Life Over Time Lesson 4

The fossils shown are of marine organism. In which of the three rock layers would you expect to find fossils of an organism that went extinct before the marine organism evolved?

It was the bottom layer that you would expect for the marine organism to go extinct before it evolved because the deeper the layer, the older the fossil

List four major divisions make up the history of life on Earth in the geologic time scale?

1. Precambrian Time 2. Paleozoic ERA 3. Mesozoic ERA 4. Cenozoic ERA

What is one distinguishing feature of each of the four major divisions ?

1. Precambrian: Prokaryotes are the dominant life form in ocean. They live without oxygen 2. Paleozoic ERA: Lots of animals, sponges, corals, snails&trilobites) fish, sharks first appear. Plants and air-breathing animals went on land ( crowing insects & large salamanders 3. Mesozoic ERA: Age of dinosaurs first mammals & birds appear Cenozoic ERA: Present ERA humans appear

What is a fossil record?

All the fossils that have been discovered worldwide

What is extinction?

Death of every member of a species

What is a geologic time scale?

Division of Earth's history into manageable parts

How do atmospheric conditions near the beginning of Precambrian time contrast with the atmospheric conditions that are present now? Which organism is largely responsible for this change?

They contrast because in the Precambrian time there was little to no oxygen in the Cenozoic ERA we do. Cyanobacteria began to do photosynthesis and it was pumping out oxygen into the atmosphere

What is a fossil?

Trace or remains of an organism that lived long ago