Geological Periods Flashcards
1
Q
Cambrian Period
A
- rise in oxygen levels
- major diversification of life
- appearance of arthropods and chordates (which would later give rise to vertebrates) in fossil record
2
Q
Ordovician Period
A
- appearance of terrestrial plants in the fossil record (plants moved onto land)
- major extinction event at the end of this period
3
Q
Silurian Period
A
- “age of fishes” – fish start to develop jaws and become predators, dominate ocean
- increase in size and diversity of vertebrates
- expansion of terrestrial plants and arthropods (increasing oxygen levels in atmosphere)
4
Q
Devonian Period
A
- transition from fish to tetrapods
- Sarcopterygii “flesh-finned fishes” with bony fins that resemble the limbs of modern vertebrates, some had lungs, allow them to breathe on land and expand from ocean
- Huge radiation of life, especially onto land
5
Q
Carboniferous Period
A
- Stegalids in fossil record (transitional species from fish into arthropods) (Tiktaalik, Acanthostega, Ichthyostega)
- Huge explosion of terrestrial animals
- Huge forests - oxygen concentration almost doubled during this period
6
Q
Permian Period
A
- Age of amphibians, massive diversity –Temnospondylids in fossil record, likely to be earliest ancestor of all Lissamphibia (modern amphibians)
- The Great Dying, something like 90% of aquatic life and 70% of terrestrial life gone (massive drop in oxygen levels)
- Largest extinction event that we know of in the history of life on Earth
7
Q
Triassic Period
A
- start of Mesozoic Era, about a quarter of a billion years ago
- mammals, reptiles, amphibians – survivors of Great Dying
- froglike fossils, frogs widespread during this period
