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Genetics and evolution > Origins of Life > Flashcards

Origins of Life Flashcards

1
Q

Describe Earth during the Hadean time period.

A 
Earth spinning rapidly
Smoggy toxic environment 
Dust/ ash in atmosphere
Anaerobic
Surface mostly water
Violent 30m+ tides
Acidic sea, boiling and churning 
Some landed peaks above sea
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2
Q

What are the 7 basic chemical characteristics of life on Earth?

A
  1. Carbon based
  2. Use energy
  3. Use oxidative gradients
  4. Contain proteins, lipids and carbs
  5. Use nucleic acids for heredity
  6. Use ATP
  7. Same basic metabolic reactions
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3
Q

Where do membranes originate from?

A

Froth of iron sulphide bubbles around alkaline vents, simple organic molecules formed through catalysis of iron-nickel sulphides. Diffused from sources and collided, eventually accumulating and coating inside surface of bubbles with more robust protein synthesis

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4
Q

How many divergences were there post- LUCA?

A

2

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5
Q

When did Eukarya split off?

A

1.8bya

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6
Q

Describe what the oceans on Venus and Mars are like, to our knowledge.

A

Can’t tell for Venus, no way to survey

Mars= barren and dry

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7
Q

Why are there no oceans on Venus or Mars?

A

No ozone layer so UV splits water and the H2 is lost to space as it isn’t very dense and the O2 gets incorporated

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8
Q

Why did Earth have a massive increase in oxygen?

A

Due to the emergence of photosynthetic life

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9
Q

What was the Great Oxygenation Event? (come on, you have to get this right. It is legit in the name)

A

Massive increase in O2 levels on Earth

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10
Q

What were the causes of the Great Oxygenation Event?

A

Late appearance of the oxygen producing life forms
Reduction in reactive gases
Oxygen from photosynthesis

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11
Q

What were some possible impacts of increased oxygen levels?

A

Extinction of anaerobes?

Ice age 2.45-2.2 bya

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12
Q

What are the benefits of photosynthesis for an organism?

A

Free carbon source

Free living and protection

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13
Q

What is needed for photosynthesis?

A

Reducing power
Energy
Catalyst
Precursor to add carbon dioxide to

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14
Q

What would primitive photosynthesis have? e.g. What do all photosynthetic organisms have in common?

A 
Photosystem
Pigments
RuBISCO
Manganese cluster
ATP
Synthase, or equivalent
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15
Q

What does photosystem I do?

A

Uses light energy to drive the production of a strong reducing agent

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16
Q

What does photosystem II do?

A

Uses light energy to drive the import of protons to make a redox gradient to drive ATP production

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17
Q

What are the two common features of all electron transport methods?

A

Absorb light

Allow for protons to move

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18
Q

Why is there variation in certain common structures?

A

Selective loss: structures removed by mutation or deletion

Selective fusion: structures combined by duplication/ rearrangement

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19
Q

Why did photosystems probably evolve?

A

As an independent proton gradient

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20
Q

What are the two semi-autonomous organelles?

A

Mitochondria and chloroplasts

21
Q

What are the defining features of semi-autonomous organelles?

A

Specific, distinct metabolic functions and structures
Circular DNA genomes with unique organelle genes
Transcription/ translation machinery
Distinct biogenesis with specific pathway, regulated by the cell
Self replicating by binary fission

22
Q

What is the Endosymbiosis theory?

A

Has been argued semi-autonomous organelles were originally independent prokaryotes that got engulfed by a primitive eukaryote and incorporated into the cell

23
Q

What is the shopping bag model?

A

The contents of a shopping bag don’t all have to come from the same shop
There may have been multiple endosymbiosis events with each one transferring more info

24
Q

What is the circumstantial evidence for the endosymbiosis theory?

A 
Approximate size
No. of membranes 
Circular genome
Prokaryotic enzymes and complexes
Prokaryotic codon usage 
Examples of multiple endosymbioses
25
Q

What is the molecular evidence for the endosymbiosis theory?

A

Ox-Phos complexes similar in prokaryotes
Photosynthetic mechanisms in chloroplasts nearly identical to cyanobacteria
Nuclear genes affecting organelles same basically as in prokaryotes
Division proteins and mechanisms

26
Q

How old is the universe?

A

13.7 bya

27
Q

What happens first in the formation of the early solar system and when?

A

Explosion of a star 4.55bya
Formation of compounds, heavy metals, etc
Dust/ gas cloud begins to collapse “Nebula”
Gravity takes over
Rotation around fixed point

28
Q

What happens 1 million years after the early solar system begins to form?

A 
Dust cloud coalesces
Gravity takes over
Rotation around fixed point 
Spinning cloud flattens to disc
Particles collide
29
Q

What happens 2 million years after the early solar system begins to form?

A 
Planets form (planetessimals)
Inner plants form from mineral solids
Outer planets from gases
Protoplanets
Major collisions
Gas giants form
30
Q

What happens 50 million years after the early solar system begins to form?

A

The sun ignites
Inner planets still chaotic and small
Jupiter supports Asteroid belt

31
Q

What happens 75 million years after the early solar system begins to form?

A

Earth increases in size with the protoplanet companion (Thea)
Collision
Moon forms

32
Q

What did Late Heavy Bombardment do?

A

Sterilises Earth
Water falls to Earth
Meteorites fall

33
Q

Where did the initial water on Earth allegedly come from?

A

Comets from Late Heavy Bombardment
Minerals dissolved in water
Water covers planet
Has been disputed recently

34
Q

When did life roughly begin on Earth?

A

3.8bya

35
Q

What is the panspermia theory of the origin of life?

A

Living organisms seeded by meteorites
Meteorites identified from Mars
Contain mineral deposits
Possible fossils?

36
Q

What is the mineral clays theory of origin of life?

A

Water-bearing clays form concentration vessels for replication and patterning
Source of mineral salts for catalysis of early processes
Largely unsupported or supplanted

37
Q

What is the primordial soup theory of the origins of life?

A

Key elements react and form basic compounds for life
Amino acids
Nucleic acids
Carbon based
Spark of life from high energy source like lightning

38
Q

What did the Miller-Urey experiments intend to do?

A

Replicate conditions of Early Earth based on atmosphere of Jupiter

39
Q

What was the major problem with the Miller-Urey experiments?

A

Didn’t have the right composition of gases for what rock composition has shown early Earth probably had

40
Q

What is the issue with the primordial soup theory?

A

Unlikely to happen spontaneously
Lightning is just as likely to destroy as it is to create
Large planet wide ocean wild mean compounds would be dilute, making reaction more unlikely

41
Q

Describe alkali vents.

A 
Warm
Strongly alkaline (yeah, I know, duh)
Complex structures
Reduces components of seawater 
Releases energy as heat
42
Q

Is it more likely that DNA, RNA or protein came first?

A

RNA

43
Q

Why is it unlikely DNA existed before RNA or protein?

A

No known instances of DNA-catalysed protein activities

and DNA replication isn’t conserved

44
Q

Why is it more likely RNA evolved before DNA and protein?

A

RNA can act as a catalyst

45
Q

What is the likely origin of DNA?

A

DNA and RNA are very similar
Reasonable to suspect DNA evolved from RNA
More permanent, stable structure

46
Q

How do you synthesise carbon based compounds from scratch?

A

The TCA (Krebs) Cycle used backwards
With enough of the needed compounds, the cycle will run on its own
Needs ATP

47
Q

LUCA was not free-living. What did it rely on? Why was it not free living?

A 
In vent, mineral cells
Mineral cells could provide:
concentration
stable environment 
redox potential 
catalysts
concentrations of nucleic acids
sub-structure for chemical reactants
48
Q

What was needed to exist outside of mineral cells?

A

Membrane

Genetics and evolution (10 decks)

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