the science calorie (little c) is a measure of heat energy the food calorie (big C) is a measure of energy that we burn, but it is equal to 1,000 science calories so 1 big C is equal to 1,000 little c's.
Protists are a group made up of protozoa, unicellular algae, and slime molds. We will concentrate on the animal portion of this group: the protozoa (proto = first, zoa = animals).
Protozoa typically refer to heterotrophic, unicellular protists such as amoeba. The term algae is reserved for autotrophic protists. They can either be unicellular or multicellular aggregates.