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evolution > Origins of Early Life > Flashcards

Origins of Early Life Flashcards

1
Q

How old is the earth?

A

4.6by

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2
Q

How did the earth form?

A

by the gradual accumulation of 9dust and larger objects

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3
Q

When are the earliest fossil evidence for life dated?

A

3500MYA

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4
Q

By what point was earth cool enough for life to exist?

A

3800MYA

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5
Q

What is the Panspermia theory?

A

suggests that life on earth didn’t originate on earth, but arrived on a meteorite from another planet.

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6
Q

What are the problems with the panspermia theory?

A

No other planet has been found with conditions suitable for life, and the bombardment of meteorites created conditions that would have killed any early life forms

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7
Q

What is the evidence that eukaryotes evolved from prokaryotes?

A

prokaryotes apper earlier in the fossil record
Prokaryotes simpler in virtually every aspect
Have fundamental similarities

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8
Q

What are the similarities between Prokaryotes and Eukaryotes?

A

method of transmitting information is in the triplet code

Aino acids are laevorotary, nucleic acid sugars are dextrorotary

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9
Q

What is LUCA?

A

Latest Universal Common Ancestor, suggests all recent populations and everything on earth have one common descent.

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10
Q

What are the similarities between all lineages of extant organisms?

A

DNA, RNA, Pseudogenes, amino acids

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11
Q

What are pseudogenes?

A

genes that have lost their function, no longer code for a protein

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12
Q

What is the Miller-urey experiment?

A

Conditions of early earth simulated in the lab to see what chemicals it would yield and if these would be able to support early life?

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13
Q

What chemicals were created in the miller Urey experiment?

A

Amino acids, Purines/Pyrimidines, Sugars, Porphyrins, Tar like substances

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14
Q

What were the possible energy sources on earth?

A

Sun
Radioactivity
Lightning
Volcanoes

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15
Q

What are the four main steps in the creation of the earliest cells?

A

1 - abiotic synthesis of small organic molecules
2 - joining of small molecules into macromolecules
3 - Packing of molecules into probionts
4 - Origin of self replicating molecules

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16
Q

What are probionts?

A

An aggregation of organic molecules, surrounded by a membrane, that abiotically coalesces into resemblances of living matter

17
Q

What did self replicating material make possible?

A

Inheritance

18
Q

What was the first genetic material?

A

RNA

19
Q

What was discovered that scientists base the origin of early life on?

A

Self splicing RNA, capable of catalysing their own excision from parent molecules

20
Q

What is the primordial soup theory?

A

life began in an ocean as a result of a combination of chemicals from the atmosphere and some form of energy to make amino acids etc.

21
Q

What are chemoheterotrophs?

A

Carbon source and energy both come from organic compounds

22
Q

What are chemoautotrophs?

A

Carbon source from Co2, energy from inorganic chemicals

23
Q

What are photoheterotrophs?

A

Carbon source from organic material, energy from light

24
Q

What are photoautotrophs?

A

Carbon source from CO2, energy from light

25
Q

What are Obligate Aerobes?

A

requires oxygen

26
Q

What are Obligate anaerobes?

A

only anaerobic respiration

27
Q

What are facultative anaerobes?

A

both aerobic and anaerobic respiration

28
Q

What are the three types of evidence for presence of prokaryotic life?

A

Fossil Stromatolites, Fossil microorganisms, Carbonaceous matter

29
Q

What are stromatolites?

A

layered rocks that form when certain prokaryotes bind thin films of sediment together, form in hyper saline conditions

30
Q

Where is evidence of fossilised microorganisms found?

A

silicified in cherts, and acritarchs

31
Q

How can carbonaceous matter be chemically tested for evidence of early life?

A

Rubisso has preferential carbon isotope uptake -C12 is better, so signals seen in isotopic ratios in carbonaceous remains

32
Q

What do cyanobacteria produce as a byproduct of metabolism?

A

Oxygen

33
Q

How is most atmospheric 02 produced?

A

Photosynthesis step of splitting water

34
Q

What happened when photosynthesis first evolved?

A

free oxygen dissolved into surrounding water, very reactive

35
Q

What are the early oxygen sinks?

A

Volcanic gases, dissolved iron in the ocean, microorganisms carrying out respiration aerobically

36
Q

What are BIFs?

A

banded iron formations, formed when oxygen dissolved into the ocean and reacted with iron to precipitate out as an oxide. , O2 could only gas out once all iron was reacted and sea is saturated with oxygen

evolution (11 decks)

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