History of Natural TheologyClassical Greek philosophers had ideas

about the natural evolution of lifePlato (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 RevolutionCharles 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 HenslowBotany professor at Cambridge.Darwin was his protégéAt 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

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The GalapagosThe Galapagos Species unique although they most closely Species unique although they most closely

resembled South American species.resembled South American species. Darwin’s finches possessed different beaks to Darwin’s finches possessed different beaks to

accommodate different modes of eating.accommodate different modes of eating. Darwin read Darwin read Principles of GeologyPrinciples of Geology by Lyell by Lyell

and surmised that “old Earth” was inhabited and surmised that “old Earth” was inhabited by evolving species.by evolving species.

Darwin’s Finches

The Origin of SpeciesThe Origin of Species Lyell and a collegue presented Darwin’s work Lyell and a collegue presented Darwin’s work

Along with another British scientist by the Along with another British scientist by the name of Alfred Wallace.name of Alfred Wallace.

The paper was on the theory of “The paper was on the theory of “Natural Natural SelectionSelection” which Wallace and Darwin came up ” which Wallace and Darwin came up with simultaneously.with simultaneously.

Darwin published Darwin published “The Origin of Species” a “The Origin of Species” a year later.year later.

Alfred Wallace

Darwin’s ObservationsDarwin’s Observations Species had distinct South American Species had distinct South American

characteristics.characteristics. South American species that lived in the South American species that lived in the

temperate regions more closely resembled temperate regions more closely resembled the tropical species on the same continent the tropical species on the same continent than species that resided in the temperate than species that resided in the temperate regions on a different continent.regions on a different continent.

South American fossils resembled South South American fossils resembled South American species.American species.

Observations That Lead Darwin to the Observations That Lead Darwin to the Theory of Natural SelectionTheory of Natural Selection

OBSERVATIONSOBSERVATIONS All species have the potential to reproduce All species have the potential to reproduce

the maximum number of offspring.the maximum number of offspring. Populations remain stable (except for Populations remain stable (except for

seasonal fulgurations.seasonal fulgurations. Resources are limitedResources are limited CONCLUSIONCONCLUSION Organisms compete for food.Organisms compete for food.

Other ObservationsOther Observations Organisms varyOrganisms vary Organisms with suitable traits Organisms with suitable traits

survive to reproduce.survive to reproduce. Gradual changes in a population Gradual changes in a population

occur and the population occur and the population accumulates favorable accumulates favorable characteristics.characteristics.

Additional Evidence for Natural SelectionHomology 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

HomologiesBiogeographic 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 SelectionDifferential 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