AIM: Why and how do cells divide.
DN: Compare and Contrast Sexual
and Asexual Reproduction.
HW: Castle Learning due Monday
Compare the size of these
organisms
Vs.
Vs.
Do these organisms have different
size cells?
No
How do
organisms
get so big?
Cell
Division
Why do cells divide rather than
grow in size?
XX
XX
XX
XX
XX
XX
XX
XX
+
XX
XX
DNA “Overload”
Small Town
DNA Library
Nucleus (DNA) loses
control over the
Cell as it grows larger!!
City
Exchange of Materials
Cell Membrane
4 small cells have more surface area
than 1 big cell
•More cell membrane – less cytoplasm
Surface
area
Rate of
Exchange
Increases
Surface Area
Small particles have a relatively larger surface
area than large particles.
Why?
What will melt first?
The smaller
chips have
more surface
area.
Vs.
Ice Cube
Ice Chips
Smaller cells have more
surface area and can
exchange materials across
membrane more efficiently.
What is Cell Division?
One cell divides into 2
new daughter cells
Size?
What happens to the chromosomes
before a cell divides?
They need to replicate
• What does replication mean?
• To make an exact copy of the
chromosome.
Chromosomes Replicate
before the cell divides
Centromere
2 Chromatids
1 Chromosome
When do cells divide?
Organism Growth
When do cells divide?
Repair
What tissues in our body need
to undergo a lot of cell division?
Skin
Bone
Stomach
Why?
What is Mitosis?
Mitosis is the process that divides
the cell’s nucleus into two, each
with a complete set of genetic
material from the parent’s cell
What are the phases of the Cell
Cycle?
Interphase
Centriole
Stages of Mitosis:
Prophase:
1)The chromosomes
becomevi sible.
2)The centrioles
separate and Spindle
fibers begin to form.
Centriole
Nuclear
Membrane
3)The nuclear membrane
Spindle Fibers breaks down.
Stages of Mitosis:
Metaphase:
1)The chromosomes line
up across the center of
the cell.
2)Each chromosome is
connected to a spindle
fiber at the centromere.
Stages of Mitosis:
Anaphase:
1)The spindle
fibers separate
the chromatids
into individual
chromosomes and
are they
are moved apart.
Stages of Mitosis:
Telophase:
1)The chromosomes gather at
opposite
ends of the cell.
2) Two new nuclear membranes
form.
3)The chromosomes lose their distinct
shapes.
Cytokinesis:
The cytoplasm pinches
and two cells are formed.
What is the end result of Mitosis?
46X
Parent
+
46X
Daughter Cell
Chromosome Number?
The same number of
chromosomes is maintained
from one generation to the
next.
46X
Daughter Cell
Is the genetic material of the
daughter cells identical to the
parent?
YES
Mitosis Phases
Prophase Metaphase
Cytokinesis
Anaphase
Telophase
Plant Cells vs. Animal Cells
Which are plant cells and which are animal cells?
Animal Cells
Cell Wall
Plant Cells
Plant Cell vs. Animal Cell Mitosis
How is plant cytokinesis different
than animal cell cytokinesis?
In an animal cell, the
cytoplasm pinches off.
What process is this?
Cytokinesis
In plants, a Cell Plate forms
across the middle of the
cell.
Which phase are these cells in?
Prophase
Anaphase
What phase are these cells in?
Telophase
Metaphase