Theme 5C Flashcards

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1
Q

What is the hypothesis for the origin of biological molecules

A

Originated in the ocean
Ocean environment was reducing - sulphur bacteria/thermophiles habitat
Vents provide habitats

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2
Q

What was the Urey Miller experiment

A

Simulated early Earth conditions and tested chemical origin of life
2% of carbon was amino acids 13/22 used in living cells

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3
Q

How old is the earth and when did life start to evolve

A

Earth is 4.5 billion years old
Unicellular prokaryotes arrived 3.5 bya
Simple multicellular life 2.1 bya
Complex multicellular life 650 mya

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4
Q

What is the importance of the shift to an oxygen atmosphere

A

Allowed for higher metabolic rates and a larger body size

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5
Q

Why was the rise of oxygen slow

A

Long period of anoxygenic photosynthesis
Oxygen was a result of Cyanobacteria
Was an oxidizing agent, so would react with reducing agents before it was able to accumulate at all
Was only when ocean became a CO2 sink did oxygen start to accumulate

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6
Q

What was the great oxygenation event

A

Free oxygen accumulates about 2.5 bya in atmosphere with huge increase 850 mya
Evidence: banded iron formations abundant 2.5 - 1.8 bya, declined after, major changes in rock types, hydrated and oxidized minerals

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7
Q

What were the first eukaryotes

A

Evolved from a symbiotic relationship between mitochondria and plastids (chloroplasts)
Larger then prokaryotes, have a nucleus, membrane bound organelles

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8
Q

What was the evidence for the symbiotic relationship between mitochondria and plastids

A

Organelles bound by membranes
Organelles have own DNA sequence separate from DNA in nucleus
Mitochondrial DNA is similar to bacteria/chloroplast DNA
Mitochondria and bacteria both replicate by pinching

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9
Q

How long ago was the ediacaran fauna

A

Ended 640 million years ago
All organisms are extinct

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10
Q

How long ago was the palaeozoic era

A

542-252 million years ago

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11
Q

How long ago was the Mesozoic era

A

252-65 million years ago

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12
Q

How long ago was the Cenozoic era

A

65 million years ago to present

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13
Q

What was the Cambrian explosion

A

Occurred in the palaeozoic era (about 530 mya)
Rapid appearance of many groups of organisms, started with small shell parts
Include evidence of arthropods, echinoderms and features of many modern groups appear (head, mouth, eyes, limbs)
Very high mutation rate, lots of diversity

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14
Q

What is a mass extinction

A

Rate of extinction great,y exceeds rate of speciation
Has to be more the 75% of all species of extinct

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15
Q

Why is mass extinction important

A

Niches are cleared and ecological opportunities are made available
Leaves low diversity of once diverse lineages

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16
Q

What was the advantage of chemolithotrophy

A

Allows prokaryotes to maximize ATP production by using different “food” source (like different electron donors)

17
Q

When was the archaean to Proterozoic era and what happened

A

4 billion to 500 million years ago
Prokaryotes, eukaryotes and multicellularity
Great oxygenation event

18
Q

What and when are the first known prokaryotes

A

Cyanobacteria, 3.2 to 3.4 bya
Stromatolites appear in fossils dating back to 2.7 bya

19
Q

How do Cyanobacteria obtain energy

A

Photosynthesis
Produce gaseous oxygen —> convert reducing atmosphere into oxidizing one

20
Q

Why was the Cambrian an explosion of life

A

Genetic diversity
Increasing O2 levels of eukaryotic algae
Shift in ocean chemistry favouring production of calcium carbonate