cell division 8 th grade science. let’s review cells! what do you know and remember about cells? ...
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Cell Division
8th Grade Science
Let’s Review Cells!
What do you know and remember about cells?
What are cells?
What is their function?
Cell Cell theory Prokaryote Eukaryote Organelle
What’s different about a cell and an atom? Cell- basic unit of life.
You can’t be considered alive if you are not composed of cells.
Atoms – basic unit of matter, smallest part of an element
Atoms & Cells are two very different things.
What is The Cell Theory?
1. All living things are made up of cells.
2. Cells are the basic units of structure and function in living things.
3. New cells are produced from existing cells.
Remember these?
What does the Nucleus do?
Contains DNA.- DNA: contains the hereditary information.
Controls most cell processes.- Makes proteins…the building blocks of almost everything.
What actually contains the DNA?
Chromatin- Consists of DNA
bound to protein. Usually spread
throughout the nucleus, but during cell division it condenses to form…
Chromosomes- Contain
hereditary genetic information.
How do little elephants grow up to be BIG elephants?
Why do animals shed their skin?
Cell division In multicellular
organisms cell division is needed for three things: Growth Reproduction Repair
Growth Efficiency of moving materials into the
cell The larger the cell becomes the less
efficient it is The volume of the cell increases faster
then its surface area Cells that grow too large no longer have
enough surface area to take in nutrients and remove waste
Growth
© Pearson Education, Inc.
Cell Size
Surface Area(length x width x 6)
Volume(length x width x height)
Ratio of Surface Areato Volume
1 cm x 1 cm x 6= 6 cm2
2 cm x 2 cm x 6= 24 cm2
3 cm x 3 cm x 6 = 54 cm2
1 cm x 1 cm x 1 cm= 1 cm3
2 cm x 2 cm x 2 cm= 8 cm3
3 cm x 3 cm x 3 cm = 27 cm3
6 / 1 = 6 : 1 24 / 8 = 3 : 1 54 / 27 = 2 : 1
Reproduction Cells divide in order to reproduce
themselves. All cells come from preexisting cells. Most cells divide by mitosis = making
exact copies of themselves Sex cells divide by meiosis = making
copies with ½ the genetic information
Repair Cells divide to repair tissues upon injury Cells divide to replace old or damaged
cells When cell division goes wrong, cancer
can occur
First, before a cell can split…
It must copy it’s genetic information.
Each daughter cell then gets a complete copy of that information.
How is genetic info passed on?
o Chromosomes carry the cells coded genetic information.o Made up of DNA and
proteins. Human cells have
46 chromosomes. 23 pairs.
Organisms can have different #’s of chromosomes.
Before cell division…
• Each chromosome is replicated (copied).
• Each chromosome consists of two identical “sister chromatids.”
• Attached at the center by a centromere.
Mitosis Cyclehttp://www.cellsalive.com/mitosis.htm
• Interphase
• Prophase
• Metaphase
• Anaphase
• Telophase & Cytokinesis
Animated Mitosis Cycle
• Cell division occurs in a series of stages, or phases.
http://www.cellsalive.com/mitosis.htm
Mitosis Review
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis