What Evolution Is•Descent with
modification
•Change in genetic frequencies over time
•Change with inheritance
From http://evolution.berkeley.edu/evosite/evo101/IIntro.shtml
Historical Context of EvolutionPeople have always wondered about the origin of diverse life forms on Earth.
Aristotle and Scala Naturae
•Aristotle believed that there was a Divine Creator at the top of a ladder, and everything else descended from that being.
From http://www.ivirgil.it/set/Darwin/creazionismo.htm
Georges Cuvier•Observed changes
in fossil layers of rock
•Surmised that layers were different due to catastrophes (floods, ice ages)
What Lamarck Observed
•More modern fossils were found in upper layers of rock
•This led to the formation of more modern species
Use and Disuse •Body parts used to
get along in the environment get stronger and larger
•Those that aren’t used, deteriorate.
Inheritance of Acquired Characteristics
•Modifications acquired during an organism’s lifetime could be passed on to their offspring.
Dispelling the myths
•Neither of these things were possible because they were missing a very important component…
•Grew up very wealthy, educated
•Was a med student, then a divinity student
•Served as a naturalist for British government on the HMS Beagle
Darwin backgrounder
Development of Theory of Natural Selection
•Darwin observed 12 species of finches
•Noted differences in beaks and how that correlated to food choice
What Darwin noticed
•Organisms on the South American continent looked like those on the Galapagos but didn’t live anywhere else
•Was influenced by Lyell (Principia Geologica)
Natural Selection
After studying specimens he collected, analyzing data and reading an essay by Thomas Malthus, Darwin formulated a theory that explained how different species originated.
Tenet #4
•Organisms with favorable traits are more fit, thus they leave behind more offspring than those who are less fit.
In sum…•Natural selection occurs as a
result of interactions between the environment and the genetic variability demonstrated in living organisms.
•It is the result of differential reproductive success.
Artificial Selection
•Organisms with certain traits are bred repeatedly until population has only that trait
•Dog breeds are another good example
Other Evidence for Evolution
•There is other evidence that evolution has occurred: Anatomical MolecularFossil RecordBiogeography Fossil of Archaeopteryx, ancient bird
Vestigial Structures•Structures which are
smaller or reduced in size because they are no longer used/needed
•Whale pelvis
•Vestigial legs on snakes
•Human appendix
Embryological Similarities
•Presence of post-anal tail, pharyngeal gill slits indicates common ancestry
•What else does it indicate?
Molecular homologies
•Amino acid sequences among vertebrates have similarities
•What else is similar?
Top Related