All of the following have an internal skeleton except
a. sand dollars.
b. sand fleas.
c. sea stars.
d. sea lilies.

Four types of motile cells in human body?

What was the land like over 500 million years ago? what was under the sea?

What evidence supports the law of conservation of energy? a) mechanical energy is converted to chemical energy during photosynthesis. b) oxygen is made from the breakdown of carbon dioxide during photosynthesis. c)energy is absorbed by chlorophyll and becomes chemical energy during photosynthesis. d)the sun gives off light energy that is absorbed by plants.