Across
1
Infectious microscopic agent
3
Basic unit of life
4
Biological catalyst
7
Preserved remains of ancient life
8
Particle of light
9
Solid with repeating atomic pattern
Down
2
Tissue that contracts for movement
5
Gas essential for breathing
6
Substance with pH below 7
10
Form of thermal energy
11
Nerve cell in the brain
12
Path of a planet around the sun