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BIO239 Microbiology And The Cycles Of Life > L1 Origins Of Life > Flashcards

L1 Origins Of Life Flashcards

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Biology 101 flashcards
1
Q

What are the 6 essential elements

A

Carbon, hydrogen, oxygen, nitrogen, sulphur and phosphorus

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2
Q

What are 3 fundamental conditions for life on earth

A

Essential elements,
Continual source of energy,
Temperature allowing liquid water to

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3
Q

What are two continual sources of energy

A

Solar or geothermal

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4
Q

What are the conditions where no life would exist

A

150C and 1atm

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5
Q

When was the earth formed

A

4.5 billion years ago

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6
Q

At what period was the earth formed

A

Hadean eon

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7
Q

How were the elements up to iron formed

A

Sun released hydrogen
Heating hydrogen formed helium and other elements up to iron

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8
Q

How were elements greater than iron formed

A

Supernova

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9
Q

What geological events bring new elements to an environment

A

Meteor strikes

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10
Q

What are the charges of the crust and core

A

Crust highly oxidised, core very reduced

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11
Q

What is the earths core made of

A

Iron

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12
Q

What is the crust made of

A

Silicon dioxide
Also carbonates and nitrates

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13
Q

Could life have existed before it evolved to what is is today? And how?

A

Life could have existed and been destroyed by repeated meteor bombardment and then only exist in deep rock

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14
Q

What was the early atmosphere made up of

A

Most carbon dioxide, similar to Mars

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15
Q

What would have happened if carbon dioxide had been continued to be released by all life

A

Earth would of continued to warm and life could not of existed

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16
Q

The atmosphere absorbs light and converts it to…

A

Heat

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17
Q

Example of a planet where there is too much carbon dioxide

A

Venus

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18
Q

Example of a planet where there is too little carbon dioxide

A

Mars

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19
Q

What could have early microbial action caused

A

The ice age

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20
Q

What may have reversed the ice age

A

Evolution of methanogens

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21
Q

What is light driven carbon dioxide fixation

A

Photosynthesis

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22
Q

When did photosynthesis evolve

A

At leat 3.4 billion years ago

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23
Q

What was the trend when the atmosphere was oxygenated

A

Would’ve fluctuated with a general upwards trend

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24
Q

Why did oxygen conditions fluctuate

A

It was too toxic to most life at the time

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25
Q

Why can earth be referred to as a closed biosphere

A

Everything currently here is what can be used, nothing more

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26
Q

How are products linked by metabolism between living organisms

A

Products from one type of metabolism are linked to other biological processes
Products released by one are used by another - food, biomass etc

27
Q

How long ago did life evolve

A

3.8 million years

28
Q

What is the name of the time period where life evolved

A

Achaean eon

29
Q

How was life able to develop

A

As stable oceans formed

30
Q

Why is water so important for life

A

Remains liquid over wide temperature range
Is a universal solvent
Allows membranes to form

31
Q

What are 4 evidences for the evolution of life 3.8MYA

A

Fossils
Isotopes ratios
Biosignatures
Oxidation state

32
Q

What two things can be used as fossils

A

Stromatolites and microfossils

33
Q

Where are stromatolites found today

A

Shark Bay, Australia

34
Q

What condition of Shark Bay allows stromatolites to survive and why

A

High saline pools = no predation

35
Q

How is the structure of stromatolites formed

A

Mucilage traps calcium carbonate, cementing biofilm and creating structure
Sediment-trapped mucilage forms rocks over time

36
Q

From how long ago do stromatolites show evidence of life

A

3.4BYA - Archaean period

37
Q

How do stromatolites fail to show evidence of life

A

Cannot see cells in fossils

38
Q

How far back can microfossils be dated

A

2 BYA

39
Q

What makes fossils form

A

Minerals precipitate

40
Q

What are the advantages of using microfossils

A

Cell forms are visible and measurable

41
Q

What else could have formed microfossils

A

Abiotic factors

42
Q

Why do microfossils not appear before 2 BYA

A

Archaean rock was not compatible as it is metamorphic which is modified by temperature and pressure which destroys the fossils
Only sedimentary rock forms these kinds of fossils

43
Q

Give an example of enzymes selecting isotopes

A

Carbon dioxide fixing RubisCo prefers carbon-12 over carbon-13

44
Q

What happens to the carbon in cells

A

Converted to calcium carbonate

45
Q

How can the difference in C12 and C13 be measured

A

(C13 / C12 (of experimental rock) - C131 / C12 (of standard rock))
Divided by (C13 / C12 (standard rock))
All timesed by 1000

46
Q

What other element can be used to show enzymes selecting isotopes and how far does this date back

A

Sulphur 34 and 32
From 3.5 MYA

47
Q

Advantages of using isotope ratios

A

Highly reproducible, provide physical measure
Strong evidence for dating earliest life
Can be used to calibrate phylogenetic trees

48
Q

Disadvantages of using isotope ratios

A

Only tells us life existed, not what it looked like or what it did
Cannot guarantee they are not produced abiotically - can’t prove a negative

49
Q

What will the amount of C-13 be in a biological source

A

Depleted

50
Q

What would a minus value for the difference in carbon isotopes show

A

Minus value indicates a depletion of C-13 compared to C-12

51
Q

What type of ion is soluble

A

Crustal ferrous (Fe2+)

52
Q

What is an oxidised ferric ion
Is it soluble

A

Fe 3+
Insoluble

53
Q

How can iron ions show varying oxygen concentrations

A

Layers of Fe3+ in sedimentart rock show alternating oxic and anoxic conditions
Grey layers of silicon oxide and red layers of ferric oxides

54
Q

What are 3 possible sources of energy in early Archaean oceans

A

Oxidised forms of iron, nitrogen or sulphur interacting with hydrogen and driven by light reactions
Light-driven ion pumps creating gradients across memebranes
Metahnogenesis (2H2 + CO2 -> Ch4 + H2O)

55
Q

What are the 3 models proposed for crearting life from energy

A

Prebiotic soup
Metabolist model
RNA world model

56
Q

Who came up with the prebiotic soup model
What experiment was carried out

A

Oparin and Miller
Common compounds (hydrogen, water, methane) put under heat and pressure forms biomolecules like gylcine. Eventually develops proto-cells but this is large leap

57
Q

What is the assumption of Oparin and Millers simulation and is it true

A

No oxygen present
Some evidence oxygen was present and could’ve reacted with N, Fe, S in prescence of UV light

58
Q

What are arguments against Oparin and Millers experiment

A

Big leap from amino acids to functional proteins and cell formation
Elements may have been too dilute in ancient oceans - shallow coastal pools, or intertidal surfaces seem a more likely source for these reactions

59
Q

How was the early cell membrane formed
Which theory does this stem from

A

Micelle shaken to form a bilayer
Formed from amphipathic fatty acid glycerol esters
Metabolists model

60
Q

How was each amino acid formed
Which of the 3 theories does this stem from

A

From a component of the TCA cycle and 2 dinucleotides - went on to form basis of genetic code
Metabolists model

61
Q

What is the nutrient cycle in the metabolist model

A

Self-sustaining carbon dioxide based metabolism similar to citric acid (TCA) cycle which was catalysed by metal sulphides

62
Q

What does the RNA world model account for that is not covered in other models

A

The production of macromolecules that encode complex information

63
Q

Why is it RNA model and not DNA

A

RNA uses uracil which is produced earlier than thymine (DNA)

64
Q

How did adenine form in the RNA world model

A

From NH3 and carbon dioxide in ancient oceans

BIO239 Microbiology And The Cycles Of Life (12 decks)

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