Transcript 7th chapter 3 lesson 1

Paramecium
From a cell to an
organism
Chapter 3 lesson 1
Life Science
Presented by
Mrs. Waterbury
Section 3-1 Cell Cycle
and Cell Division
Length of cell cycle
depends on the cell
skin – 15-20 days
nerve – 50-60 yrs
Growth = cell number
increases
Division
development
Ex. Red blood cells – 2 to 3
billion per second
Interphase – Cell Cycle
phase 1 (9/10 of life)
1) rapid growth and replication of organelles;
cellular functions –ex making protein; stomach
cells making enzymes G1 (some cells stop here
ex brain cells)
2) Growth & DNA replication S
chromatin (what chromosomes are called
during interphase) doubling; sister chromatids
held together by a centromere make up 1
duplicated chromosome see pg 88 pict
3) preparation for division; store energy; growth;
organelle replication G2
4) Mitosis cell cycle phase 2 (cell
division (nuclear division) stage1
) (1/10) (average
time – 24 hrs)
INTERPHASE
Interphase looks like spaghetti
STAGES:
1) Prophase
Chromosomes visible by
coiling together tightly
Nuclear membrane breaks
down
Nucleolus disappears
Centrioles (animals only)
move to opp. Ends
Spindle Fibers begin to
stretch across
PROPHASE
2) Metaphase
Chromosomes
line up in the
center pushed
by the fibers
Attach to a fiber
by the
centromere
Shortest phase
3) Anaphase
Centromere divide
these are the
structures that hold the
double stranded
chromosome together
Chromosomes (sister
chromatids) separate
Strands start to move
toward opposite ends
centromere Cell begins to lengthen
http://www.unomaha.edu/~swick/
2740mitosis.html
http://www.bioweb.uncc.edu/biol1
110/Stages.htm
4) Telophase
Nuclear membrane forms
around each mass of
chromosomes
Two new identical nuclei are
formed
New nucleolus appears
Animals – cytoplasm divides
(cytokinesis – cell division
stage 2) forms a furrow
Plants – cell plate forms
(cytokinesis) Why?
A new cell has formed that is
identical to the parent cell
(daughter cells
Will have the same number
of chromosomes!
Results of cell division
How some unicellular organisms
reproduce (paramecium)
Growth
Replacement – worn out or damaged
ex skin
Repair – broken bones, cuts (not all
can be repaired – ex nerves