but Darwin’s more complete

n Darwin finished The Origin of Species in 1859 n Father of Evolution n Darwin used the phrase “descent with modification”

Proposing Natural Selection n Organisms produce more offspring than can survive. (Fish can lay millions of eggs) n In any population, individuals have variation. (Fish may differ in color, size, and speed. )

n Individuals with certain useful variations survive to reproduce passing traits on to offspring. n Over time, populations may change in appearance.

Natural Selection n A mechanism for change in populations. n Useful variations reproduce (adaptive traits) n Individuals w/out trait die (maladaptive trait)

n Darwin thought of life as a branching tree with multiple branches from a common trunk. n At each fork is a common ancestor to all evolutionary lines of descent branching from that fork.

n Species that are similar share a common ancestor at a recent branch point

n Less closely related species share a common ancestor at a earlier branch point n Most branches are dead ends since about 99% of all species that ever lived are extinct