4Most all divisions on this table are based on life-events that have occurred in the past Eras are divided based upon when dominant life forms existedCenozoic -- "Age of Mammals"Mesozoic -- " Age of Reptiles“Paleozoic -- " Age of invertebrates"Periods usually begin or end based on a beginning or end of a certain type of animalJurassic Period began when Giant Dinosaurs were abundant.
5Eras are the longest period of time on the table. Usually hundreds of millions of years (except Cenozoic)Periods divide Eras into smaller time periods.Epochs divide periods into smaller time periods.
15Inferences from fossil evidence Older fossils were simple in structure. As time passed life forms began to increase in size and complexityThe types of animals found in a location can indicate the type of climate that animal was living inCoral fossils indicate a tropical climate, marine fossils indicate shallow or deep water environment
17Look at ESRT and observe the bottom part of the column under life on Earth. Notice how animals begin as simple cellular animals and eventually change to soft bodied animals, then shells appear, then vertebrates, then reptiles and finally mammals. The process of change that produces new life forms is called EVOLUTION.
19VIF!!!! - Index Fossils existed in a relatively short period of time Index fossils are fossils that have the following characteristics:existed in a relatively short period of timeexisted over a large geographic areaMust be easily identified & abundantThey are useful in determining a period of geologic time within rock layers.If an index fossil is found in a layer of rock, the layer must have been formed in that index fossil’s specific period of existence.
21Key BedA single rock layer that has the same characteristics as an index fossilRelatively thin, widespread area, deposited rapidly, easy to identifyA volcanic eruption can produce a key bed because an eruption happens over a short period of time and usually covers a large areaA meteor strike can also produce a good key bed due to all of the debris that it scatters into the atmosphere.