Chapter 3.2 Cell 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 copies of cell  Mitosis (mi TOH sus) – process in which the nucleus divides to form two identical copies of cell.  Do YOU remember the steps or phases of Mitosis ?

BEFORE MITOSIS Interphase  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 BEGINS Prophase  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.

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