3. Early planet; early life Flashcards
When did the Earth form?
4600Ma
When was the moon formed?
Approx 4500Ma
What is the period of 3900Ma to 3800Ma referred to as in Earth’s history? What does it mean for life on earth?
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.
What is the approximate size of a prokaryotic cell?
0.1-10μm
What is the approximate size of a eukaryotic cell?
10-100μm
What are the key features of a prokaryotic cell?
No nucleus, organelles are not membrane-bound
Which evolved first, eukaryotic cells or prokaryotic cells?
Prokaryotic
What are the two types that prokaryotic cells are divided into?
Bacteria and archaea
Approximately when did multi-cellular organisms first appear?
600Ma
How old are Earth’s oldest rocks and what do these tell us about life conditions?
4000 - 2500 Ma.
These rocks are mostly cherts that would’ve been deposited underwater - suggesting abundant water on Earth.
How old is the oldest definite fossil (and oldest possible)?
Definite - 1.9Ba in Canada
Possible - 3.5Ba in Australia
What non-organic fossil from 3.5Ba provides fairly solid evidence of life?
Stromatolite fossil (rock formation formed by cyanobacteria)
What 4 elements comprise >90% of the non-living world?
silicon, oxygen, magnesium, iron
Why do silicon, oxygen, magnesium and iron play a relatively small part in living organisms?
Due to their high concentration in rocks.
Why are carbon and silicon both good candidates for being significant for life?
Both very reactive