Lecture test 1: Key events in earth's history

Question 1

Order of key events

Answer 1

1. Pharenerozoic eon covers when life started on earth
2. Oxygen revolution
3. First eukaryotes
4. Origin of multicellular organisms
5. Colonization of land and tetrapods
6. Mass extinctions

Question 2

1. Pharenerozoic eon covers when life started on earth

Answer 2

• Divided into 3 eras: Paleozoic, Mesozoic, Cenozoic
• Includes last 1/2 billion years
• First single celled organisms developed (prokaryotes)
• Oldest known fossil is stromatolites

Question 3

2. Oxygen revolution

Answer 3

• Most atomospheric oxygen is of biological origin
• Produced through photosynthesis
• Caused extinction of many prokaryotic groups

Question 4

3. First eukaryotes

Answer 4

• Have a nucelar envelope, mitochondria, ER, and cytoskeleton
• Endosymbiont theory: mitochondria and plastids were formally small prokaryotes (cell living within host cell)

Question 5

4. Origin of multicellular organisms

Answer 5

• Gave rise to plants, animals, fungi, algae
• Cambrian explosion: sudden appearance of fossils resembling modern animals
• Cambrian explosion provides first evidence of predator prey interactions

Question 6

5. Colonization of land

Answer 6

• Began to colonize 500 mya
• Tetrapods evolved from lobe-finned fishes
• Humans began to evolve from them

Question 7

6. Mass extinctions

Answer 7

• Considered mass extinction if 50% or more species on earth go extinct
• Can be caused by changes to a species environment
• “Big 5” mass extinction events
• Permian and cretaceous extinctions
• Consequences of mass extinctions: takes millions of years for diversity to recover. Change types of organisms found in ecological communities (EX: percentage of marine predators increased after permian and cretaceous exinctions)