Ch 10 Notes August 21, 2013 Ch 10 Geologic Time Scale Sec 1Life and Geologic Time Geologic time earth's history is divided into time units that make up the GEOLOGIC TIME SCALE. Time units on the scale are based on the appearance or disappearance of types of organisms such as trilobites, index fossils that lived during specific periods of time and over vast regions of the world.. Geologic Time is divided into 4 major subdivisions. A. Eons longest subdivision of time B. Eras marked by significant changes in types of fossils C. Periods based on types of existing life D. Epochs characterized by different regional lifeforms Organic Evolution Organisms have changed over time, most likely due to environmental changes. Darwin's theory of Natural Selection Species only reproduce with their own kind Survival of the fittest Artifical selection same as selective breeding where man chooses traits they want New species evolve from natural selection Trilobites have an exoskeleton with 3 lobes (this never changed); lived in oceans for more than 200 million years. Their eye position changed depending upon where they lived. Bodies and tails changed depending on environment. Changes in the trilobite exoskeleton can be attributed to changing environments and competition for survival. Continental collisions formed giant landmass Pangaea near the end of the Paleozoic Era. This caused sea levels to drop causing the extinction of trilobites. AutoSave 1 Ch 10 Notes August 21, 2013 Sec 2 Early Earth History Precambrain time from 4 billion to about 544 MYA (million years ago) Very little fossils from this time, probably because of 1.the rocks being deeply buried, 2.lots of heat and pressure and 3.the organisms were softbodied so they didn't become fossils. Cyanobacteria blue green algae. Earliest life form. Added oxygen to atmosphere by photosynthesis (contained chlorophyll).This made it possible the development of complex life forms because it help the atmosphere to have oxygen and an ozone layer. Invertebrates and Edicaran animals appeared late in Precambrian time. AutoSave 2 Ch 10 Notes August 21, 2013 Paleozoic Era Era of Ancient Life, 544 mya to 245 mya Cambrian Period 544 mya 1st Trilobites Ordovician Period 505 mya 1st Fish Silurian Period 440 mya 1st land plants Devonian Period 410 mya 1st Amphibians Missippian Period 360 mya 1st Reptiles Pennsylvannian Period 325 mya Permian Period 286 mya Many organisms with shells Amphibians evolved to survive in water and on land. Might have evolved from fish. They used gills or lungs. Reptiles evolved from amphibians to survive away from water. Appalachian Mountains formed because of plate collisions. Volcanoes very active Some organisms of the Paleozoic era were fish, trilobites, and reptiles. Most marine and land species became extinct at the end of the Paleozoic Era ( 245 mya). The change in environments that may have occurred at the end of the Paleozoic Era may have been caused by plate tectonics. AutoSave 3 Ch 10 Notes August 21, 2013 Mesozoic Era Era of Middle Life, 245 mya to 65 mya Triassic Period 245 mya Pangaea breaks into 2 large pieces, climate became drier 1st dinosaurs Reptiles most common animal Mammals 1st appeared (but different than today) Small, mouselike creatures Jurassic Period 213 mya 1st Birds They evolved from small dinosaurs Dinosaurs were dominant Cretaceous Period 145 mya Gymnosperms were dominant land plant (pine trees) Angiosperms were flowering plants w/seeds that have hard outer shells (oak tree) Some organisms during the Mesozoic Era were Angiosperms, reptiles, birds, and dinosaurs Mesozoic Era ended 65 mya with a mass extinction. AutoSave 4 Ch 10 Notes August 21, 2013 Cenozoic Era Era of Recent Life, 65 mya to today Tertiary Period 65 mya Paleocene Epoch 65mya Eocene Epoch 55.5mya Oligocene Epoch 33.7mya Miocene Epoch 23.8mya Pliocene Epoch 5.3mya Only Era with Epochs that have been given specific names. Quaternary Period 1.8 mya Pleistocene Epoch 1.8mya Holocene epoch 0.008mya Mountain building period with cooler climates (1st Ice Age) Alps and Himalayas Mountains were formed Mammals became dominant with many new life forms appearing after the dinosaur became extinct. Mammals evolved and some species became isolated as the continents continued to separate. Some organisms during the Cenozoic era were humans, reptiles, marine mammals, and birds. Humans also appeared about 400,000 years ago. AutoSave 5
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