Evolution In A Nutshell

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.)

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

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

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.

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

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