The History of Evolution

History of Natural Theology Classical Greek philosophers had ideas about the natural evolution of life Plato (427-347 B.C.) believed there were two worlds. A real world which was perfect and an illusionary world that was imperfect. He did not believe in evolution. His student Aristotle (384 -322 B.C.) believed that all forms could be arranged on a ladder or scale called the “scala naturae” Each form of life had an allotted rung on the ladder. Belief prevailed for 200 years.

Carolus Linnaeus(1707- 1778) Father of taxonomy. Taxonomy is the branch of biology concerned with naming and classifying organisms. Came up with Kingdom, Phylum, Class, Order, Genus, Species. However he believed there was no evolutionary kinship between them.

Georges Cuvier(1769-1832) Paleontologist. Documented and recorded the succession of fossils in sedimentary strata in the Paris Basin. Found deeper and older fossils to be dissimilar. New species appear and older species disappear. Advocated catastrophism. Species killed off by catastrophes and recreated.

James Hutton(1726-1797) Scottish geologist. Proposed gradualism . Profound changes are due to gradual changes over a long period of time due to natural processes occurring within the Earth’s crust.

Charles Lyell (1797-1875) Proposed uniformitarianism. The idea that geological processes have not changed over time and are at work. Suggested the earth was a lot older than the previously thought 6000 years. Processes persisting over long periods of time can accumulate to substantial change.

Charles Lyell

Jean Baptist Lamark Was in charge of an invertebrate collection at the Natural History Museum in Paris. Noticed that species changed over time. Proposed that phenotype can change in response to environment changes and those new characteristics were passed on to the offspring. First idea that adaptations occur in response to the environment.

Jean Baptist Lamark

The Darwinian Revolution Charles Darwin(1809 -1882) was born in Shrewsbury, England. Wanted to be naturalist but was sent to medical school in Edinborough at 16. He dropped out and went to Christ College at Cambridge University and became a clergyman. Back then most naturalist were clergyman. Viewed the world as natural theologists. The view that each species was newly designed and non-evolving.

Darwin 1875

Reverend Robert Henslow Botany professor at Cambridge. Darwin was his protégé At age 22 he was recommended to join Captain Robert Fitzroy on the H.M.S. Beagle to sail around the world. The primary mission was to chart the South American coastline. Darwin collected and observed the flora and fauna.

H.M.S. Beagle Voyage

Descent With Modification A Darwinian View of Life

The Galapagos Species unique although they most closely resembled South American species. Darwin’s finches possessed different beaks to accommodate different modes of eating. Darwin read Principles of Geology by Lyell and surmised that “old Earth” was inhabited by evolving species.

Darwin’s Finches

The Origin of Species Lyell and a collegue presented Darwin’s work Along with another British scientist by the name of Alfred Wallace. The paper was on the theory of “Natural Selection” which Wallace and Darwin came up with simultaneously. Darwin published “The Origin of Species” a year later.

Alfred Wallace

Darwin’s Observations Species had distinct South American characteristics. South American species that lived in the temperate regions more closely resembled the tropical species on the same continent than species that resided in the temperate regions on a different continent. South American fossils resembled South American species.

Observations That Lead Darwin to the Theory of Natural Selection All species have the potential to reproduce the maximum number of offspring. Populations remain stable (except for seasonal fulgurations. Resources are limited CONCLUSION Organisms compete for food.

Other Observations Organisms vary Organisms with suitable traits survive to reproduce. Gradual changes in a population occur and the population accumulates favorable characteristics.

Additional Evidence for Natural Selection Homology similarities in characteristics due to a common ancestor. Anatomical homologies similar structures, different function. Embryological homologies Similar structural development. Molecular homologies Basic machinery of RNA and DNA are similar. Biogeographic homologies Convergent evolution

Homologies Biogeographic homologies Endemic species. Convergent evolution - species that look similar but have no common ancestry. Divergent evolution – species that have common ancestry but evolve disparate characteristics. Fossil Record – the appearance of certain classes of vertebrates in the fossil record. Fish before amphibians

Homologous Structures

Convergent Evolution

Natural Selection Differential success in reproduction. Variation in populations and how they respond to the environment. The product of adaptation to their environment.

Descent With Modification

Cartoon of Darwin