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An introduction to microorganisms and the tools scientists use to see them.
Did you know that there are more living organisms on your hand right now than there are people on the entire planet?
Microbiology is the branch of science that explores organisms too small to be seen with the naked eye, known as microbes. This invisible world includes bacteria, viruses, fungi, and protists. While some microbes cause illness, most are helpful—they help us digest food, create oxygen, and recycle nutrients in the soil. Without these tiny powerhouses, life on Earth would simply stop.
Quick Check
What do we call the tiny organisms studied in microbiology that are invisible to the naked eye?
Answer
Microbes (or microorganisms).
If you are looking through a microscope with a eyepiece and a objective lens, what is the total magnification?
1. Identify the eyepiece power: 2. Identify the objective power: 3. Multiply them: 4. The object appears larger than its actual size.
Quick Check
If your microscope has a eyepiece and a objective, what is the total magnification?
Answer
Biologists divide all cells into two main groups. Prokaryotes (like bacteria) are simple and small. They are like a one-room studio apartment; their DNA just floats around because they have no nucleus. Eukaryotes (like plants, animals, and you!) are much larger and more complex. They are like a mansion with many rooms called organelles, including a dedicated nucleus that protects the cell's DNA.
Microbes are measured in micrometers ().
1. millimeter () = micrometers (). 2. A typical bacteria (prokaryote) is about to long. 3. A human cheek cell (eukaryote) is about wide. 4. This means you could fit about to bacteria across a single human cell!
Quick Check
Which cell type is more complex and contains a nucleus?
Answer
Eukaryotic cells.
Which of these is a characteristic of a Prokaryotic cell?
If a scientist uses a eyepiece and a oil-immersion objective, what is the total magnification?
Most microbes are harmful to humans and cause disease.
Review Tomorrow
In 24 hours, try to explain the difference between a 'studio apartment' cell and a 'mansion' cell to a friend without looking at your notes.
Practice Activity
Look at a strand of your hair. A human hair is about wide. Based on what you learned, how many bacteria could sit side-by-side across the width of that hair?