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Earth history and life - 29202 > Cambrian explosion > Flashcards

Cambrian explosion Flashcards

1
Q

What occurs between the Ediacaran and the Cambrian?

A

A step up in phyla and classes (Cambrian explosion)

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2
Q

What is there very little of after the Cambrian?

A

Existence of new phyla and classes (inhibited by hard fossil bias)

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3
Q

How is the Cambrian divided?

A

Into stages due to their being no formal recognition of the boundaries

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4
Q

What is the main difference between the Ediacaran and present day environments?

A

No life in the upper water column or within the sediment

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5
Q

What is Cloudina?

A

Present on the boundary between Ediacaran and Fortunian it is the earliest mineralising organism (worm like)

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6
Q

What is couldina a precursor?

A

To small shelly fauna which diversify in Cambrian stage 2 (Tommotian)

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7
Q

What are some examples of ‘small shelly fossils’?

A

Stem brachiopod
Problematica
Palaeoscolid worm

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8
Q

What are examples of fauna from Chenjiang China?

A

Anomalocaris
Arthropods

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9
Q

What fauna are an indicator of the Cambrian explosion?

A

Domination of arthropods

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10
Q

What formation occurred after Chenjiang?

A

Sirius Passet - Greenland

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11
Q

What is the boundary like at Sirius Passet?

A

An unconformity between stage 3 Cambrian and the Upper most Ediacaran

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12
Q

What fossils are present at Sirius Passet?

A

Microbial mat trace fossils

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13
Q

What fauna are present in the Sirius Passet?

A

Anomalocarids
Palaeoscolecids
Vetulicolians
Halkieria

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14
Q

What is the anomalocarid thought to be have been like in the Sirius Passet?

A

A filter feeder of plankton

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15
Q

What are the 2 taphonomy types in Siriuspasset?

A

Typical Sirius Passet preservation
Burgess shale type

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16
Q

What is preservation like with the typical Sirius Passet preservation?

A

Fauna mainly articulated
Mouldic
Infauna very rare
3D gut contents and body axes
Easily decomposed tissues not preserved (or not well-preserved)
No size limitations on preservation

17
Q

What is Burgess shale type preservation like?

A

Preservation as carbon/clay films
Fauna preserved sub-parallel to
bedding

18
Q

What formation occurred after Siriuspasset?

A

Emu Bay - South Australia

19
Q

What has one of the oldest records of with arthropods in Emu Bay?

A

Eyes

20
Q

What rock sequence formed after Emu Bay?

A

Burgess shale - British Columbia Canada

21
Q

What was the relative abundance of species in the burgess shale?

A

33% Arthropoda
22% Porifera
14% Algae
15% others

22
Q

How much were arthropods of relative abundance of species in the burgess shale?

A

60%

23
Q

What is the relative abundance of different lifestyles in the Burgess shale?

A

Epibenthic 64% (just above or on sediment)
Endobenthic 13%
Nektobenthic 12% (water column above sediment)
11% Nektonic (upper water column)

24
Q

What is the simplified burgess shale food web split into?

A

Active predators
Scavengers
Grazers and filter feeders
Algae

25
Q

What happens to the sediment as life progressed through the stages of the Cambrian?

A

The sediment geochemistry changes as it is exposed to oxygen (substrate revolution)

26
Q

How are hopeful monsters produced?

A

When genome duplication occurs producing redundant genes

27
Q

What evidence of the first predators are there?

A

Holes on the exterior of Cloudina showing shift from microbial mat to predation

28
Q

How are Uranium, Oxygen and Carnivorous fauna related?

A

Increased uranium in sediment record shows greater oxygen in environment which is needed for predation and increased activity

29
Q

How did oceanic ventilation occur?

A

Development of Eukaryotic bacteria created mixing of a ‘stagnant’ ocean full of cyanobacteria

30
Q

What are O2, Nutrients and substrate mobility like as you transition from land to sea?

A

All have greatest concentration near shore and decrease as distance form shore increases

31
Q

What happened that created high energy environments in the Cambrian?

A

Flooding creating high energy pools which might have had enough energy for diversification

32
Q

Why is it thought calcium shells were first developed?

A

Calcium is toxic so to get rid of a waste product

Earth history and life - 29202 (29 decks)

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