The Boundary Between the Archean and Proterozoic Is Marked by Changes

question 65

Multiple Choice

The boundary between the Archean and Proterozoic is marked by changes in ____.

• A) fossil assemblages
• B) crustal evolution styles
• C) atmospheric composition
• D) oceanic composition
• E) atmospheric temperatures

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Definitions:

Flatworms

A group of invertebrates belonging to the phylum Platyhelminthes, characterized by their flattened bodies, lack of body cavity, and simple organ systems.

Radially Symmetrical

An attribute of organisms that can be divided into identical halves along any plane that passes through the central axis, common in many jellyfish and sea anemones.

Cnidarians

A phylum of aquatic invertebrate animals that includes jellyfish, corals, and sea anemones, characterized by their specialized stinging cells called cnidocytes.

Echinoderms

A phylum of marine animals characterized by radial symmetry, a calcareous skeleton, and a complex water vascular system, including starfish, sea urchins, and sea cucumbers.