Experiments begin with an hypothesis that subjects itself to an experimental proof. The August Krough Principle states that there is an animal that is optimally suited for various experiments that will make experimentation easier. Experiments in physiology can also be at any level from molecular to whole animal. Ecologists are interested in energy budgets of animals. What is the energy cost of movement, reproduction, environmental adaption, etc.
Toxicologists are interested in the damage caused by chemicals at all levels.
Molecular Techniques Radioisotopes can be used to locate, purify, study transport, and quantify chemicals in living systems. Radioisotopes are handled as normal elements in living systems, yet they announce their presence by giving off radioactivity that can be detected by Gieger counters, scintillation counters and autoradiography. A monoclonal antibody is a protein that will attach to one specific part of a specific biochemical. It fits the shape of the chemical it attaches to. A polyclonal antibody is a group of antibodies that attach to a specific biochemical, but different antibodies attach to different places on the biochemical.