Precambrian Era (put these events in order) Photosynthetic Cyanobacteria (blue-green algae) create oxygen gas which began to form our atmosphere Oceans form from water vapor released in eruptions and maybe comets that struck the Earth Earth forms Prokaryotes evolve- single celled organism that lack a nucleus Eukaryotes evolve. They have a nucleus and other complex structures Multicellular organisms evolve with soft bodies- examples such as jelly fish, coral, algae and segmented worms Hydrothermal vents, rich in nutrients, allow for chemical reactions to occur and create structures such as cells to form

Paleozoic Era (put these periods in order) Cambrian Period Devonian Period Ordovician Period Carboniferous Period Permian Period Silurian Period

Mesozoic Era (put these periods in order) Cretaceous Period Jurassic Period Triassic Period Cenozoic Era (put these periods in order) Quaternary Period Tertiary Period

1 st mammals 1 st Vertebrates on land- Amphibians Cambrian Explosion- Most major animal phyla are found in the fossil record Ozone layer formed 1 st Dinosaurs 1 st land plants 1 st Vertebrates- Jawless fish (lamprey and hagfish) Earth Forms Prokaryotes evolve- single celled organism that lack a nucleus Eukaryotes evolve- have a nucleus Put these events in order! 1 st reptiles 1 st Prehistoric humans