Asexual reproduction is advantageous in allowing beneficial
combinations of characteristics to continue unchanged and in
eliminating the often vulnerable stages of early embryonic
growth. It is found in most plants, bacteria, and protists and
the lower invertebrates. In one-celled organisms it most
commonly takes the form of fission, or mitosis, the division of
one individual into two new and identical individuals. The cells
thus formed may remain clustered together to form filaments (as
in many fungi) or colonies (as in staphylococci and Volvox).
Fragmentation is the process in filamentous forms in which a
piece of the parent breaks off and develops into a new
individual. Sporulation, or spore formation, is another means of
asexual reproduction among protozoa and many plants. A spore is
a reproductive cell that produces a new organism without
fertilization. In some lower animals (e.g., hydra) and in
yeasts, budding is a common form of reproduction; a small
protuberance on the surface of the parent cell incre