The primary mechanism by which organisms generate new cells is through cell division.
During this process, a single "parent" cell will divide and produce identical "daughter" cells.
In this way, the parent cell passes on its genetic material to each of its daughter cells.
First, however, the cells must duplicate their DNA.
Mitosis is the process by which a cell segregates its duplicated DNA,
ultimately dividing its nucleus into two.
Cell division is a universal process among living organisms.
In 1855, Rudolf Virchow, a German researcher,
made a fundamental observation about all living creatures:
every cell originates from another cell, or "omnis cellula e cellula," in the original Latin,
as author Myron Shultz recounts in a 2008 article in the journal Emerging Infectious Diseases.
The mechanisms of cell division vary between prokaryotes and eukaryotes.
Prokaryotes are single-celled organisms, such as bacteria and archaea.
They have a simple internal structure with free-floating DNA.
They use cell division as a method of asexual reproduction,
in which the genetic makeup of the parent and resulting offspring are the same.
One common mechanism of asexual reproduction in prokaryotes is binary fission.
During this process, the parent cell duplicates its DNA
and increases the volume of its cell contents.
Eventually, a fissure emerges in the center of the cell,
leading to the formation of two identical daughter cells.
The cells of eukaryotes, on the other hand, have an organized central compartment,
called the nucleus, and other structures, such as mitochondria and chloroplasts.
Most eukaryotic cells divide and produce identical copies of themselves
by increasing their cell volume
and duplicating their DNA through a series of defined phases known as the cell cycle.
Since their DNA is contained within the nucleus, they undergo nuclear division as well.
"Mitosis is defined as the division of a eukaryotic nucleus," said M. Andrew Hoyt,
a professor of biology at Johns Hopkins University, "
[though] many people use it to reflect the whole cell cycle that is used for cell duplication."
Like prokaryotes, single-celled eukaryotes, such as amoeba and yeast,
also use cell division as a method of asexual reproduction.
For complex multicellular eukaryotes like plants and animals,
cell division is necessary for growth and the repair of damaged tissues.
Eukaryotic cells can also undergo a specialized form of cell division called meiosis,
which is necessary to produce reproductive cells like sperm cells, egg cells and spores.