Chapter 3.2Cell Division

Life Science

What causes organisms to grow??

Many organisms start as one cell…what happens to these cells?– Cells divide!! One becomes two, two

becomes four… Multi-cellular organisms grow because

of CELL DIVISION!

Cell Division Cell Division- increases the total

number of cells and causes multi-cellular organisms to grow and develop.

3 Functions:

1. Growth

2. Development

3. Repair

The Cell Cycle Cells contain periods of formation,

growth and development, and death called a life cycle.– Forms, Grows/Develops, Dies.

The length of the cycle depends on the type of cell.

CELL CYCLE: Page 81

cell grows and carries out normal activities; organelles duplicate

DNA replicates and chromosomesduplicate

cell grows and prepares for mitosis

Mitosis

Mitosis (mi TOH sus) – process in which the nucleus divides to form two identical copies of cellcopies of cell.

Do YOU remember the steps or

phases of Mitosis?

BEFORE MITOSISInterphase

Interphase - phase where Eukaryotic cells spend most of their “life”– A period of growth and development.

– Cell duplicates its chromatin and prepares for cell division.

Cell is not dividing***

Chromatin, Chromatid, Chromosome …

MITOSIS BEGINSProphase

Prophase “P” for Pairs– Nucleus disappears– Centrioles - two small structures that

move to opposite ends– Spindle fibers - (threadlike) begin to

stretch across the cell.

Metaphase Metaphase- “M” for

Middle– Chromosomes line up across the center

of the cell – Spindle Fibers attach to the centromere.

Anaphase

Anaphase- “A” for Apart– Centromere divides – Chromatid Pairs separate and moves to

opposite ends of the cell– Spindle Fibers pull similar to a fishing rod

Telophase Telophase- “T” for Two

– Spindle Fibers disappear

– New Nucleus is formed (nuclear membrane)

– Two Cells form.

AFTER MITOSIS Cytokinesis- the division of the parent

cell’s cytoplasm.

(Page 85) In animal cells, the cell is pinched

into two identical daughter cells.

http://www.cellsalive.com/mitosis.htm

Results of Mitosis Each cell in your body (except sex

cells) has the same number of 46 chromosomes (23 pairs)

Allows growth and replaces damaged cells