Intro+to+Cells

media type="youtube" key="QbVNVOJP3q0" height="390" width="480" Cells are related to tissues the same way organs are related to organ systems. Organisms are created from a group of organ systems, and there are two types of organisms. Unicellular and Multicellular. Unicellular organisms are single cells living on its own. Multicellular organisms can only exist as a group of cells. Then popluation is created from organisms, the community from poplulation, and ecosystem. These cells are grouped by the order below:

cell- tissue- organ - organ system - organism - population - community - ecosystem -

These cells are grouped from the least to greatest.

Cells were descovered when Robert Hooke desided to look at a thin slice of cork, and the cork looked like hundreds of little boxes, so he named these boxes "cells" which means "little rooms" in Latin.

Over the years the cell theories were created. The cell theories are: -All organisms are made of cells. -The cell is the basic unit of life.

-All cells come from existing cells.

There are two types of cells. Prokaryotic cells and Eukaryotic cells.

Prokaryotic cells have:
 * Circular DNA.
 * Smallest cells of all.
 * They contain cell wall.
 * They are the simplest cells.
 * They don't have nucleus.

All cells have in common. They are:
 * Cell mebrane
 * DNA
 * Cytoplasm
 * Organelles
 * Too small to be seen with the nake eyes.

Eukaryotic cells have:
 * Linear DNA
 * Some Eukaryotic cells don't have cell walls
 * Eukaryotic cells have two types. Animal cells and plant cells.
 * Have nucleus.
 * Complex
 * Contains many complex cells.

The surface-to-volumn ratio is a comparison of the cell's outer surface to the cell's volumn. The volumn of the ratio decreases as the cells get bigger.

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