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

Reproduction

Repair Cells divide to repair tissues upon injury Cells divide to replace old or damaged

cells When cell division goes wrong, cancer

can occur

Repair

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