In science, a theory is an explanation for some phenomenon that is based on
observation, experimentation, and reasoning. one important theory in biology is the
cell theory. what kinds of observations led to the development of the cell theory?
a. testing of first vaccines
b. discoveries of fossil bacteria
c. isolations of dna and rna
d. microscopic views of plants and animals

Match the following terms and definitions. the transformation of a larva to an adult; occurs only in animals having great differences in form between the larva and adult pupa 2. type of mammal that lays eggs monotreme nymph the part of certain insect life cycles in which the young animal has no wings or reproductive organs the developmental stage between larva and adult in insects undergoing metamorphosis metamorphosis 5. the male gonad which produces sperm testes