Exam 12: Paleozoic Life History Invertebrates

Trilobites make excellent guide fossils.

Pelagic organisms live in the water column above the seafloor.

A stratified ocean in the Late Permian could have been caused by ____.

The end-Devonian mass extinction affected polar and high-latitude organisms the most.

The first evidence of shelled organisms is calcareous tubes found with the Ediacaran fauna.

Scientists have several hypotheses for why the Cambrian explosion occurred. Explain three of the hypotheses.

An extinct group of arthropods with a body divided into three lobes is a(n) ____.

Phytoplankton are primary producers.

Trilobites, an abundant organism during the Early Paleozoic and less abundant during the Late Paleozoic, survived to the Cenozoic.

Greatly accelerated extinction rates resulting in marked decrease in biodiversity are ____.

The Cambrian explosion refers to ____.

Burrowing worms are examples of planktonic organisms.

Organisms that move on the seafloor are called ____, while organisms that do not move are called ____.

Which group feeds on microscopic plants, animals, and nutrients in water?

Consider an early reef-builder of the Cambrian, the archaeocyathid. Using correct terminology for marine ecosystems, classify this organism on where it lives, how it gets around, and how it feeds. How does the lifestyle of archeocyathids compare with that of Cambrian trilobites?

Diatoms and algae are examples of phytoplankton.

Describe the components of the present-day marine ecosystem. What types of organisms populate this ecosystem? Give specific examples.

Which characteristic does not apply to trilobites?

Describe and discuss the marine communities of the Ordovician, Silurian, and Devonian. How do they compare with present-day marine communities?

Three of the five largest mass extinctions occurred at the end of the ____.