3. Early planet; early life

Question 1

When did the Earth form?

Answer 1

4600Ma

Question 2

When was the moon formed?

Answer 2

Approx 4500Ma

Question 3

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

Answer 3

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.

Question 4

What is the approximate size of a prokaryotic cell?

Answer 4

0.1-10μm

Question 5

What is the approximate size of a eukaryotic cell?

Answer 5

10-100μm

Question 6

What are the key features of a prokaryotic cell?

Answer 6

No nucleus, organelles are not membrane-bound

Question 7

Which evolved first, eukaryotic cells or prokaryotic cells?

Answer 7

Prokaryotic

Question 8

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

Answer 8

Bacteria and archaea

Question 9

Approximately when did multi-cellular organisms first appear?

Answer 9

600Ma

Question 10

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

Answer 10

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

Question 11

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

Answer 11

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

Question 12

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

Answer 12

Stromatolite fossil (rock formation formed by cyanobacteria)

Question 13

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

Answer 13

silicon, oxygen, magnesium, iron

Question 14

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

Answer 14

Due to their high concentration in rocks.

Question 15

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

Answer 15

Both very reactive

Question 16

What 3 elements comprise 98% of life forms?

Answer 16

Hydrogen, Oxygen, Carbon

Question 17

What are some advantages of carbon over silicon for life?

Answer 17

• 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.

Question 18

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

Answer 18

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

Question 19

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

Answer 19

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

Question 20

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

Answer 20

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

Question 21

How must the building blocks of life have formed originally?

Answer 21

Abiotically

Question 22

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

Answer 22

Hydrothermal vents
Lightning