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

C-Origin and Early Evolution of Life Flashcards

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Biology 101 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
Q

Steps to life

A

Compounds and protocells - small and medium sized molecules - large molecules
——threshold——–
Prokaryotes (cells) - eukaryotes (cells) - multicellular organisms (cells)

26
Q

What does the Miller-Urey synthesis of amino acids show? What was it and what did it relate to?

A

Change of compounds to molecules

An experimental study related to the atmosphere (mainly secondary)

27
Q

What is the composition of the atmosphere according to the Miller-Urey synthesis of amino acids?

A

Methane (CH4)
Ammonia (NH3)
Hydrogen (H2)
Water vapour (H2O)

28
Q

What were the results of the Miller-Urey synthesis of amino acids? (5)

A

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
Q

What was dissolved in water for the Miller-Urey synthesis of amino acids?

A

Amino acids

30
Q

What is the essential thing to know about the Miller-Urey synthesis of amino acids?

A

Easy to synthesise amino acids in more reducing atmosphere (earlier Earth life)
More difficult in less reducing

31
Q

Is it possible to have pockets of more reducing atmosphere locally?

A

Yes from volcanic activity and lightening (environmental conditions and energy)

32
Q

What experiment shows the change of molecules into cells? (formation of cells)

A

Fox’s Protenoid Microspheres

33
Q

What is the result of Fox’s Protenoid Microspheres?

A

Protein like microspheres formed abiotically from amino acids (combining glumatic and aspartic acids)

34
Q

What occurred in Fox’s Protenoid Microspheres?

A

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
Q

What contexts does Fox’s Protenoid Microspheres occur?

A 
Hydrothermal systems (strong temperature gradients, Shorefaces (tidal), Geothermal fields in terrestrial settings
ie. hostile environments may have promoted cell replication
36
Q

What is the model for the evolution of prokaryotes into eukaryotes?

A

Endosymbiosis (Endosymbiotic theory of cell evolution)

37
Q

What evidence is there of an extra-terrestrial source of organic molecules?

A

Murchison Meteorite
Amino acids
Not terrestrial contamination
Indicates synthesis of amino acids can occur elsewhere in Solar System

38
Q

What is Panspermia?

A

The idea that life evolved elsewhere and ‘seeded’ earth

39
Q

What ‘proof’ is there of Panspermia?

A

Allan Hills, Antarctica - Martian meteorite with possible evidence of bacteria

40
Q

Chemical evidence of life - 4100 Ma

a) Location, b) Data, c) Evidence

A

a) Jacks Hills Australia
b) Carbon Isotopes
c) Strongly negative σ13C values for graphite in zircon (rocks recycled as grains into younger rocks)

41
Q

Chemical evidence of life - 3850 Ma

a) Location, b) Data, c) Evidence

A

a) Akilia Island, Greenland
b) Carbon Isotopes
c) Strongly negative σ13C values for carbonaceous inclusions in apatite

42
Q

Chemical evidence of life - 3770 Ma

a) Location, b) Data, c) Evidence

A

a) Isua, Greenland
b) Carbon Isotopes
c) Strongly negative σ13C values for carbonaceous inclusions in apatite

43
Q

Fossil Evidence of life - 3500 Ma

a) Location, b) Data, c) Evidence

A

a) Apex Chert, Australia
b) Body Fossils
c) Controversial - originally interpreted as marine fossils (and cyanobacteria), many reinterpretations, still fossils

44
Q

Fossil Evidence of life - 3235 Ma

a) Location, b) Data, c) Evidence

A

a) Pilbara, Australia
b) Body Fossils
c) Filamentous microfossils in hydrothermal setting - land based stromatolites (implications of where life evolved?)

45
Q

What is the difference between C12 and C13?

A

C12 has 6 neutrons, C13 has 7

46
Q

Which is lighter, C12 or 13?

A

C12

47
Q

Which C do biological processes favour?

A

C12

48
Q

What are isotopes?

A

Different types of atoms of the same chemical element , same atomic number but different mass number (variation in neutrons)

49
Q

What are stable isotopes?

A

Isotopes that don’t undergo radioactive decay

50
Q

Stable Isotope Analysis (4)

A

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
Q

Stable Isotope Analysis - Jacks Hills Australia (3)

A

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
Q

Stable Isotope Analysis - Akilia Island, Greenland (3)

A

Carbonaceous inclusions in apatite
3850 Ma
δ13C = -37%

53
Q

Stable Isotope Analysis - Isua, Greenland (3)

A

Carbonaceous inclusions in apatite
3770 Ma
δ13C = -30%

54
Q

Body Fossils - Apex Chert, Warrawoona Group, Pilbara, Australia (4)

A

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
Q

Can abiological processes produce artefacts that resemble microfossils?

A

Yes, through mineral precipitation (biomorphs)

Organic hydrocarbons condense onto filaments which signals ‘fossils’

56
Q

Argument to Apex Chert being of biological origin

A

Structures hollow with walls and transverse divisions not solid
Distinctive C isotope similar to today’s bateria

57
Q

Body Fossils - Pilbara, Australia (5)

A 
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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