Origin of Life

Question 1

When was earth created

Answer 1

4.6 billion years ago

Question 2

When did life being

Answer 2

3.5 billion years ago

Question 3

Pre-Cambrian period

Answer 3

-makes up 90% of Geological Time Scale
- made up of Hadean, Archeon, and Proterozoic eons

Question 4

Order Eons chronologically

Answer 4

Hadeon (4.6-4bya) - Archeon (4-2.5 bya) - Proterozoic (2.5-541 mya)

Question 5

Hadean Eon

Answer 5

-time before a reliable (fossil) record of life
- temps are extremely hot
- no oxygen
- ejected debris following giant impact collision between early earth and an ancient planet called theia is thought to have formed the moon

Question 6

Archeon Eon

Answer 6

• volcanic activity was considerably higher than today, with numerous lava eruptions
• without oxygen
• beginning of life on earth and evidence of cyanobacteria
• life was limited to simple-celled organisms lacking nuclei (prokaryotes)
• earths crust had cooled to allow formation of continents
• earliest identifiable fossils (stromatolites)

Question 7

Proterozoic Eon

Answer 7

• appearance of oxygen to just before the proliferation of complex life (such as corals)
• bacteria began producing oxygen, leading to the sudden rise of life forms
• eukaryotes cells emerge, including some forms of soft-bodied multicellular organisms

Question 8

Describe how stromatolites formed

Answer 8

• form in shallow water
• column shaped structures made up of layers of sedimentary rock, created by mats of cyanobacteria living on top of stromatolite
• cyanobacteria continue to reproduce on upper surface of mats as these cells depend on light for photosynthesis
• sediments begin to settle and accumulate on top of cyanobacteria, block sunlight, cyanobacteria slowly move to top of this sediment layer, trapped sediment within stromatolite will harden into rock
• tiny living things, like bacteria and algae, grew together in layers on the bottom of shallow water

Question 9

Describe how banded iron formations are created

Answer 9

• consists of layers of iron oxides (either magnetite or hematite) separated by layers of chert, jasper or quartz
• each layer is usually narrow
• rock has a distinctively banded appearance because of differently colored lighter (chert, jasper, quartz) and darker iron-rich layers
• iron and oxygen in seawater combine to form iron oxide, which settles to the ocean floor as layers of sediment.

Question 10

Describe how red beds are formed

Answer 10

• huge deposits of iron-rich sediment
• once in air, 02 could react with iron in sediments on the earths surface, which produced rust-colored sedimentary rock known as red beds
• first appeared in geologic records 2 bya

Question 11

Explain how stromatolites, banded iron formations, and red beds are geological evidence of free oxygen on early earth during Pre-Cambrian period

Answer 11

-stromatolites needed oxygen to survive, their presence suggests oxygen was available in the environment
-iron formations created when iron in seawater combined with oxygen
-red beds are rock with a reddish color due to the presence of iron oxide, which forms when iron reacts with oxygen

Question 12

Explain how stromatolites led to the existence of banded iron formations and red beds

Answer 12

-stromatolites were formed by tiny living organisms, like bacteria and algae, which released oxygen during their life processes
-oxygen combined with iron in the seawater, forming banded iron formations as layers of iron-rich rocks settled on the ocean floor
-oxygen continued to build up in the atmosphere, it reacted with iron in the land, leading to the formation of red beds with iron oxide-rich rocks.

Question 13

Phanerozoic Eon

Answer 13

• represents the period of earths history with advanced life forms
• Paleozoic, Mesozoic, and Cenozoic eras

Question 14

Paleozoic Era

Answer 14

-542 to 251 million years ago
- longest period of Phanerozoic Eon
- composition of air was very similar to current atmosphere (80% nitrogen and 20% oxygen)
- formation of Pangaea
- Cambrian explosion

Question 15

Cambrian Explosion

Answer 15

535 to 525 million years ago
- most intense burst of evolution ever know
-earliest fossil appearance of many major groups of living animals

Question 16

List and explain 6 reasons that triggered the Cambrian explosion

Answer 16

1. Higher oxygen levels in atmosphere
   - made aerobic respiration more efficient over anaerobic respiration and fermentation
2. Evolution of predation
   - predation exerted selection for defensive structures, body plans for rapid movement
3. New ecological niches
   - evidence of animals burrowing under, living on, and swimming above sea floor
4. New developmental genes
   - early animals had few or no hox genes
5. Snowball earth hypothesis
   - planet was covered with thick sheet of ice, last thawing triggered diversification by releasing nutrients into oceans
6. Ozone formation
   -marine organisms became mobile and were able to live in shallower areas of ocean with more sunlight exposer

Question 17

Identify when animals first appeared in the Geological Time Scale

Answer 17

• Proterozoic era of Precambrian period
  -635-541 mya

Question 18

Adaptive radiation
exmaples

Answer 18

• rapid production of many descendant species (with wide range or forms) from a single lineage
  ex. cambrian explosion, darwins finches, diversification of mammals following extinction of dinosaurs, australian marsupials

Question 19

List 3 hallmarks for adaptive radiation

Answer 19

-monophyletic group
- rapid speciation
- ecological diversification into many niches: niche describes range of resources that a species can use and range of conditions that it can tolerate

Question 20

Mesozoic Era

Answer 20

• 251 to 65.5 million years ago
• break up of Pangaea
• Coral reefs emerged
• Dinosaurs were dominant terrestrial vertebrates
• known as the “Age of Reptiles”
• Gymnosperms were dominant terrestrial plants
• first mammals emerged (were tiny nocturnal insect-eaters)
• warm period during this time that there was no ice caps

Question 21

Cenozoic Era

Answer 21

• 65.5 million years ago to now
• mammals were dominant terrestrial vertebrates
• know as the “Age of Mammals”
• angiosperms are most dominant terrestrial plants
• global climate gradually cooled through this time