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Explore the rich history of Earth through the geologic time scale, from Precambrian to Mesozoic eras, examining organic evolution, species diversity, environmental changes, and the rise and fall of ancient life forms. Learn about plate tectonics, natural selection, and the significant events that shaped our planet.
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Chapter 13 – Geologic Time 13.1 Evolution and Geologic Time
The geologic time scaleis a record of Earth’s history that shows events, time units and ages.
2. It is subdivided into smaller units based on: 1. The types of life-forms living at the time. 2. Geologic events occurring at the time.
3. Eras- largest – based on life-forms. Periods- divide eras – based on life-forms and geologic events. Epochs- divide periods- smallest amount of time.
4. Organic evolution – the change in life-forms through time.
5. Species- a group of organisms that normally reproduce only among themselves.
6. When 2 different speciesbreed their offspring are unable to reproduce. Tigon – male tiger + female lion Liger – male lion + female tiger Males are sterile in both species
Albert's Squirrel South Rim Grand Canyon Kaibab Squirrel North Rim Grand Canyon
7. Natural selection – organisms with traits that are suited to a certain environment have a better chance of surviving to reproduce. First proposed by Charles Darwin in 1836.
8. The main cause of evolution of new species is 1. changes to environments 2. competition with others for resources
9. The Earth process most responsible for changing environments is plate tectonics.
10. Endangered – when only a small number of members are living. 11. Extinct – when none of its members are living.
12. 3 ways humans contribute to extinctions. 1. destruction of habitat 2. competition for same food supply 3. overhunting
Precambrian - Longest geologic time unit in Earth’s history. Began: 4600mya (4.6bya) Ended: 570mya
2. Precambrian fossils are sparse because: • Rocks are deeply buried or eroded away. • Rocks have been changed by heat and pressure. • Early organisms were soft-bodied – no hard parts.
3. Cyanobacteria – bacteria + algae. They photosynthesize. Form stromatolites. Appeared: 3.5 billion years ago Take in: CO2 Release: O2
4. Cyanobacteria were important because: They changed Earth’s atmosphere by adding free O2 to the air. The ozone layer formed protecting organisms from UV rays. Single-celled organisms evolved into complex organisms.
Invertebrate- animal without a backbone. Appeared: near the end of the Precambrian. Ex: jellyfish, sponges, worms
Evolutionary advancement that marked the beginning of the Paleozoic: when organisms developed hard parts.
Paleozoic – “ancient life”. • Life-forms that were most abundant during the Paleozoic- ocean dwelling (marine ) organisms. Why? Warm, shallow seas covered most of the Earth. Ex: trilobites, brachiopods, cephalopods, crinoids.
Vertebrate – animals with a backbone. Appeared: Ordovician Period Ex: jawless fishes, bony fishes, reptiles, mammals
10. Amphibian – vertebrates that live on land but must return to water to reproduce (lay eggs). Appeared: Devonian Period Ex: frogs, salamanders
11. Reptiles – vertebrates that live entirely on land – eggs have a leathery or mineralized covering. Appeared: Late Carboniferous (Pennsylvanian Period) Ex: tortoises, snakes, lizards, crocodiles.
12. Appalachian Mountains formed at the end of the Paleozoic. 13.What marked the end of the Paleozoic? • Largest mass extinction in Earth’s history. • Formation of Pangaea.
All continents are • still together as Pangaea
