theme 5C- the history oif life Flashcards
what are the two major episodes in the history of life?
- evolution and speciation
- extinction- evolution and ecology
how old is the earth?
4.5 billion years old
how long ago did unicellular organisms appear?
3.5 billion ago
how long ago did multicellular organisms appear?
2.1 biliion years ago
how long ago did complex multicellular animals appear?
650 million years ago
what was the earths early atmosphere like?
little oxygen, reducing atmosphere
how was oxidation of the earths atmosphere prevented?
by removal of oxygen and other oxidizing gases/vapours
what type of habitat was still pockets of reducing environments in deep oceans?
sulfur bacteria and thermophiles
what happened during the archaean- proterozoic era (4 billion-510 million years ago)?
-prokaryotes, eukaryotes, multicellularity appeared
-the great oxygenation event
what is the great oxygenation event?
free oxygen accumulates in atmosphere about 2.5 billion years ago with a huge increase 850 million years ago
what is the evidence for the great oxygenation event?
-banded iron formations abundant between 2.5 and 1.8 billion years ago, decline after
-major changes in number of rock types formed after this event: hydrated and oxidized minerals
why was there such a long gap before oxygen atmosphere?
-long period of anoxygenic photosynthesis
-free oxygen reacted with ocean chemistry
-banded iron formations
what are banded iron formations?
oxygen was reacting with iron and sukphur to form these rocks
-between 2.5 and 1.8 billion years ago
why are mass extinctions significant to evolution?
-niches are cleared/ ecological opportunities available
-leaves dead clades walking- low diversity remnants of once diverse lineages
