These worksheets look at the small organisms that are known for causing many diseases.

Often referred to as "germs" at a young age, we come to understand bacteria and viruses at a very young age. They are very small organisms and they are helpful as well as harmful. They help us digest foods and in the process make essential vitamins for us. There are only a handful of bacteria that cause us harm and some of them can help breakdown oil after large man made oil spills, helping other walks of life in the balance. There is also a running theory that bacteria produce half of the world’s oxygen. Viruses are many times smaller than bacteria. They are tiny parasites. Naturally they are harmful, but scientists are finding ways to use them to help patients in gene therapy and other health related applications. The volume of bacteria that inhabit the planet is sheerly overwhelming. If you were to collectively count them up, their biomass would far exceed all the plants and animals on Earth. If you were to take a one gram (the weight of a postage stamp) of soil and count the number of bacteria present, you would find close to forty-million bacterial cells. There are just under a half a million viruses that are known to infect mammals, but there are many different types of viruses that reside inside organisms from other kingdoms.

Students will get up close and personal with the anatomy of a virus and be able to identify key structures. We also spend a good bit of time on the anatomy of a bacterial cell, but that is more general. The last selection of the worksheet set examines all the different disease that are caused directly or indirectly in humans by a virus or bacterial infection. These worksheets look at the structure and function of viruses. They also look at structures within bacteria and how they reproduce. We also look at how certain bacteria cause disease.

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Print Bacteria and Virus Worksheets

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The Biology of Viruses

Identify the structure and function of parts on bacteriophages, a polyhedral virus, a rod-shaped virus.

The Anatomy and Reproductive Parts of Bacteria

A typical moneran is diagrammed below. Provide the labels for the parts and state the function or purpose of each structure.

The Cause of Diseases

What cause each type of disease that is listed?

Good or Bad?

We classify certain bacteria as "good" bacteria because they are an important part of our body's system. We actually can't live without them. For example, the bacteria in our digestive system, referred to as the gut microbiome, helps us to digest food and extract nutrients from it. It also plays a role in the functioning of our immune system.

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QUESTIONS: Good or Bad?

Yogurt, cheese, pickles, and soy sauce are all made using specific strains of bacteria which help to preserve food while giving it a unique flavor.

Are They Living?

Scientists disagree on whether or not viruses are themselves living things. Some argue that they are not living creatures because they don’t metabolize food into energy or have organized cells. They are also not generally able to reproduce outside of a host and are inactive when not inside a living cell.

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QUESTIONS: Are They Living?

Viruses are a kind of microorganism. They contain several strands of genetic material (DNA or RNA) and are surrounded by a layer of protein called the CAPSID. A virus does not have a nucleus.

Size, Shape, and Reproduction

They inject their DNA directly into their host's cells and begin to replicate.

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Question Set: Size, Shape, and Reproduction

We look at how they make plants and animals sick.

The Health Consequences

The toxins that bacteria produce fasten themselves to cellular structures and prevent the cell from working properly.

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Question Set: Health Consequences

We have used their method of incorporating viral DNA into host cells as a model for how to introduce beneficial genes into host cells.

Bacteria: Size, Shape, and Reproduction

First, the bacterium's DNA makes a copy of itself. The cell then grows longer and splits into two cells, each of which contain a strand of DNA identical to that of the parent cell. These daughter cells are actually clones of the original cell.

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Bacteria Question Set: Size, Shape, and Reproduction

At this rate, one bacterium can produce over two million copies of itself in just seven hours. Within another hour, it can have made a total of over 16 million copies.

The Gut Microbiome

Human gastrointestinal microbiota, also known as the gut microbiome, are the microorganisms that live in the digestive tracts of humans and many non-human animals, including insects.

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Questions: The Gut Microbiome

Beneficial bacteria in the gut normally keep the cells of the epithelium healthy by providing them with short-chain fatty acids and other nutrients that they need.

Antibiotic Resistance

Antibiotic resistance was first recognized in Japan after World War II with a type of dysentery that is a severe form of shigellosis.

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Antibiotic Resistance Question Series

Antibiotic resistant bacteria have evolved as the result of a combination of natural selection, as described by Charles Darwin, and a recently understood evolutionary mechanism called horizontal gene transfer.


When a disease can be spread from person to person, we say it is contagious. Contagious diseases can spread through contact with an infected person.

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Question Set: Contagion

Different contagious diseases have different incubation periods. This is the amount of time that a contagion needs to be in your body before it actually makes you sick.


While you will probably get the measles if you sit next to someone on a bus who has it, you can sit next to someone with Ebola and not necessarily get sick.

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Vaccines Questions

This "one and done" concept is what makes vaccines so effective. Vaccines work because they "teach" your immune system to recognize a particular kind of virus and to fight it off before it gets a chance to proliferate.

It's Alive or Not?

Living things have cells. Some living things, like bacteria, are cells. This is why we call them single-celled organisms.

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It's Alive or Not? Questions

Living things respond to their environment, and there is debate about whether or not viruses do this.