Cell Growth Do Now: Do organisms get larger when they grow because each cell increases in size or because it produces more of them?

I. Why should cells divide? A. DNA overload 1.There is only one original copy of DNA in each cell 2. If the cell gets too big, the DNA can not serve it. 3. A small library can only serve a small town. More people = the library needs more books

B. Exchanging Materials 1. Food, O 2, H 2 O into a cell, CO 2 and waste out through the cell membrane 2. If the cell is too big, not enough nutrients will be moved in and too much waste will build up. 3. There would not be enough surface area for the increasing volume

II. Surface Area to Volume A. Volume increases more rapidly than the surface area. Surface area = (length x width)(number of sides) Volume = length x width x height Surface area/volume = ratio

Figure it out…

III. Cell Division A. Before the cell becomes too large: 1. It copies (replicates) it’s DNA 2. Divides into 2 equal and identical daughter cells

10-2 Cell Division

That first cell had all the information and instructions to make you as you are now. It was all in a secret code in the middle of the cell. This code is called DNA. It is a very long list of instructions that gives each cell in your body its own shape and function.

That first cell grew a little and then "wiggly" bits called chromosomes could clearly be seen. Half of the chromosomes came from the egg cell, and half from the sperm cell and each chromosome contained two copies of that secret code, the plans to make you That first cell grew a little and then "wiggly" bits called chromosomes could clearly be seen. Half of the chromosomes came from the egg cell, and half from the sperm cell and each chromosome contained two copies of that secret code, the plans to make yousecret codesecret code The first cell then divided into two separate cells using a process called cell division and this is how it happened... The first cell then divided into two separate cells using a process called cell division and this is how it happened...

First the chromosomes lined up in the center of the cell. First the chromosomes lined up in the center of the cell.

Then each chromosome split into two identical halves.

Next the cell made a fold down its middle and...

HEY PRESTO!!! Two cells, which both had all the information and instructions to make you...and then...

Those cells grew a bit... copied their chromosomes and those became then became then became then then Those cells grew a bit... copied their chromosomes and those became then became then became then then then then

Then: You get the idea…

Very soon there were

If one of your cells was really this size you'd be as big as the Empire State Building in America. Empire State BuildingEmpire State Building

I. Chromosomes A. Made of DNA and proteins B. Invisible except during cell division (chromatin  chromosomes) C. Human cells have 46 carrot cells have 18

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