Lecture 27: The Phanerozoic Biosphere

Question 1

What is the time span of the Phanerozoic era?

Answer 1

540 million years ago to now

Question 2

What is Significant about the Cambrian era?

Answer 2

It is characterized by rapid evolution and diverse life

Question 3

What is Cambrian Explosion?

Answer 3

The rapid explosion of life during the Cambrian era

Question 4

What are the three broad categories of things generally accepted to explain the cambrian explosion?

Answer 4

• Environmental
• Developmental
• Ecological

Question 5

What is the Environmental Explanation for the Precambrian Explosion?

Answer 5

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

Question 6

What is the Developmental explanation for the Precambrian explosion?

Answer 6

It suggests that the oxygen levels were high but the genetics were not there for organisms to evolve until a while later

Question 7

What were the Ecological explanations for the precambrian explosion?

Answer 7

• 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

Question 8

What is a Lagerstatten?

Answer 8

A fossil site that has a community rather than individual fossils

Question 9

What is the significance of the Burgess Shale?

Answer 9

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

Question 10

What is the relative amount of organisms in the Cambrian?

Answer 10

The Cambrian is dominated by many organisms while the precambrian is dominated by a little bit of organisms

Question 11

What is the order of evolution?

Answer 11

Fish ➡️ amphibians ➡️ reptiles ➡️ mammals

Question 12

How did Fish evolve into Amphibians?

Answer 12

They evolved arms and started to take in oxygen through the air

Question 13

What is required for amphibians to reproduce?

Answer 13

Returning to water

Question 14

How do reptiles evolve form amphibians?

Answer 14

They grow on land and don’t need to return to the water to reproduce

Question 15

What did plants look like during the precambrian?

Answer 15

Just bacterial biofilms and algae growing on rocks and stuff

Question 16

What was the very first plant?

Answer 16

Fern

Question 17

What are most of the major coal deposits made of?

Answer 17

The remnants of fern

Question 18

What are Gymnosperms?

Answer 18

Non-flowering plants

Question 19

What plants evolve after Fern?

Answer 19

The Gymnosperms and the angiosperms

Question 20

What are angiosperms?

Answer 20

Plants with both seeds and flowers

Question 21

What is the evolution of plants?

Answer 21

Going from bacteria and algae to fern to gymnosperms and angiosperms

Question 22

What is a Mass Exinction?

Answer 22

A large portion in earth’s history where a lot of things were wiped out

Question 23

What were the two major mass extinctions?

Answer 23

• Permian-Triassic

* Cretaceous-Tertiary

Question 24

Why do we only talk about mass extinctions as a phanerozoic phenomenon?

Answer 24

Because we can’t tell if previous mass extinctions occurred because microbes can’t mineralize

Question 25

What are the two main things that contribute to mass extinctions?

Answer 25

Environmental and Extraterrestrial

Question 26

What died during the Permian Extinction?

Answer 26

90% of all marine species and 70% of animals on land

Question 27

What happened during the Permian extinction?

Answer 27

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

Question 28

What happened in the Cretaceous extinction?

Answer 28

A meteor came and killed all the dinosaurs blocked out all the sunlight

Question 29

What is proof of the Cretaceous exctintion?

Answer 29

The layer of ash and also finding iridium in the earth

Question 30

What is the significance of Flood Basalts in India?

Answer 30

There was a volcano that occured at the same time that could be responsible for the cretaceous extinction