lunes, 28 de enero de 2013

Cell division

Cell division allows organisms to:
-         reproduce
-         grow
-         repair damage

Reproduction

-         Asexual
o       It is a process of producing offspring from only one parent to produce offspring that is genetically identical to the parent.
o       The cell divides into two identical cells
-         Sexual
o       It is a process of producing offspring by fusing a cell from one parent with the cell from another parent.
o       Each parent gives half of its genetic information (23 chromosomes each) to produce a gamete through the process of meiosis.

Growth

-         In order for multi-cellular organisms to grow, they increase the number of cells rather that increasing the size of the cell.
-         In order for cells to function, they require:
o       A source of energy, nutrients, water and gases
o       Must excrete carbon dioxide and waste
-         These substances substances enter and exit the cell through DIFUSSION
o       Movement from an area of high concentration to an area of low.
-         Most chemicals are dissolved in water, so cells must contains plenty of water
-         Water enters and leaves cell through OSMOSIS
o       The movement of water across a selectively permeable membrane toward an area of high solute concentration.
-         Difussion and osmosis must occur quickly.
o       The chemicals should be available to all parts of the cell in order to function properly.
o       Wastes are removed before they poison the cell.

Repair

-         The process of mitosis also allows organisms to regenerate damaged tissues.
-         Mitosis is also necessary for maintenance of the body
o       Cells are replaced if not functioning properly or when they die.