Lecture 11 Flashcards
Significance of Ediacaran organisms
1st appearance of macroscopic life
What does Proterozoic mean?
Earliest life
Ediacaran Biota
Rapid radiation after an ice age (the Cryogenian)
Widely distributed
Ediacaran Biota forms
Discs, tubes, “quilted mattresses”, “sea pens”
Ediacaran Biota relationships
Disputed; animals, fungi, Vendozoa
Some forms are likely related to modern metazoans
Ediacaran Biota stratigraphic range
Late Ediacara-Cambrian
Cloudina age
Same age as Ediacaran Biota but don’t occur with it
Where is cloudina found?
With stromatolites
Shape of cloudina fossils
Conical
Trend of trace fossil record from Ediacaran to Cambrian
More abundant, more complex, bigger, and deeper into sediment
Small shelly fossils size
um to mm
Small shelly fossils age
550 Ma
Small shelly fossils significance
Evidence for Cambrian radiation
Cambrian explosion broadly
Appearance of most major animal phyla
5 main points of Cambrian explosion
Origin of high-level animal groups
Diversification of animal groups
Increase in morphological disparity
Emergence of complex food webs
Biomineralization
Significance of Burgess Shale in Cambrian Explosion
Origin of many animal groups in the early Cambrian
Examples of importance of Burgess Shale in Cambrian Explosion
Pikaia (early chordate)
Sponges
Marella (arthropod)
Cambroernid (now extinct)
3 categories of inter-dependent hypotheses as to why the Cambrian Explosion occurred
Changes in abiotic/environmental conditions
Changes in the geochemistry of the oceans
Developmental/genetic
Basic causes of the Cambrian Explosion
Tectonism (rifting)
Rise in oxygen levels
Changes in geochemical conditions of the oceans
Sea level rise
“Arms race” between organisms
Skeleton development of certain organisms
Prompted adaptation of other organisms in response
