Chapter 3.2 Cell Division Life Science. What causes organisms to grow?? Many organisms start as one...

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