Lecture 27: The Phanerozoic Biosphere Flashcards
What is the time span of the Phanerozoic era?
540 million years ago to now
What is Significant about the Cambrian era?
It is characterized by rapid evolution and diverse life
What is Cambrian Explosion?
The rapid explosion of life during the Cambrian era
What are the three broad categories of things generally accepted to explain the cambrian explosion?
- Environmental
- Developmental
- Ecological
What is the Environmental Explanation for the Precambrian Explosion?
Oxygen levels in the ocean increased so that life forms could evolve. Or, levels of calcium increased making it possible for sea organisms to build shells due to continental erosion
What is the Developmental explanation for the Precambrian explosion?
It suggests that the oxygen levels were high but the genetics were not there for organisms to evolve until a while later
What were the Ecological explanations for the precambrian explosion?
- Simply a mass extinction where everything got wiped out and we started over with a new set of organisms
- Evolution of eyes that caused prey to find new ways to survive ie. growing a shell
- Development of zooplankton that ate plankton making poo organic carbon at the bottom of the ocean
What is a Lagerstatten?
A fossil site that has a community rather than individual fossils
What is the significance of the Burgess Shale?
It is essentially a community growing on a landslide with entire communities left intact. It is the most important geological site for paleontologists in the world
What is the relative amount of organisms in the Cambrian?
The Cambrian is dominated by many organisms while the precambrian is dominated by a little bit of organisms
What is the order of evolution?
Fish ➡️ amphibians ➡️ reptiles ➡️ mammals
How did Fish evolve into Amphibians?
They evolved arms and started to take in oxygen through the air
What is required for amphibians to reproduce?
Returning to water
How do reptiles evolve form amphibians?
They grow on land and don’t need to return to the water to reproduce
What did plants look like during the precambrian?
Just bacterial biofilms and algae growing on rocks and stuff
What was the very first plant?
Fern
What are most of the major coal deposits made of?
The remnants of fern
What are Gymnosperms?
Non-flowering plants
What plants evolve after Fern?
The Gymnosperms and the angiosperms
What are angiosperms?
Plants with both seeds and flowers
What is the evolution of plants?
Going from bacteria and algae to fern to gymnosperms and angiosperms
What is a Mass Exinction?
A large portion in earth’s history where a lot of things were wiped out
What were the two major mass extinctions?
- Permian-Triassic
* Cretaceous-Tertiary
Why do we only talk about mass extinctions as a phanerozoic phenomenon?
Because we can’t tell if previous mass extinctions occurred because microbes can’t mineralize
What are the two main things that contribute to mass extinctions?
Environmental and Extraterrestrial
What died during the Permian Extinction?
90% of all marine species and 70% of animals on land
What happened during the Permian extinction?
A large igneous province occurred releasing a bunch of gasses (CO2 and SO2) forming carbonic and sulfuric acid and acid rain and the ash blocked out sunlight killing all the organisms. Acid rain increased chemical weathering and more nutrients get washed in the ocean and plankton blooms using all the oxygen and the ocean becomes anoxic
What happened in the Cretaceous extinction?
A meteor came and killed all the dinosaurs blocked out all the sunlight
What is proof of the Cretaceous exctintion?
The layer of ash and also finding iridium in the earth
What is the significance of Flood Basalts in India?
There was a volcano that occured at the same time that could be responsible for the cretaceous extinction
