Cambrian Explosion Flashcards
Explosion in morphology (& trophic scaling), not genetics
Prokaryotes (bacteria/archaea)- most genetic and functional diversity, primary producers (make their own sugar) thrive
Eukaryotes are limited in genetic diversity, but their morphology is expansive
Trace fossils
Not organism itself, but a record of its activity
- Bilaterian animals from Ediacaran times- present by ~630 Ma
- Feeding traces- traces on sea floor demonstrate movement in search of food (likely dead organic matter)
- Long term C cycle- feeding traces reduces potential for organic matter burial, weakening organic matter sink
First carbonate shells at 549 Ma
- Inorganic carbon
- Ediacara- Cloudina, first biomineralized organism (~549 Ma)
Advantages of hard parts:
- Protection from predators- on land, protection from desiccation
- Anchoring (for immobile organisms)
- For predators, useful for attacking and feeding
- Shells create a holding tank for filter feeding
- Helps mobility (anchors for muscles)
Drawbacks of hard parts:
- Requires energy to create hard parts
- If anchored, limits mobility- less choice in face of environment change/predators
- For shelled organisms, slows down gas exchange (less oxygen diffusion in tight shell) and waste exchange
SSF
(Small shelly fossils)
Early Cambrian biomineralized fossils
Mass extinction at Proterozoic-Phanerozoic boundary?
- Created ecospace for bilateral animals to fill in
- Parallel to other mass extinction events
Carbon cycle upheaval around Proterozoic-Phanerozoic boundary
Changes in δ13C of surface earth system- large scale changes (as large as entire rest of the Phanerozoic)
Indicates changes/perturbations in carbon cycle
- Less OM burial, living biomass is killed and decomposes- C12 can go elsewhere on surface earth
Burgess Shale
Middle Cambrian (~505 Ma)
- Contains soft-bodied fossils
- Interpreted environment (where these animals were deposited)- base of a reef
- Anomalocaris
Burgess shale is not unique- Ordovician lagerstatten (80-100 Ma after Burgess shale)
- Still showing strange forms- indicates these were successful for a long time
