A micronucleus divides by mitosis and contains the genetic information of the cell in normally shaped chromosomes. As many as 80 micronuclei may occur in a single cell. The single macronucleus in a cell contains multiple copies of DNA divided into small pieces. They replicate by elongating and constricting. Macronuclei are essential for routine cellular functions.
Paramecium are a free-living, freshwater genus.
Like most ciliates, Paramecium undrego a special process called conjugation. During conjugation, individuals from two different strains align longitudinally and exchange nuclear material. This exchange seems to rejuvenate the individuals and is usually followed by frequent mitosis. Phylum Rhizopoda Amoebas occur throughout the world in marine, freshwater, and terrestrial environments. The unifying characterisic of this phylum is the presence of pseudopods, which are movable extensions of cytoplasm used for locomotion and gathering food.