GENERAL HISTOLOGY

Detailed explanation-1: -Probably the best-known Cambrian animals were trilobites-a group of armored invertebrates that no longer exist. They were abundant in shallow Cambrian seas, which covered much of the world. Paleontologists have identified many species of Cambrian trilobites.

Detailed explanation-2: -The plants of the Cambrian were mostly simple, one-celled algae. The single cells often grew together to form large colonies. The colonies looked like one large plant.

Detailed explanation-3: -In the early Cambrian, Earth was generally cold but was gradually warming as the glaciers of the late Proterozoic Eon receded. Tectonic evidence suggests that the single supercontinent Rodinia broke apart and by the early to mid-Cambrian there were two continents.

Detailed explanation-4: -These included brachiopods, which lived in shells resembling those of clams or cockles, and animals with jointed, external skeletons known as arthropods-the ancestors of insects, spiders, and crustaceans.