Across
1
Biological catalyst
5
Group of similar cells
6
Substance with pH above 7
7
Naturally occurring inorganic solid
8
Element found in all living things
9
Path of a planet around the sun
11
Basic unit of life
Down
2
Tissue that contracts for movement
3
Smallest unit of an element
4
Blocking of light by a celestial body
10
Precious yellow metallic element
12
Positive particle in nucleus
13
Glass that splits light into spectrum
14
Curved glass that refracts light
15
Ball of burning gas in space