Download Do you know that most living things start out as a single cell

Do you know that most living things start out as a single cell?
Humans, dogs, fish, and trees all start from a single cell. This single
cell multiplies and forms a living thing. Living things can be made
of trillions of cells. So, how does a single cell make trillions of cells?
All cells are made from other cells. New cells are made when an old
cell divides in two. Each of these two cells can then divide to make
two more cells. This process is called cell division. As long as each
new cell continues to divide, a single cell can become many cells.
Cell division begins inside the cell. All cells contain
instructions for carrying out their activities.
These instructions are found in the nucleus of the cell.
Before cell division starts, a cell copies the
information in its nucleus. Then the nucleus breaks
into two pieces. Each piece has a copy of the nucleus's
information. The copies move to opposite sides of the
cell. The middle of the cell starts to pinch inward.
Then a nucleus rebuilds in the new cell. The cell
finally pinches through to make two new cells. Each
new cell has a nucleus with a complete copy of the
cell's information. And, each new cell is identical to
the old cell.
Your body is always making new cells. It uses new cells to heal cuts
and injuries, to replace dead cells, and to grow. When you have a
tear in your skin, your cells undergo cell division to cover the
wound with new cells. Cell division of skin cells can also replace
dead and dried out cells. As millions of cells in your body divide,
you grow. Cell division is an important process. Without cell
division, living things could not survive.
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