Descent With Modification: a Darwinian View of Life Chapter 22 BCOR 012 February 1, 2010

Darwin’s ideas challenged the prevailing view that the world was only a few thousand years old and that each kind of organism had been created individually in six days.

In 1645, Bishop Ussher of Ireland stated that the Earth must have been created on October 26th, 4004 BC.

Charles Darwin, 1809-1882

clergyman and naturalist Henslow’s sparrow Reverend John Henslow, 1796 - 1861 clergyman and naturalist

Captain of the H.M.S. Beagle Robert FitzRoy, Captain of the H.M.S. Beagle

The Voyage of the H.M.S. Beagle 1831-1836

Blue-black Grassquit, Volatinia jacarina

Darwin’s Beagle Voyage Observations: Geographic regions have distinctive floras and faunas Islands are centers of endemism Organisms are tightly adapted to the conditions under which they live

Charles Darwin in 1840

Alfred Russell Wallace 1823-1913

Charles Lyell, a geologist, presented the work of both men at a meeting of the Linnaean Society in 1858.

1st printing sold out in a single day! Darwin in 1859

Five premises underlying Darwin’s theory: Variability: Populations of organisms are variable Heritability: Some of the variable traits are passed from generation to generation Overproduction: More individuals are produced in a population than will survive to reproduce Competition: Individuals compete for limited resources Differential Survival: Those individuals better suited to their environment will leave more descendents than less well suited individuals. This is Natural Selection!

Evidence Supporting Darwin’s Views ...

Homology The equivalency of structures serving quite different functions provides evidence of common ancestry.

Variation under domestication: an entire array of dogs have been bred from a wolf-like common ancestor.

Darwin reasoned that if, under artificial selection, so much change could be produced in a relatively short time, than what a great amount of change should be possible over hundreds of thousands of generations!

Two main features of the Darwinian view of life: The diverse forms of life have arisen by descent with modification from ancestral species The mechanism of modification has been natural selection operating over immense spans of time

Evolution Explains Three Key Observations About Life: The good “fit” of organisms to their environment (adaptation) The unity ( shared characteristics ) of life The diversity of life

Charles Darwin, 1809-1882

On the Shoulders of Giants - Scientists Who Influenced Darwin

Geologist, chemist, naturalist, father of Hadrian wished to consolidate his boundaries. He visited Britain in 122 AD, and ordered a wall to be built from west to east "to separate Romans from Barbarians". JAMES HUTTON 1726-1797 Geologist, chemist, naturalist, father of modern geology GRADUALISM Hadrian’s wall

Charles Lyell, Hutton and Lyell’s influence on Darwin: 1797-1875 UNIFORMITARIANISM Hutton and Lyell’s influence on Darwin: The idea that slow processes operating over vast periods of time could produce great changes.

Georges Cuvier (1769-1832) recognized the restriction of distinctive fossils to particular geological series. Moreover, he observed a pattern in the change from level to level. Of the shells in the upper, more recent levels, he states, " the eye of the most expert naturalist cannot distinguish from those which at present inhabit the ocean." Forms of life recovered from successively more ancient strata were observed to become progressively more strange and "peculiar" (Cuvier 1817:13, 108-109). G. C. early recognized the phenomena of restriction of distinctive fossils — guide fossils — to particular zones, formations, or series and applied this tool in his stratigraphical studies. Moreover, he observed a pattern in the change from level to level. Of the shells found in the upper, more recent levels, he states that the "eye of the most expert naturalist cannot distinguish from those which at present inhabit the ocean." Forms of life recovered from successively more ancient strata were observed to become progressively more strange and "peculiar" (Cuvier 1817:13, 108-109).

Curator at the Natural History “… Nature has in favorable times, places, and climates multiplied her first germs of animality, given place to developments of their organizations, . . . and increased and diversified their organs. Then. . . aided by much time and by a slow but constant diversity of circumstances, she has gradually brought about in this respect the state of things which we now observe. Text of a lecture given by Lamarck at the Musée National d'Histoire Naturelle, Paris, May 1803 Jean Baptiste Lamarck 1744-1829 Curator at the Natural History Museum in Paris