1. which of the following phyla have representatives that exhibit radial symmetry throughout their entire lives?

Cnidarians have representatives that exhibit radial symmetry throughout their entire lives. Cnidarian, also called coelenterate, include the corals, hydras, jellyfish, sea anemones, etc. Cnidarians are radially symmetrical (similar parts are arranged symmetrically around a central axis).

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.