Cambrian Explosion

Question 1

Why are sponges unique?

Answer 1

• you can put them through a wood chipper and they will be just fine
• lack tissue grade in their body so they have the ability to regenerate
• straddle the boundary between unicellular and multicellular (matazoans)

Question 2

What is “The Cambrian Explosion”?

Answer 2

all major phyla with hard parts suddenly appear

• 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 and the Burgess Shale

Answer 4

• geographically preserved soft bodied impressions of fossils from the mid-Cambrian (505 ma)

Question 5

Possible Casual Mechanisms for the Cambrian Explosion

Answer 5

• intense chemical weathering of rocks supersaturated the oceans with ions which marine organisms use to grow shells
• change in the seawater chemistry due to continental denudation
• active predators may have made organisms form protective shells
• maybe a rise in oxygen levels

WHO KNOWS?

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

Answer 8

universal missing time in the rock record

• probably due to an intense weathering of the rocks

Question 9

Chemical Weathering of Silicate Minerals in Continental Rocks, Seawater Chemistry and Biomineralization of Skeletal Hard Parts

Answer 9

• intense weather occurs, calcium and magnesium ions leech into oceans
• maybe used to create hard parts (calcium carbonate shells)