Across
1
Amplified beam of light
4
Element found in all living things
5
Nerve cell in the brain
7
Group of similar cells
8
Preserved remains of ancient life
10
Mass per unit volume
Down
2
Compound containing oxygen
3
Smallest unit of an element
5
Center of an atom or cell
6
Gas essential for breathing
9
Absolute temperature scale unit
11
The Red Planet