The earth’s history
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Transcript of The earth’s history
THE EARTH’S HISTORYReview
Geologic time scale = record of earth’s history
Earth was created 4.6 Billion years ago. Its core was hot because as radioactive
material decayed over time, it generated heat.
4 billion years ago oceans formed as the planet cooled and water vapor condensed
3.3 billion years ago primitive algae formed
1.2 billion years ago multicellular organisms evolved
The earth 240 million yrs ago during Pangaea (when the land was all stuck together in one
mass)
200 million years ago the first mammals evolved
3 million years ago the first humanoids evolved
200,000 years ago both Neanderthals and Homo Sapiens evolved side-by-
side – Neanderthals went extinct Neanderthal vs. Homo Sapiens Scull
MOST of human history we were hunter gatherers
People who obtain food from what is available in nature by collecting plants, hunting animals, or scavenging animals.
This tends towards a nomadic or ever-moving life style
Early humans could have altered their environment by over hunting a species in one region to extinction – they think this happened to the giant sloth, saber-tooth tiger, and mastodons to name a few
Agricultural revolution 10,000 years ago
Led to: Population growth – more food supports more
people waste Buildings or primitive urbanization Slash and burn – changes natural ecosystem Habitat reduction ecosystem changes
reduction in natural resources Increase in number of domesticated animals Farmland Change in soil quality / loss of
fertility Flooding
Industrial revolution ~ 300 years ago
A shift from energy sources and society powered by humans or animals to fossil fuels such as coal or oil.
Improvements in quality of human life Consequences: Environmental and Social
pollution / climate change – reverse in the quality of life?
resource depletion social inequalities? loss of biodiversity resource depletion