Geol30_08_Lecture_13b

Millions of years ago ma 1000 900 800 700 600 less

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Unformatted text preview: 00 900 800 700 600 Less severe? `Snowball Earth' glaciations green algae yellow-green g algae But life survived... All the documented eukaryotes that appeared before the first snowball event and still around today Thus, a lot of lineages survived red algae 9 2/19/2008 ...and in fact flourished just after 0.1 mm After the second snowball, some of the first see signs of abundant multicellular life (~600 Ma), including animals 0.5mm Animal embryos Also, microfossil assemblages before the 710 Ma-glacial Maevent are strikingly similar to an assemblage associated with and after the glaciation The same could be said for the 635 Ma-event Ma- Snowball Earth and Life: Conclusions Snowball Earth conditions did not markedly affect life: No mass extinction was exhibited in the fossil record Diversity was largely not affected Complex communities persisted `Slushball' Earth Still could be tough times for life Band of ice-free ocean in the vicinity of the equator iceNote: this is still a hotly debated issue, do not assume that my "conclusions" listed above are the last word on the subject More info in addendum and in the reading assignments on-line 10 2/19/2008 Late Neoproterozoic Life Biotic trends in the latest Neoproterozoic (~600 Ma to 542 Ma) Recall that from the origin of life to the end of the Precambrian, Precambrian life was in general microscopic was, general, Bacteria/archaea, acritarchs & early algae (possibly others?) Exception, carbonaceous compressions F...
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This document was uploaded on 06/04/2008.

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