3. Early planet; early life Flashcards

1
Q

When did the Earth form?

A

4600Ma

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2
Q

When was the moon formed?

A

Approx 4500Ma

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3
Q

What is the period of 3900Ma to 3800Ma referred to as in Earth’s history? What does it mean for life on earth?

A

Late Heavy Bombardment
Earth’s surface was 100s of degrees hotter than amino acids/nucleotides can survive at - therefore life originated/re-originated after this point.

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4
Q

What is the approximate size of a prokaryotic cell?

A

0.1-10μm

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5
Q

What is the approximate size of a eukaryotic cell?

A

10-100μm

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6
Q

What are the key features of a prokaryotic cell?

A

No nucleus, organelles are not membrane-bound

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7
Q

Which evolved first, eukaryotic cells or prokaryotic cells?

A

Prokaryotic

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8
Q

What are the two types that prokaryotic cells are divided into?

A

Bacteria and archaea

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9
Q

Approximately when did multi-cellular organisms first appear?

A

600Ma

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10
Q

How old are Earth’s oldest rocks and what do these tell us about life conditions?

A

4000 - 2500 Ma.
These rocks are mostly cherts that would’ve been deposited underwater - suggesting abundant water on Earth.

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11
Q

How old is the oldest definite fossil (and oldest possible)?

A

Definite - 1.9Ba in Canada
Possible - 3.5Ba in Australia

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12
Q

What non-organic fossil from 3.5Ba provides fairly solid evidence of life?

A

Stromatolite fossil (rock formation formed by cyanobacteria)

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13
Q

What 4 elements comprise >90% of the non-living world?

A

silicon, oxygen, magnesium, iron

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14
Q

Why do silicon, oxygen, magnesium and iron play a relatively small part in living organisms?

A

Due to their high concentration in rocks.

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15
Q

Why are carbon and silicon both good candidates for being significant for life?

A

Both very reactive

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16
Q

What 3 elements comprise 98% of life forms?

A

Hydrogen, Oxygen, Carbon

17
Q

What are some advantages of carbon over silicon for life?

A
  • Can bond to itself and other elements (C-C bonds are a backbone of organic molecules).
  • Can bend and fold in more complex and pliable ways.
  • Can form solid, liquid, and gas compounds
  • Can form soluble and insoluble compounds
  • Can have multiple electrical states.
18
Q

What are the 4 major groups of molecules in life forms? What are their purposes?

A

Carbohydrates - fuel and structure
Lipids - fuel and membranes
Amino Acids - building blocks of proteins and structure
Nucleic acids - information storage and transport

19
Q

What are some proposed theories and locations for the origin of life?

A

Primordial broth
Evaporative intertidal lagoons
Deep sea vents
Clouds
Subsurface rock cracks
Mineral surfaces
Other planets
random primordial genes
RNA-world theories

20
Q

What was temperature and sun-levels like on the Earth pre-life?

A

30% dimmer sun, but reducing atmosphere and more CO2, so warmer Earth

21
Q

How must the building blocks of life have formed originally?

A

Abiotically

22
Q

What are two theories for the origin of life increasing in popularity?

A

Hydrothermal vents
Lightning