July 6 th, 1946

May 6 th, 1856

February 12 th, 1809

Origins of The Theory of Evolution By Means of Natural Selection

Early Years Oct 1825 – Attends medical school at University of Edinburgh; drops out Dec 1827 – Attends seminary at Cambridge

Voyage of The Beagle Dec. 27 th, H.M.S. Beagle departs from England Darwin frequently ill/spends time reading Charles Lyell’s Principles of Geology (1830)

Significant Discoveries 8/13/1833: Finds fossils of giant sloth in Brazil 2/20/1835: Observes earthquake in Chile 1/16/1836: Observes platypus in Australia 8/19/1836: Observes volcano in Terceira

Galapagos Sept. 16 th, 1835 Observes diversity of tortoises, birds, lizards and barnacles on different islands in the archipelago

Return To England Oct. 2 nd, 1836 – H.M.S. Beagle returns to Falmouth, England Receives word from John Gould that his collected finches are same species, despite varied anatomy

How could same species have such different anatomy?

Adaptive Radiation “Descent With Modification” From one ancestral species, other forms have diverged to match the particular characteristics of their surroundings Species are changing over time, the changes being selected by nature.

What are the origins of this theory of evolution?

Georges de Buffon 1788 publishes Historie Naturale First to suggest that the Earth is older than 6,000 yrs old and that organisms have changed during that time

Jean Baptiste Lamarck 1801 publishes Theory of Inheritance of Acquired Characteristics Frequently contrasted with Darwin, although Darwin was an advocate of several of Lamarck’s ideas

Acquired Characteristics Law of “Use or Disuse” If environment changes, only some organisms will be capable of changing their phenotype to survive Those changes in phenotype will be directly passed on to offspring and they will be born with the altered trait in place

Charles Babbage Charles Babbage- inventor of first calculator Advises Darwin that all aspects of nature are controlled by laws Foundation of Darwin’s belief that transmutation applies to all lifeforms

Charles Lyell Charles Lyell continued discussion with Darwin about changes in geology of Earth Foundation of Darwin’s belief that as environment changes so must organisms

Sir John Sebright Wrote book The Art of Improving Breeds about artificial selection Foundation of Darwin’s belief that nature could also select for various phenotypes

T.H. Malthus Thomas Malthus- contributes idea of iron law of nature Foundation of Darwin’s “struggle for existence” Nature selected individuals through their fitness/ability to survive this struggle

1842- Down House

Thomas Huxley Meets and becomes close friend and advocate of Darwin Acts as the “face” of Charles Darwin, espousing his ideas at meetings of scientific societies

Alfred Wallace June 1856 – Charles Lyell sends Darwin a letter from Alfred Wallace On the Law Which Has Regulated The Introduction of New Species Came up with ideas while convalescing from malaria in South America, reading Charles Lyell

The Secret Is Out June 18 th, 1858, Wallace sends Darwin letter describing “natural selection”, “struggle for existence” and”transmutation” July 1 st, 1858, Darwin goes public with his theories

Origin of Species November 2 nd, Darwin publishes On the Origin of Species By Means of Natural Selection

What does the book actually say? Does not describe the origin of species, rather it only discusses changes in already existing species Does not use phrase “survival of the fittest” First five versions of book did not use word “evolution” Does not describe descent from apes

Descent of Man 1871-Darwin publishes Descent of Man Darwin dies on April 19 th, 1882 April 26 th, 1882 buried with much public interest in Westminster Abbey between Herschel and Newton

Darwinian Tenets Populations will always overproduce, hence all populations have inherent competition for resources Within all populations, there is variety The environment can and does change randomly Only some organisms will be able to survive AND reproduce in these new conditions (i.e. survival of the fittest)

How Does Nature “Select” For Different Variations? Variation Differences between individuals Variation Differences between individuals

Adaptation v. Variation Variation Differences between individuals Adaptations Differences between individuals that IMPROVE REPRODUCTIVE FITNESS

Modes of Natural Selection Stabilizing: Favors average phenotypes Directional: one phenotypic extreme favored Disruptive: Both extreme phenotypes are favored

Directional Selection & Industrial Melanism (Kettlewell Moth Experiment)

Transitioning Phenotypes

Stabilizing Selection

Disruptive Selection