LEARNING GOALS: -Use terminology related to living things -Describe the cell cycle in plants and animals -Describe the process of mitosis and explain the importance for growth of cells and repair of tissues SUCCESS CRITERIA: Identify and describe the stages of the cell cycle Identify and describe the stages of cell division Explain the reasons why cells divide

CELL CYCLE/ CELL DIVISION

Minds-On: Cells Must Divide! DID YOU KNOW! Red blood cells are produced at a rate of 2 million cells per second. In a year? You make x Huh? That’s red blood cells in one year.

Why do cells divide? 1. Cell Division for Growth 2. Cell Division for Repair

1. Cell Division for Growth Why can’t cells just grow larger for growth? Cell size is limited

Cell Size is Limited… Surface Area: the area of the cell over which all nutrients must enter and all wastes must leave. Cell Volume: determines how much the cell holds *Volume increases faster than surface area.

2. Cell Division for Repair Every day, our body sheds millions of dead skin cells. Your body replaces red blood cells every 120 days. If a bone breaks, you need new bone cells to repair the damage.

SUMMARY: Why is cell division important? 1) Growth: enables organisms to grow from a single cell into a multi-celled organism. 2) Maintenance: produces new cells to replace worn-out or dead cells 3) Repair: regenerates damaged tissue. Regeneration is the ability to replace damaged or lost body components.

The Cell Cycle Cells alternate between stages (phases) of dividing and not dividing. This sequence of events is called the cell cycle For most cells the cell division phase is only a small part of the cell cycle

The Cell Cycle The stage between cell divisions is called INTERPHASE G1 (Growth) S (Synthesis – DNA replication) G2 (prepares for cell division) Cell Division Mitosis Cytokinesis

Stage 1 of Cell Division: Mitosis Mitosis: the process of dividing the nuclear material Stage 2 of Cell Division: Cytokinesis Cytokinesis: the process of dividing the cytoplasm and organelles.

Mitosis is divided into four phases. 1.Prophase(P) 2.Metaphase(M) 3.Anaphase(A) 4.Telophase(T)

Prophase is characterized by four events: 1.Chromosomes condense and are more visible. 2.The nuclear membrane (envelope) disappears. 3.Centrioles have separated and taken positions on the opposite poles of the cell. 4.Spindle fibers form and radiate toward the center of the cell.

PROPHASE

Metaphase (the shortest phase of mitosis) is characterized by two events: 1.Chromosomes line up across the middle of the cell. 2.Spindle fibers connect the centromere of each sister chromatid to the poles of the cell.

METAPHASE

Anaphase is characterized by three events: 1.Centromeres that join the sister chromatids split. 2.Sister chromatids separate becoming individual chromosomes. 3.Separated chromatids move to opposite poles of the cell.

ANAPHASE

Telophase (the last phase of mitosis) consists of four events: 1.Chromosomes (each consisting of a single chromatid) uncoil. 2.A nuclear envelope forms around the chromosomes at each pole of the cell. 3.Spindle fibers break down and dissolve. 4.Cytokinesis begins.

TELOPHASE

Cytokinesis Cytokinesis is the division of the cytoplasm into two individual cells. The process of cytokinesis differs in plant and animal cells. In animal cells the cell membrane forms a cleavage furrow that pinches the cell into two equal parts, each part containing its own nucleus and cytoplasmic organelles.

Animal Cell

In plant cells a structure known as a cell plate forms midway between the divided nuclei. A cell wall forms between the two new cells. Plant Cell

Animation of Cell Division: apter2/animation__mitosis_and_cytokinesis.html apter2/animation__mitosis_and_cytokinesis.html

Consolidation: CELL CYCLE MATCHING ACTIVITY - Each group will receive an envelope - Put the notes and diagrams in the correct order - When you are done, put the cut-outs back in the envelope and return to the teacher EXIT CARD -Complete the exit card independently and submit before the end of class