The Historical Background of Evolution Theory Plato and Aristotle (BC) -”fixity of species”: species have always been, and always will be the same. -variations are imperfections of the overall species

“Scala Naturae ” -a way of organizing creatures and plants into a system. -man, and ultimately the gods, were at the top of the scale. -a fixed linear scale, from lowest life forms to the highest, representing degrees of perfection

God Man 4-legged creatures Birds Fish Flying Fish Aquatic Birds Stones Mushrooms Plants Monkeys A small portion of the Scala Naturae

This system did not represent the real world, it was made up (in Aristotle’s head). It has no way of accounting for things that are not “normal”. -big or small, different coloration, different patterns, etc. (Diversity!)

Carolus Linneaus -developed the first real taxonomy (classification) of organisms -he still believed that things did NOT change over time. -Systema Naturae (1735): a binomial classification system for organisms -reinforced the fixity of species.

Georges Cuvier Founder of comparative anatomy -based his beliefs on the fossil record, which shows many layers of sediment. -believed in “catastrophism”, where a series of catastrophes recreated everything anew each time.

Fossils : -Found in sedimentary rock (rock deposited as a type of sediment) -may be actual pieces of an organism ex: bones -may be imprints left by an organism ex: foot prints, shell prints

Index Fossils Fossils of known age, can be used to date sedimentary layers that they are found in. May also be used to date unknown fossils associated within a layer.

* * * Rock layer ( and fossil) of known age Unknown fossil, in same sedimentary layer as the index fossil

What kind of rock is this? Where would you find seashells? So, if you found this at the top a mountain… This rock comes from the yellow limestone layer near the very top of Mount Everest!

Law of Superposition Fossils associated with those sediments follow the same pattern. The Law of Superposition states that sediments found in upper layers are more recent than sediments found in lower layers.

A*A* B*B* Fossil A has to be newer (more recent) than Fossil B, because it is in a layer that was more recently created. OLDER

Mary Anning ( ) -”greatest fossilist ever known” -Discoverer of 1 st Ichthyosaurus

Also discoverer of the: 1 st Plesiosaurus, and 1 st Pterodactyl Plesiosaurus Pterodactyl

Mary Anning was partially responsible for the science of paleontology becoming recognized as a valid science. Until she made some of her discoveries, the science was regarded as a novelty, mostly involving collecting small fossils.

Paleontology:the study of prehistoric or extinct life forms. -each was followed by new flora and fauna. -proved that Earth was older than 6000 years, and had indeed been hit by a series of major catastrophes.

-Geologic history was a story of erosion and periodic catastrophe. Law of Superposition: If rock layers are undisturbed, lower layers are older than the layers above them. OLDER

James Hutton ( )- Scottish geologist, formulated the Theory of Geologic Uniformitarianism, which states: “Geologic processes now at work are identical to ones which have operated in the past, both recent and distant” Ex: Erosion now is the same as erosion 300 million years ago. (Same process, same rate)

Hutton’s “Unconformity”

Charles Lyell ( ) -First person to use index fossils as indicators of relative age. “Principles of Geology” (1830) -British geologist, showed conclusively that Earth is very old, and had changed form very slowly.

-Lyell originally supported the idea that species were unchanged, but later became one of Darwin’s biggest supporters. “Essay on the Principles of Population” -British economist, pioneer of modern population studies. Thomas Malthus ( )

Jean Baptiste Lamarck ( ) -no extinctions, just evolution to new types -basic assumptions: trends toward increased complexity “Philosophie Zoologique” (1809)

Lamarck’s Laws: Ex: Giraffe necks are long because they have been stretched to reach food. 2) These changes are passed on to offspring. 1) The law of use or dis-use. Structures enlarge or shrink based on their use.

Charles Darwin ( ) -Selection is based on variation within a population, not changes in individuals. -Darwin’s observations led him to a conclusion far different than Lamarck. -H.M.S. Beagle ( ) -British naturalist, sent on a voyage to map islands, and collect samples.

Darwin was heavily influenced by the other scientists work, particularly Thomas Malthus and Charles Lyell. Malthus said that populations would easily outstrip any food supply if not slowed somehow. He thought that some form of selection was necessary to lower population numbers.

Charles Lyell showed that the process which created the earth was very old, and was continuing today. He showed that the process acted very slowly and continuously, over immense time periods.

Natural Selection -the natural variation within a given population will allow some individuals to have traits which give them an advantage. -this advantage allows these organisms to pass their genes on, and therefore give the trait to their offspring.

Ex: A giraffe with a slightly longer neck (because of variation) will be able to eat more, and so be able to withstand more extremes in the environment (Drought). If the giraffe can withstand environmental pressures, it will be able to pass its genes for a longer neck on to its offspring.

Basics of Natural Selection 1)Variation exists within populations -seen in nature and in domestication. 2) Populations expand exponentially -lots of evidence for this in nature 3) There is always struggle for a existence. -for food, for space to raise young, etc.

4) Natural selection takes place -those with the most favorable traits for that environment are more likely to survive and reproduce. 5) Descent to the next generation -favorable characteristics are passed on to offspring, and eventually the frequency in the population increases.