2.9 - Specialization experimentally, cells maintained in tissue culture will divide 50 times,

regardless of when they are frozen and thawed

cell division in organisms is determined by specialization

dermal cells divide more than muscle, nerve, or secretory cells

spermatocytes and cancer cells divide continuously

specialized sperm stop dividing while cancer cells divide too rapidly to specialize and thus lose their normal functions

the cell clock is turned on when differentiation (specialization) begins

SPECIALIZED CELLS 2.9

• Many complex organisms, such as a human being or a

maple tree, begin life as a single fertilized egg or a single

cell.

• The cells in a complex organism are not all identical. They have

been created to perform specific functions, such as digesting food,

fighting disease, or coordinating the body’s movements.

• Specialized cells have physical and chemical differences that allow each type

to perform one job very well. For example, the specialized cells in the photo help

keep dirt out of the lungs. The orange goblet

cells secrete mucus, while the hair-like

extensions of the cells (called cilia) move

the mucus along the trachea to remove

inhaled dust and dirt.

specialized cells

Specialized Cells

Blood cells muscle cells fat cells nerve cells

Specialized Cells

Root cell xylem chloroplastphloem

White Blood Cells

Sperm Cell

Skin Cells

Bone Cells