Time Periods Flashcards
What are the four major divisions of geologic time in order ?
Precambrian
Paleozoic
Mesozoic
Cenozoic
How do geologist differentiate between time periods on the geologic time scale?
They categorize what type of species lived in each time period and the cataclysmic events that end each era.
What was the atmosphere like during the Precambrian time? What was the organism to promote life on earth?
The atmosphere was made out of gases like carbon dioxide, nitrogen, and water vapor. It was a place of turmoil because there was high radiations from the sun. The type of organism that helped promote life was the stromatolite, it used sunlight to produce food.(photosynthesis) thus creating oxygen and later on an ozone layer.
What is the importance of the ozone layer ?
It gives earth an atmosphere and creates almost like a shield from the harmful radiation and uv rays from the sun.
What is the difference between prokaryote and eukaryotes?
Prokaryotes are single celled and do not need O2 to survive.
Eukaryotes are multicellular and they do need O2 to survive
What are stromatolites and Cyanobacteria?
Stromatolites are organisms are a type of Cyanobacteria, they use the sunlight to produce food and photosynthesize. Photosynthesis releases O2 into the oceans and the air, therefore creating the ozone layer.
What was the Cambrian explosion ? And what era did it occur in?
It was a time period where many organisms were very abundant. And it happened in the Paleozoic era.
What happened at the end of the Paleozoic era ? What was the impact ?
It is thought that a meteorite destroyed about 90% of all the Paleozoic organisms. The impact was very large. It was a mass extinction
What happened at the end of the Mesozoic era and what was the impact ?
There was again something to extinct about 80 % of all life during this era. The impact was great but not as big as the Paleozoic impact.
What era is present day?
The Cenozoic era.
