Set 4: Central Ideas (Advanced)
Explanation
PASSAGE
The following text describes the 'Cambrian Explosion'. The Cambrian Explosion, occurring approximately 541 million years ago, was a relatively short evolutionary event during which most major animal phyla appeared in the fossil record. Before this, life was simple, composed mostly of individual cells or small multicellular organisms. The event is characterized by the rapid diversification of life forms and the emergence of complex body plans, hard shells, and exoskeletons. Hypotheses for its cause include increased oxygen levels and the evolution of eyes.
What characterizes the Cambrian Explosion?
Detailed Explanation
Choice B is correct. The text notes 'rapid diversification of life forms and the emergence of complex body plans.'
Key Evidence:
• "rapid diversification of life forms"
• "most major animal phyla appeared"
Why others are wrong: A (Wrong era (Cretaceous-Paleogene)), C (Happened much earlier), D (Happened later).