Across
1
Naturally occurring inorganic solid
5
Gas essential for breathing
7
Compound containing oxygen
8
Group of similar cells
9
Element found in all living things
15
Solid with repeating atomic pattern
Down
2
Biological catalyst
3
Curved glass that refracts light
4
Center of an atom or cell
6
Precious yellow metallic element
10
The Red Planet
11
Force that attracts objects together
12
Tissue that contracts for movement
13
Unit of energy
14
Unit of heredity