the dried excrement of fish-eating sea birds, deposited in rocky coastal regions of South America: contains the urates, oxalates, and phosphates of ammonium and calcium; used as a fertilizer.
In prokaryotes there is only one rather simple type of cell division, which produces two identical daughter cells from one progenitor cell. This is asexual cell division, since it involves no sexual union of different individuals.
Often confused with adult stem cells, progenitor cells are early descendants of stem cells that can differentiate to form one or more kinds of cells, but cannot divide and reproduce indefinitely.