Lecture 25: Archean Biosphere

Question 1

What did the first cells need to create?

Answer 1

• Proteins as catalysts for energy production
• Nucleic acids
• Carbohydrates as the structural backbone of the cell wall
• Lipids as self-sealing envelopes that protected the cytoplasmic contents from being randomly dispersed

Question 2

What did the early Earth form from?

Answer 2

A collision with a mars-sized planet (Theia) 4.5 billion years ago

Question 3

Why was the Hadean Earth very hot?

Answer 3

It was very hot (1500 Cº) from collision of particle and radioactive decay

Question 4

How long ago did the Hadean Earth form?

Answer 4

4.5 billion years ago

Question 5

Describe the crust of the Hadean Earth?

Answer 5

It was just magma no crust because of the heat

Question 6

How does differentiation occur after the Hadean Earth forms?

Answer 6

The earth shrinks due to gravitational compression and the internal temperature of earth increases causing iron and nickel to become the core and lighter silicates float upwards to form the crust

Question 7

What did the landmasses after the Hadean Earth mostly consist of?

Answer 7

Low-lying volcanic islands (similar to Hawaii)

Question 8

What were the earliest continents made out of?

Answer 8

Ultramafic rocks called Komatiites formed from peridotites

Question 9

What is the oldest rock on Earth?

Answer 9

The Acasta Gneiss found in the NWT

Question 10

What type of rock is the Acast Gneiss?

Answer 10

Metamorphic rock

Question 11

What is the only evidence of the earliest crust?

Answer 11

A few Zircons

Question 12

What does the presence of old sedimentary rock mean?

Answer 12

That there was some mechanism of transport i.e. water/ocean

Question 13

What kept the early Earth warm during the Archean period after the formation of continents?

Answer 13

High amounts of CO2 that heated the earth

Question 14

What was the rain like in early earth after the formation of continents?

Answer 14

Acid rain

Question 15

What is the Organic Soup theory of how organic compounds arose on earth?

Answer 15

Reduced gases in the atmosphere class (H2, CH4) were subjected to UV radiation and electricity and condensed to form amino acids in sea water without light needed

Question 16

Why couldn’t the Organic Soup and Meteroite model of how organic compounds arisen not work?

Answer 16

The atmosphere was not not reducing but instead filled with CO2 and methane cannot be formed inorganically and there is no hydrogen in the atmosphere

Question 17

What is the Extraterrestrial hypothesis for how organic compounds arose on earth?

Answer 17

Extraterrestrial meteorites falling to the earth could have brought organic compounds

Question 18

What is Panspermia?

Answer 18

The hypothesis that preformed life fell to earth bringing organic compounds

Question 19

Why couldn’t the Organic Soup, Meteorite, or Panspermia hypothesis be true?

Answer 19

Because they all would be occurring in open ocean and amino acids would be too dilute to join each other in the open ocean

Question 20

What is the solution to the Organic Soup, Meteorite, or Panspermia hypothesis?

Answer 20

A new method in which these processes occur in the open ocean with evaporation to concentrate it

Question 21

What is the Chemosynthesis hypothesis for how organic compounds emerged from the ocean?

Answer 21

Reduced gases emitted at hydrothermal vents reacted with oxidizing sea water to form HCN and CH2O and the mineral surfaces served as template for further polymerization reactions

Question 22

Why is the Hydrothermal Model more plausible?

Answer 22

Because they are sheltered from meteorites in the deep sea and there are many reducing nutrients from black smokers. They have energy sources, nutrients, and shelter and a solid surface for organic carbon to stick to on the vents

Question 23

Why is it hypothesized that life evolved in hot water?

Answer 23

Because the oldest organisms are thermophilic

Question 24

What source may the earliest cells have used as energy?

Answer 24

Sulfur or Methane oxidation

Question 25

What is the very beginning of Earth known as?

Answer 25

The Hadean Period

Question 26

What are the 3 periods of earth from oldest to youngest?

Answer 26

Hadean, Archean, Proterozoic

Question 27

What are the 4 evidences for Archean Life?

Answer 27

• Microfossils
• Biogenic structures
• Isotopes
• Biomarkers

Question 28

What are Microfossils formed from?

Answer 28

Fossilized bacteria

Question 29

How old are the oldest microfossils?

Answer 29

3.45 Ga

Question 30

What is the problem with Microfossils?

Answer 30

We can’t exactly tell what they are because we are only using looks to identify them

Question 31

What is the equation for Anoxygenic Photosynthesis?

Answer 31

H2 + 6CO2 ➡️ C6H12O6 + 6H2O

Question 32

What are Microbially Induced Sedimentary Structures?

Answer 32

One of the oldest forms of fossil evidence created by microbial mats of bacterial trapping sediments

Question 33

How do Isotopes tell us the age of an organism?

Answer 33

They give us the fraction of C12 and C13 which are characteristic of different life forms

Question 34

What are Biomarkers?

Answer 34

Organic compounds derived from more complex precursors to provide information on their relative abundance in ancient environments

Question 35

Which organism evolved to produce O2?

Answer 35

Cyanobacteria

Question 36

Why is Cyanobacteria significant and what is the reaction behind it?

Answer 36

They learned to split water to generate reducing power to fix CO2. CO2 + H2O ➡️ CH2O + O2

Question 37

When was the Great Oxidation event?

Answer 37

2.5 Billion years