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Introduction to cell theory--the idea that 1) all living things are made of one or more cells, 2) cells are the basic unit of life and 3) all cells come from other cells. Explore the roles that Hooke, Leeuwenhoek and others played in developing cell theory.

Hooke and Leeuwenhoek were two of the first scientists to use microscopes to study the microscopic world of cells. Hooke coined the term "cell" after observing the tiny compartments in cork, while Leeuwenhoek discovered a variety of living creatures in pond water, blood, and other samples. They contributed to the cell theory by suggesting that cells are the fundamental units of life and structure, and that all living things consist of one or more cells that originate from other cells by division. 

All living things are made up of cells, which is the smallest unit that can be said to be alive. An organism may consist of one single cell (unicellular) or many different numbers and types of cells (multicellular).

The amount of effort saved when using machines is called mechanical advantage (MA). Simple machines use mechanical advantage as a key property to their functionality, helping humans perform tasks that would require more force than a person could produce. We will use the lever as an example of a simple machine to illustrate the concept of mechanical advantage.

Introduction to the cell.

In this unit we will learn how these factors can affect the output of a simple machine. We will also learn about the difference between ideal mechanical advantage (IMA) and actual mechanical advantage (AMA), and how to apply your knowledge to calculate the efficiency of various simple machines.

Even though molecules, proteins, viruses, and cells are all tiny, there are significant size differences between them. The diameter of a water molecule is roughly 0.28 nanometers. The diameter of the protein hemoglobin is roughly 5 nanometers. The diameter of the HIV virus is roughly 120 nanometers. A red blood cell is 6-8 micrometers.

What are simple machines? Simple machines are tools that make work easier. They have few or no moving parts. These machines use energy to do work with one movement. They make our work easier by letting us use less mechanical effort to move an object.

This YouTube video investigates the structure and composition of the sun.

These four short online lessons cover the following:

• What is the sun?
• Interior of the sun
• Outer layers of the sun
• Surface features of the sun

This online resource investigates the internal structure, outer layers and surface features of the sun.