Which organism appeared on earth first?

gastropods
horn corals
brachiopods
crinoids

If you are in a chronic state of anxiety but also suffer from moment of sudden, intense fear you are problably suffering. from

The table shows dates and appearance of index fossils. which rock layers can be dated most precisely? a) a layer containing both a fossil 4 and a fossil 3 b) a layer containing both a fossil 2 and a fossil 3 c) a layer containing both a fossil 1 and a fossil 4 d) a layer containing both a fossil 1 and a fossil 2

What is a group of organisms that are closely related and share similar characteristics