What does it mean to be an invertebrate?

invertebrate is a animal that does not have a back bone but may have a exoskeleton examples could be earthworm, jellyfish, snail and a spider because it has a exoskeleton a hard outer shell hope this helps

Vertebrates have a back bone like sea turtles , fish ,foxes and humans.

the old alchemists made significant contributions to science even though there starting premises were off a bit. their conclusions after failure would steer them into better directions for investigation. science is no more than close observation and the initial mistakes result in rethinking and retrying experiments.