Cell Theory

​Can our cells do all of these things?

​Scientists agree that all living things are composed of cells. From the most minuscule bacterium to the largest blue whale, every living thing on Earth contains cells. Cells are the basic unit of structure and function in living things.

​Theories, Laws, and Hypotheses

​Video

What happened in each of these pictures?

Wind blew the pot over through an open window.

It didn't rain, the landscaper was watering plants.

The dog jumped into the window. Timmy didn't break it with the baseball.

Unlike our theories on the past slides, a scientific theory is not a guess — it’s one of the strongest, most well-tested ideas in science.

​What is the difference between a scientific theory and a scientific law?

TED-Ed: The Wacky History of Cell Theory

​What are the 3 parts of the cell theory?

YOU WILL NEED TO KNOW THIS!

1. All Living Things Are Composed of Cells

   
   

Recall that all living things are made of cells. This statement is both a characteristic of life and one of the statements of cell theory. Some organisms are unicellular, and some are multicellular. However, every organism ever discovered is composed of one or more cells. Scientists have never discovered a living thing that did not contain cells.

2. Cells Are the Basic Unit of Structure and Function in Living Things
   
   

Organisms are systems. Cells are the smallest living unit of an organism. Cells contain even smaller structures called organelles. An organelle is a structure within a cell that performs a specific function. Organelles are like tiny cell organs. Many organelles form a living cell, even though each individual organelle is not alive.

3. All Cells Come From Other Cells
   
   

Every cell on Earth is descended from another cell. Cells reproduce by dividing in half. Your body makes new cells by dividing the cells that already exist. The egg that hatches into a chick and the acorn that grows into a tree begin as single cells. Every living thing is the product of another cell.