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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).

Part 1: Equivalent fractions and the simplest form of a fraction
Part 2: Examples of equivalent fractions
Part 3: Common mistakes and misconceptions

Introduction to the cell.

In this online lesson you will learn how to compare measurements that have different units.

In this unit you will learn how to convert between common metric units of measure.

Part 1: Proper, improper and mixed fractions
Part 2: Examples of proper, improper and mixed fractions
Part 3: Common mistakes and misconceptions

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.

By the end of this unit you will be able to:

• Use a ruler and protractor accurately
• Understand the SI system of measurement
• Convert between different units