What are fossils? Direct or indirect remains of organisms persevered in media such as sedimentary rock, amber, ice, or tar
Different kinds offossils… Whole Organisms Replacement Permineralization
Different kinds offossils… Imprint Trace Mold & Cast
How do Fossils support Evolution? Transitional Fossils Despite the rarity of fossilization, we have a wealth of transitional fossil data that conforms to phylogenetic trees of various species.
The Law of Superposition The higher up you go in an undisturbed rock stratum, the younger the rock layers become. Relative Dating: Fossils can be dated this way in relation to the age of the rock surrounding them! Newer Sediment Older Sediment
How old is the Earth??? • Radioactive Dating: Geologists use uranium to estimate the age of the earth at 4.6 billion years.
Radio Carbon Dating: • C14 is a radioactiveisotope of carbon that is produced in the upper atmosphere. • Plants get their carbon from the atmosphere, this is passed on to animals through the food chain. • The ratio of carbon-12 to carbon-14 at the moment of death is the same as every other living thing, but the carbon-14 decays and is not replaced. • The carbon-14 decays with its half-life of 5,700 years, while the amount of carbon-12 remains constant in the sample. • By looking at the ratio of carbon-12 to carbon-14 in the sample and comparing it to the ratio in a living organism, it is possible to determine the age of a formerly living thing fairly precisely.
How old is the Earth??? • AbsoluteDating: • 1. Relies on events in the geological record with very strong annual cyclicity • 2. Measuring decay of radiogenic isotopes (ie. Potassium 40- Aragon 40)