You need to have a basic understanding of how things work in biology.
The optical properties of sea-water are of immediate importance in biology, as they affect the penetration of sunlight into the depths.
After completing his system (1896) Spencer continued to revise it, and brought out new editions of the Biology (1898-1899) and First Principles (1900).
The work achieved by Russian savants, especially in biology, physiology and chemistry, and in the sciences descriptive of the vast territory of Russia, is well known to Europe.
Comte's series or hierarchy is arranged as follows: (i) Mathematics (that is, number, geometry, and mechanics), (2) Astronomy, (3) Physics, (4) Chemistry, (5) Biology, (6) Sociology.