Lecture 25

Question 1

The first cells needed to create

Answer 1

1. proteins as a catalyst for energy production
2. nucleic acid for replication and transfer of its genetic properties
3. carbohydrates as the structural backbone of the cell wall
4. lipids as seld-sealing cell envelopes that protected the cytoplasmic contents from becoming randomly dispersed

Question 2

What did prebiotic earth look like

Answer 2

There was a 1500 degree temperature with no solid rocks - formed by the collision of earth and Theia

Question 3

Earth’s differentiation

Answer 3

After accretion, the earth’s internal temperatures melted all elements. Once liquified, magnetic materials become more mobile and sink via gravity to the core while lighter materials such as silicates float outwards from the center to form mantle and crust.

Question 4

Komatiite

Answer 4

Rocks that were basaltic and rich in magnesium and nickel. They were the first rocks to form on earth - making up low-lying volcanic islands.

Question 5

Waterworld

Answer 5

Earth was initially completely submerged with few volcanic islands

Question 6

Oldest rock on earth

Answer 6

4 Gyr Acasta Gniess from NWT and Jack hills belt in Western Australia used to radiometric dating of zircons (a mineral that lasts a long time)

Question 7

Oldest sedimentary rock

Answer 7

3.85 Ga Isua greenstone complex in Greenland

Question 8

Old earth environment

Answer 8

• Low luminosity from the sun
• High CO2 keeps the earth warm
• low free oxygen leading to no ozone absorbing radiation
• acid rain (atmosphere rich in carbonic acid, sulfuric acid, and hydrochloric acid)

Question 9

Panspermia

Answer 9

microbial hitchhikers on meteorites (guess that life arrived here from somewhere else on a meteorite)

Question 10

Guesses of how life formed

Answer 10

1. Organic soup model: Key prebiotic monomers (CH2O and HCN) were formed when reduced gases in the atmosphere were subjected to UV irradiation and ane electrical discharges. They condensed to form more complex compounds such as amino acids that accumulated into seawater
2. Meteorites passed through the atmosphere causing shock waves that formed CH2O or HCN and ionized the reduced atmospheric gases
3. Panspermia

Question 11

Problems with guesses of how life formed

Answer 11

Monomers would have had difficulty forming in the deep ocean due to monomer dispersion, large quantities of CO2 in the atmosphere would not be as reduced as proposed, methane did not exist before life evolved

Question 12

The experiment of synthesizing amino acids

Answer 12

Urey-Miller experiment

Question 13

Hydrothermal model

Answer 13

Life arose in sheltered environments with sites of bioessential nutrients, namely, the diffuse vents and black smokers associated with mid-ocean ridge systems may have offered the most favourable conditions for early life.

Question 14

The major issue with the organic soup model

Answer 14

Giant impacts would have constrained the timing of the earth’s origin at the surface - as post-impact plumes of vaporized rock would have enveloped the entire planet and evaporated the upper water column. This increased surface pressure to above 100 bars and raised temperatures high enough to sterilize much of the planet for several thousands of years.

Question 15

All organisms with the same last common ancestor have the following in common:

Answer 15

love hot water

Question 16

The earliest cells may have been used for early respiration:

Answer 16

sulfur (sulfur oxidation) and methane (methane genesis) (H2S and CH4)

Question 17

The three Eons

Answer 17

Haden (4560-4000 million ya), archaean, and proterozoic

Question 18

Biomarkers for organic life

Answer 18

Microfossils, biogenic structures (stromatolites), isotopes, and biomarkers

Question 19

Stromatolites

Answer 19

Recognized as the oldest visable signs of life on Earth. They have cross-sectional layers and complex internal features.

Question 20

The oldest stromatolites are located in:

Answer 20

3.42 billion year old “egg carton” stromatolites from North Pole in the Pilbara region, Western Australia.

Question 21

MISS (microbially induced sedimentary structures)

Answer 21

one of the oldest forms of fossil evidence, having been characterized in rocks as old as 3.2 Ga in age and are formed by microbial mats of filamentous bacteria trapping siliciclastic sediments in more energetic tidal flat settings

Question 22

Biomarkers

Answer 22

the organic compounds derived from more complex precursors to provide information about their relative abundance in ancient environments

Question 23

When doing research, it is important not to confuse contamination for _____

Answer 23

biomarkers

Question 24

The most important biological innovation was the ________ by the for-runners of modern ____.

Answer 24

evolution of oxygenic photosynthesis

cyanobacteria

Question 25

The most important reaction done by ancient cyanobacteria

Answer 25

CO2 +H2O –> CH2O + O2

Question 26

When did the great oxidation event occur

Answer 26

2.5 billion years ago

Question 27

The great oxidation event

Answer 27

the first time oxygen accumulated in the atmosphere was due to bacteria producing oxygen