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Intro to Earth Science > C-Origin and Early Evolution of Life > Flashcards

C-Origin and Early Evolution of Life Flashcards

1
Q

What does LUCA stand for?

A

Last Universal Common Ancestor

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2
Q

What does all life share?

A

One LUCA

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3
Q

What evidence favours the notion of a single origin/LUCA? (4)

A

Only 4 nucleotide bases used in genetic material (in DNA+RNA)
DNA + RNA are bases of heredity (DNA=genetic instructions, RNA=coding and expression)
Only 20 L-amino acids used in proteins
ATP is energy currency for all organsims (to ADP=energy for processes in living cells)

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4
Q

What is a nucleotide?

A

Organic molecules that are sub-units of nucleic acids bases-compounds inside these

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5
Q

What does DNA stand for?

A

Deoxyribonucleic acid

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6
Q

What does RNA stand for?

A

Ribonucleic acid

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7
Q

What are amino acids?

A

Simple organic compounds (building blocks of life)

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8
Q

What are the properties for the living state?

A

Self-replication
Metabolism
Containment
Sensory Function

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9
Q

What does self-replication involve?

A

Nucleic Acids - DNA & RNA

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10
Q

What is metabolism?

A

The chemical processes that occur within a living organism in order to maintain life
(anaerobic and aerobic organisms)

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11
Q

What does containment involve?

A

Membranes and cell walls

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12
Q

What are membranes?

A

Outermost layers in animal cells; present in plant cells which also have a cell wall (robust); bacteria have membranes and cell walls

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13
Q

What is containment?

A

Cells are contained by outermost membrane, but can also ‘sense’ outer environment

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14
Q

What are the 3 properties/functions of membranes?

A

1) Separation from medium
2) concentrate biomolecules
3) allow preservable variations

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15
Q

What is the function of channel protein?

A

Allows transport of specific substances across a cell membrane

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16
Q

What is the function of receptor proteins?

A

Receive chemical signals from outside a cell

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17
Q

What are a) phospholipids and b) fatty acid tails?

A

a) hydrophylic

b) hydrophobic

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18
Q

What is the potential of properties of membranes and cell walls in the fossil record?

A

Gunflint Chert, Lake Superior (Ontario/Minnesota)
1.8Ga
Hollow cell content not fossilised - permineralisation

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19
Q

What does the sensory function involve?

A

The nervous system

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20
Q

What are the principal chemical constituents for life?

A

H, O, C, N, P, S

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21
Q

What are proteins?

A

Important components of every cell and building blocks of bone, cartilage, skin etc

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22
Q

What is abiogenesis?

A

The original evolution of life from inorganic/inanimate substances

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23
Q

What is the pathway to life?

A

Elements - Compounds - Molecules (threshold - when it becomes life after this) - Cells - Tissues - Organs

24
Q

What is the threshold in relation to this?

A

When inorganic matter became life

25
Steps to life
Compounds and protocells - small and medium sized molecules - large molecules ------threshold-------- Prokaryotes (cells) - eukaryotes (cells) - multicellular organisms (cells)
26
What does the Miller-Urey synthesis of amino acids show? What was it and what did it relate to?
Change of compounds to molecules | An experimental study related to the atmosphere (mainly secondary)
27
What is the composition of the atmosphere according to the Miller-Urey synthesis of amino acids?
Methane (CH4) Ammonia (NH3) Hydrogen (H2) Water vapour (H2O)
28
What were the results of the Miller-Urey synthesis of amino acids? (5)
24 different amino acids Sensitive to starting conditions Secondary atmosphere=less reducing variety *Easy to synthesise amino acids in more reducing atmosphere (early in Earth life)* More difficult to do so in less reducing atmosphere
29
What was dissolved in water for the Miller-Urey synthesis of amino acids?
Amino acids
30
What is the essential thing to know about the Miller-Urey synthesis of amino acids?
Easy to synthesise amino acids in more reducing atmosphere (earlier Earth life) More difficult in less reducing
31
Is it possible to have pockets of more reducing atmosphere locally?
Yes from volcanic activity and lightening (environmental conditions and energy)
32
What experiment shows the change of molecules into cells? (formation of cells)
Fox's Protenoid Microspheres
33
What is the result of Fox's Protenoid Microspheres?
Protein like microspheres formed abiotically from amino acids (combining glumatic and aspartic acids)
34
What occurred in Fox's Protenoid Microspheres?
Solutions of amino acids subjected to heating-cooling cycles Dehyration-rehydration cycles Suggestive of splitting (replication) Relevance to origin of life now thought to be limited (cells walls of bacteria are lipids not proteins)
35
What contexts does Fox's Protenoid Microspheres occur?
``` Hydrothermal systems (strong temperature gradients, Shorefaces (tidal), Geothermal fields in terrestrial settings ie. hostile environments may have promoted cell replication ```
36
What is the model for the evolution of prokaryotes into eukaryotes?
Endosymbiosis (Endosymbiotic theory of cell evolution)
37
What evidence is there of an extra-terrestrial source of organic molecules?
Murchison Meteorite Amino acids Not terrestrial contamination Indicates synthesis of amino acids can occur elsewhere in Solar System
38
What is Panspermia?
The idea that life evolved elsewhere and 'seeded' earth
39
What 'proof' is there of Panspermia?
Allan Hills, Antarctica - Martian meteorite with possible evidence of bacteria
40
Chemical evidence of life - 4100 Ma | a) Location, b) Data, c) Evidence
a) Jacks Hills Australia b) Carbon Isotopes c) Strongly negative σ13C values for graphite in zircon (rocks recycled as grains into younger rocks)
41
Chemical evidence of life - 3850 Ma | a) Location, b) Data, c) Evidence
a) Akilia Island, Greenland b) Carbon Isotopes c) Strongly negative σ13C values for carbonaceous inclusions in apatite
42
Chemical evidence of life - 3770 Ma | a) Location, b) Data, c) Evidence
a) Isua, Greenland b) Carbon Isotopes c) Strongly negative σ13C values for carbonaceous inclusions in apatite
43
Fossil Evidence of life - 3500 Ma | a) Location, b) Data, c) Evidence
a) Apex Chert, Australia b) Body Fossils c) Controversial - originally interpreted as marine fossils (and cyanobacteria), many reinterpretations, still fossils
44
Fossil Evidence of life - 3235 Ma | a) Location, b) Data, c) Evidence
a) Pilbara, Australia b) Body Fossils c) Filamentous microfossils in hydrothermal setting - land based stromatolites (implications of where life evolved?)
45
What is the difference between C12 and C13?
C12 has 6 neutrons, C13 has 7
46
Which is lighter, C12 or 13?
C12
47
Which C do biological processes favour?
C12
48
What are isotopes?
Different types of atoms of the same chemical element , same atomic number but different mass number (variation in neutrons)
49
What are stable isotopes?
Isotopes that don't undergo radioactive decay
50
Stable Isotope Analysis (4)
Ratio of two isotopes uses δ notation Abiological and biological processes use isotopes differently Biological use lighter isotopes - gives different value for δ As result of these processes, carbon has different C13:C12 ratio
51
Stable Isotope Analysis - Jacks Hills Australia (3)
C12/C13 of graphite (carbon) in 4.1Ga zircon Graphite encased in crack-free zircon - no contamination from recent geological processes δ13C of −24 ± 5% - consistent with biogenic origin (terrestrial biosphere by 4.1Ga?)
52
Stable Isotope Analysis - Akilia Island, Greenland (3)
Carbonaceous inclusions in apatite 3850 Ma δ13C = -37%
53
Stable Isotope Analysis - Isua, Greenland (3)
Carbonaceous inclusions in apatite 3770 Ma δ13C = -30%
54
Body Fossils - Apex Chert, Warrawoona Group, Pilbara, Australia (4)
3500 Ma Originally interpreted as body fossils via permineralisation Earliest marine fossils Within marine deposits - chert and basalts Included candidate cyanobacteria (Oscillatoria) - oxygenic photosynthesis? Revisited and interpreted as abiogenic and artefacts
55
Can abiological processes produce artefacts that resemble microfossils?
Yes, through mineral precipitation (biomorphs) | Organic hydrocarbons condense onto filaments which signals 'fossils'
56
Argument to Apex Chert being of biological origin
Structures hollow with walls and transverse divisions not solid Distinctive C isotope similar to today's bateria
57
Body Fossils - Pilbara, Australia (5)
``` 3235 Ma - earliest land fossils Microscopic filaments Volcanogenic massive sulphides Land hydrothermal setting Hot Springs and stromatolites ```

Intro to Earth Science (13 decks)

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