Cambrian Explosion. By, Sabrina Perrotta. What is the Cambrian Explosion?. Occurred around 500 to 540 Ma Time when fauna seemed to “Explode” and radiate into many branches Increase in abundance, diversity, and complexity of fauna. Cambrian Explosion Controversy.
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Lack of late Vendian fossils
Rarity of Precambrian infaunal traces
Species originate from some starting point
Complete absence of ancestors of modern groups at same time
Absence of coelomatic animals that made them
As groups originate they appear with out delay in the fossil recordFact vs. Inference
Shallow water environments
Low oxygen concentration in deep oceans
Inadequate supply of organic detritus
Deeper water environments
Deeper burrows due to increased competition
Increase in abundance, diversity, and complexityMore on trace fossils…
Shows increase in trace fossils after “explosion”, marking a change in hunting strategies, ability to penetrate substrates, new methods of locomotion
Deep water environments “flooded with trace fossils” due to increase in water depth and increase in biodiversity
Rise in trace fossils coincides with the timing of explosionMore on trace fossils..
The last common bilaterian arose between 573 and 656 Ma
Find that molecular rates in vertebrates slow down with increasing time because of gene duplication events increasing the number of interactors for each protein, slowing down the rate of molecular evolution
Support of the explosion reflecting the diversification of bilaterian phyla
7 genes looked at 300Ma:
ATPase 6, Cytochrome c, Cytochrome oxidase 1, Cytochrome oxidase 2,
beta hemoglobin, NADH 1,
and 18S rRNA
<= arthropods 300Ma
Body Plan Diversity
Development of predation foster evolution of mineralized skeletons
Seafloor sediment change , with decrease in microbial mats and an increase in homogeneity of oceans, cause an increase in disturbance to benthic organisms causing an increase in bioturbation
Extinctions (of microbial mats)
Adaptations (animals learn to adapt to new conditions by developing anchoring techniques)
Environmental Restrictions (certain fauna can only live in shallow water environments)
Do you believe there truly was an
“explosion” of rapid diversification?
Do you believe there was a gradual
Increase in diversification that occurred
slowly throughout time?