History and Development of Theory

A process by which modern organisms have descended from ancient organisms

and/or Any change in the frequency of an

allele in a given gene pool

One of the first theories of evolution in 1809

Convinced species were not “constant” Species change New species from preexisting species

Develops theory of evolution based upon two principles

Law of Use and Disuse The more an animal uses a part of its body, the stronger and better developed it becomes

The less used, the weaker and less developed it becomes

The Inheritance of Acquired Characteristics Belief that the acquired characteristics through “use and disuse” will be passed on to their offspring

Example: Giraffes long necks are the result of reaching for food when supplies at ground level run out

German biologist-August Weismann 1870’s experiment Cuts tails of mice through 22 generations!

(Weirdo!) Each generation mice are born with tails of

normal length

Modern genetics Genetics don’t change as the result of “use and

disuse” or other modifications to the body

“Godfather” of modern evolution Son of wealthy doctor Began studying medicine but didn’t like it

Desired to study nature- At 22 yrs. old. sails with British Naval vessel HMS

Beagle in 1831 Ship mission is to map out

S. American Coastline Acts as ship naturalist Voyage lasts 5 years

Consulted Charles Lyell’s book, The Principles of Geology

Details earth’s advanced age Documents how the earth is constantly, slowly changing

Darwin draws conclusion that animals might show this same kind of change over time

Makes excursions during trip Observes that many animals and fossils

at different places demonstrate similarities

Most significant observations made on Galapagos islands

Darwin noticed that many of the animals, insects and plants resembled those on the mainland but have their own unique adaptations

Assumes that this evolution occurred as a result of differences in current environment

Darwin’s Finches:

•Darwin sees differences in finch beaks based upon geographic location and the foods that are available in those areas

•Thick beaks used to break foods like nuts

•Thin beaks used to probe trees for insects

Examples of the different finch species throughout South America and the Galapagos

Returns to England in 1836 with thousands of different specimens for research

Will dedicate most of the remainder of his life to this work

Still does not have an explanation for how evolution occurs!

Darwin reads essay by economist/mathematician Thomas Malthus “An Essay on the Principle of Population”

Malthus forsees social problems based upon exponential population growth and non-exponential food production

Says human population will have to be decreased via war, famine and pestilence (i.e., disease)

This theory helps form the basis of Darwin’s work on Evolution

1838-Darwin sees parallels in Malthus’s essay in the animal kingdom

Nature is the determining force Animals who have “favorable

variations” to the environment flourish and pass on their good genetics to offspring

Gene pool is altered = Evolution

Darwin continues research for 20 years Does not publish any work Receives essay from Alfred Russel

Wallace, English naturalist Essay tells of Wallace’s agreement

w/Darwin 1859-Finally publishes research as well

as Wallace’s paper

Darwin’s book creates firestorm of criticism from creationists

Book supports every theory with examples from Darwin’s years of research

Outlines 6 main points of evolutionary theory

Overproduction Species overproduce offspring Greater chance of survival

Competition All life competes w/one another for

space, food, etc. Variation

Even within species, there are differences in characteristics

Adaptations A favorable genetic change that

increases likelihood of survival Passed on to offspring

Natural Selection Nature determines who survives or not Survival of the fittest

Speciation Favorable adaptions add up in a species Eventually forms a new species

Homologous Structures

Vestigial Structures

Divergent Organisms have a common ancestor and have evolved separately from one another

Tend to have different characteristics

Example: Primates and Humans

Homologous Structures

Convergent Organisms have a common ancestor and

have evolved separately from one another

Due to similar environments, these organisms develop similar characteristics

Example: Shark v. Dolphin

Analogous Structures

Structural Darwin’s Finches

Physiological Human Appendix

Behavioral Hens who sit on their eggs