AD 4

When was the ediacaran period of time?

635-542mya

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Key features of bilaterians (3)

Symmetrical, Triploblasty, cephalisation

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3 main types of bilaterian protostomes

lophotrochozoa, ecdysozoa, deuterostomes

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How where organisms preserved in the burgess shale?

deep sea bed buried by fine sediment so no o2 leads to preservation of C films and decay stopped due to different minerals/compounds present

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How does fossilisation in ediacaran and cambrian change?

low S and high alkilinity change so preservation in burgess shale, less fossilisation after cambrian, not much known pre cambrian

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what are the possible causes of the cambrian explostion (3)

Environmental changes, ecological changes or gene variation

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What organisms are part of the total group classification?

living representatives and all extinct relatives

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What organisms are part of the crown group classification?

living representatives and closely related organisms

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what organisms are part of the stem group classification?

only extinct organsims- they have closer relations to most common ancestor then living organisms

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Name 8 different groups of organisms found in the burgess shale

Porifora, annelida, mollusc, arthropoda, deuterostome, cnidaria, priapulida, onychophora

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