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 6.3072 x 1013
• Huh? That’s
630 720 000 000 000 000
red blood cells in one year.
Why do cells divide?
Cell Division for Growth
2. Cell Division for Repair
1.
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.
2.
3.
4.
Prophase
Metaphase
Anaphase
Telophase
(P)
(M)
(A)
(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:
• http://highered.mheducation.com/sites/0072495855/student_view0/ch
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