CAMBRIAN EXPLOSION

Question 1

Why are Sponges unique?

Answer 1

You can put them through a wood chipper and they’ll still be doing mighty fine. Lack tissue grade in their body, so they have the ability to regenerate. They straddle the boundary between unicellular and multicellular organisms (metazoans).

Question 2

What is the “Cambrian Explosion”?

Answer 2

All major phyla with hard parts suddenly appear! The sudden appearance of fossils in the lowest strata.

Question 3

Trilobites

Answer 3

The most common and diverse invertebrates in the cambrian.

Question 4

Charles Dolittle Walcott & the Burgess Shale

Answer 4

Gorgeously preserved soft bodied impressions of fossils from the mid-Cambrian (505 Ma)

Question 5

Possible causal mechanisms for the Cambrian explosion

Answer 5

Intense chemical weathering of rocks supersaturated the ocean with ions, which marine organisms may have used to grow shells.
Change in seawater chemistry due to continental denudation
Active predators may have made organisms for protective shells
Maybe the rise in oxygen levels also contributed
BUT largely unknown!

Question 6

Secondary increase in atmospheric oxygen

Answer 6

Permitted larger multicellular organisms to evolve

Question 7

Ecological Arms Race between predators (Anomalocaris) and prey

Answer 7

Maybe the rise of active predators fueled animals to form protective shells.

Question 8

Great Unconformity – what is it?

Answer 8

Universal missing time in the rock record. Probably due to intense weathering of the rocks.

Question 9

Chemical weathering of silicate minerals in continental rocks, seawater chemistry & biomineralization of skeletal hard parts

Answer 9

Intense weathering occurs -> calcium and magnesium ions leech into ocean -> maybe used to create hard parts (calcium carbonate shells)?