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