GATE-2018 (24) :Wyllie – Time average equation

CSIR-NET

23. Which of the following geological time intervals witnessed the first appearance of skeletal organisms in the Earth's history?

A) Triassic

B) Cambrian

C) Devonian

D) Cretaceous

Answer: B

Explanation:

Phanerozoic Eon - 540 mya through today- organisms with skeletons or hard shells.

Paleozoic Era - 540 to 248 mya

Cambrian Period -540 to 200 mya -The Age of Trilobites.