Evolution Evidence from the past

Study of fossils Systematic study of all fossils==paleontology Fossil record consists of over 250,000 species of which <1% are living today Started in 18th century with Baron Georges Cuvier

Cuvier Notably revealed that most fossils were of extinct species and each layer of earth contained distinct species. Contrary to times==all fossils are from living species Simple organisms found at all layers but only the more complex were found at shallow depths Many species only found at one depth

Catastrophism Theory of Cuvier’s, that proposed global catastrophes caused widespread extinctions which gave way to newly created species Any problems with this? While it accounted for species only being found at one depth, it could not account for the increase in complexity at shallower depths.

Cuvier's terms Coined relative age and absolute age of fossil deposits Relative age: estimate of the age of a fossil by comparing it to other fossil specimens (according to depth) Absolute age : an actual estimate of the age of a fossil specimen (did not have means to do this at the time)

How old is the earth? Any guesses? Approximately 4.6 billion years old Scientists dated meteorites and used a method known as radiometric dating It involves Radioisotopes: atoms that undergo radioactive decay due to an unstable nuclear arrangement, which can be measured with a high degree of accuracy.

Radiometric dating Radioisotopes decay at a constant rate known as a half-life. The half-life is the time it takes for 50% of a parent isotope to turn into a daughter isotope. It is important to note that they are unaffected by temperature, moisture and various other environmental conditions, which makes it efficient.

Radiometric dating tools Some of the Primary Radiometric Dating Methods Parent Daughter Half Life(years) Dating Range(years) Items Typically Dated Uranium-238 Lead-206 4.5 billion Greater than 10 million Zircon, Uraninite. Uranium-235 Lead-207 704 million Potassium-40 Argon-40 1.3 billion Greater than 100,000 Muscovite, Biotite, volcanic rocks. Rubidium-87 Strontium-87 49 billion Muscovite, Biotite, Metamorphic or Igneous rocks. Carbon-14 Nitrogen-14 5,730 100- 40,000 Wood, Charcoal, Peat, Bone, Tissue,

Dating fossils Uses carbon-14 which has a half-life at 5730 years

Pre-darwinian ideas We know from last day that the fossil record provides evidence to the evolutionary puzzle. Geologists added the next piece… In 1795 James Hutton proposed the theory of actualism, which contrasted Cuvier. Actualism: a theory stating that the same geological processes occurring today also occurred in the past.

Pre-darwinian ideas In 1830 Sir Charles Lyell extended upon actualism, which his theory of uniformatarianism. This is the theory that the earth has and will always be undergoing a gradual, uniform, and constant state of change==same intensity as now. Conclusions from Lyell and Hutton: The earth must be incredibly old Dramatic extreme change could occur at what would seem to be a slow pace

Other key players Buffon: species could change over time, leading to new organisms Linnaeus: a few species have produced many new species through hybridization and interbreeding Grandpa Darwin: first detailed writings of evolution==everything arose from one source

Other key players de Lamarck: Environment key role in evolution Species must have the ability to adapt to changing conditions Did not believe in a single origin of life; instead species gradually become more complex Spontaneous generation==living organisms arise from non-living matter Acquired traits==changes in an individual as a result of interactions with the environment These changes could be inherited WRONG!!! Acquired traits cannot be inherited This paved the way for Charles Darwin

Pgs 513-518 Work: PP’s pg 515 End of Unit Project Reading Pgs 513-518 Work: PP’s pg 515 End of Unit Project For next class perhaps…debate regarding fossils: should fossils be donated or auctioned? And/or activity 11.2.1 page 534 of text