-
4.6 billion years ago Earth is formed
-Much of the Earth was molten because of frequent collisions with other bodies which led to extreme volcanism.
-by accretion from the solar nebula.
-no oxygen yet -
~Earth began about 3.8 billion years ago, initially with single-celled prokaryotic cells, such as bacteria.
~Multicellular life evolved over a billion years later. -
~Happened around 2.3 billion years ago.
~began producing oxygen by photosynthesis.
~Free oxygen is toxic to obligate anaerobic organisms, and the rising concentrations may have wiped out most of the Earth's anaerobic inhabitants at the time. -
~2.1 billion years ago
~Eukaryotes flourished as the environment became richer in oxygen, perhaps in part because of their more complex intracellular function.
~Some of the earliest known single-celled eukaryote fossils are acritarchs
~ -
~2.1 billion years ago
~Had oxygen levels remained high, but instead atmospheric oxygen fell again shortly afterward, and these life forms died out without influencing subsequent evolution. -
~300 million years ago
~Supercontinent that existed during the late Paleozoic and early Mesozoic eras.
~Much of Pangaea was in the southern hemisphere and surrounded by a super ocean. -
~175 million of years ago
~There were three major phases in the break-up of Pangaea.
~One rift resulted in a new ocean, the North Atlantic Ocean. -
~200 thousand years ago
~Homo sapiens evolved in Africa.
~Evolved behaviors that helped them respond to the challenges of survival in unstable environments. -
The Great Oxygenation Event was probably the first major extinction event. Since the Cambrian explosion five further major mass extinctions have significantly exceeded the background extinction rate. The most recent and debatably best-known, the Cretaceous–Paleogene extinction event, which occurred approximately 66 million years ago (Ma), was a large-scale mass extinction of animal and plant species in a geologically short period of time.
