Earliest life forms were influenced by: The forming atmosphere and oceans Volcanic activity Mountain building Life on land developed and flourished in tropical climates, but many life-forms became extinct at the end of the Paleozoic era (fish and reptiles still survived Influence of Catastrophes on Earth’s History

Mesozoic Era events: Reptiles, birds, mammals thrived Ended with a mass extinction (dinosaurs became extinct) Extinction theories include impact catastrophe with climate change Cenozoic Era events: Climatic changes- Ice Ages Species still thrived

Geologic Time Scale Divisions: Era, Periods, Epochs Geologic Time Scale divides Earth’s long history into units of time. Eras  Periods  Epochs ErasPeriodsEpochsDescription PrecambrianCambrian- 1 st period Earliest era Paleozoic Mesozoic CenozoicQuaternaryHolocenePresent Day OLDEST TO RECENT

Illustrate the vast diversity of life that has been present on Earth over time by using the geologic time scale. Geologic Time Scale- is a record of the major events and diversity of life forms present in Earth’s history. At the end of each era, a mass extinction occurred

Paleozoic Era: Mass extinction killed most invertebrates and amphibians Examples of Invertebrates: Trilobites, Brachiopods

Trilobites are an extinct group of arthropods with hard, jointed external skeletons, distantly related to crabs, scorpions, and insects. They are among the most familiar fossils of the Paleozoic Era, about million years ago. "The majority of trilobites were between three and ten centimetres long," notes Dave Rudkin, assistant curator of paleobiology at the Royal Ontario Museum in Toronto. "Their fossil remains are eagerly sought by amateur and professional paleontologists alike."

Brachiopods are marine animals that, upon first glance, look like clams. They are actually quite different from clams in their anatomy, and they are not closely related to the molluscs. They are lophophorates, and so are related to the Bryozoa and Phoronida. Although they seem rare in today's seas, they are actually fairly common. However, they often make their homes in very cold water, either in polar regions or at great depths in the ocean, and thus are not often encountered. There are about 300 living species of brachiopods. lophophorates

Mesozoic Era: The mass extinction at the end of the era caused the dinosaurs to become extinct

Cenozoic Era: New mammals appear while other mammals became extinct Diversity of life forms increased Flowering plants became most common Humans are part of the most recent period in this era