Fossils FOSSIL: Any preserved evidence of life from a past geological age, such as the impressions and remains of organisms embedded in sedimentary rock.

What can fossils tell us? Structure of organisms What they ate What ate them What type of environment they lived in PALEONTOLOGIST: a scientist who studies fossils.

The Fossil Record FOSSIL RECORD: all information about past life that can provide evidence about the history of life on Earth. The fossil record is incomplete, because not all organisms become fossilized after death. Over 99% of all species that have ever lived on Earth have become extinct. The Thylacine, or Tasmanian tiger, became extinct due to overhunting. The last of it’s kind died in 1933. These were carnivorous marsupials.

Types of Fossils A. Trace Fossils: marking left by an animal such as a footprint. C. Imprints: a thin object, such as a leaf, that falls into sediment & leaves imprint when the sediment hardens. B. Casts: minerals fill in space left by a decaying organism, making a replica.

Types of Fossils E. Mold: when an organism is buried in sediment and then decays, leaving an empty space. F. Amber-preserved and frozen fossils: an organism that was quickly trapped in ice or tree sap (amber).

Geologic Time Scale GEOLOGIC TIME SCALE: used by paleontologists to measure evolutionary time. Eras: The longest time periods (aside from eons) that are usually separated by environmental change, and thus the extinction or formation of species. Periods: subdivisions of eras

TIME -millions of years ago Geologic Time Scale ERA PERIOD TIME -millions of years ago CENOZOIC Quarternary 1.8-present Tertiary 6.5-1.8 MESOZOIC Cretaceous 145-6.5 Jurassic 208-145 Triassic 245-208

TIME- millions of years ago Geologic Time Scale ERA PERIOD TIME- millions of years ago PALEOZOIC Permian 290-245 Carboniferous 363-290 Devonian 410-363 Silurian 440-410 Ordovician 505-440 Cambrian 544-505 PRECAMBRIAN - All geological time prior to ~600 million years

PRECAMBRIAN ERA: Nearly 90% of Earth’s history occurred during the Precambrian. Simple anaerobic life appeared, followed by photosynthetic forms, which added oxygen to the atmosphere. Precambrian simply means “everything before the Cambrian Era”. There are actually three eras in the Precambrian: the Hadean, the Archaen, and the Proterozoic. The three eras are grouped together in what is known as the Precambrian Era.

PALEOZOIC ERA: (ancient life) Early on, the fossil record became rich with evidence of many types of highly diverse marine life. Fossils of trilobites are abundant!

Periods within Paleozoic Cambrian Period: First known animals began to evolve, such as jellyfish and sponges. Ordovician and Silurian Periods: Ancestors of modern octopi and squid formed. The first vertebrates appeared, among them being jawless fishes. LOTS of marine competition!! Overcrowded oceans…

Periods with Paleozoic Devonian period: Often known as “The Age of the Fishes”. Lots of marine competition; animals began to invade the land (the first being arthropods). Carboniferous Period: many insects evolved such as dragon-flies & cockroaches. Dominated by arthropods. The amniotic egg evolved, which allowed for more successful reproduction among land animals.

Periods within the Paleozoic Permian Period- A great extinction occurred both on land and on sea. No one knows exactly what caused this extinction. It is estimated 95% of all life forms perished during the Permian Period.