Prokaryotes & Eukaryotes: Definition & Examples

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Adrianne Baron

Adrianne has a master's degree in cancer biology and has taught high school and college biology.

Expert Contributor
Amanda Robb

Amanda has taught high school science for over 10 years. She has a Master's Degree in Cellular and Molecular Physiology from Tufts Medical School and a Master's of Teaching from Simmons College. She is also certified in secondary special education, biology, and physics in Massachusetts.

Living organisms are defined as being either a prokaryote or a eukaryote. Learn how to compare and contrast examples of prokaryotes, which are one-cell organisms without a nucleus, with eukaryotes, which include humans, animals, and most anything living thing visible to the naked eye. Updated: 09/30/2021

Prokaryote or Eukaryote?

Have you or anyone you know ever had strep throat before? If so, then you, a eukaryote, have become acquainted with a prokaryote. Now, you are probably asking several questions at this point. What in the world is a eukaryote? What is a prokaryote? How am I a eukaryote? Which prokaryote did I get to know? Well, let's get you the answers to your questions.

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  • 0:00 Prokaryote or Eukaryote?
  • 0:25 Prokaryotes
  • 1:10 Examples of Prokaryotes
  • 3:45 Eukaryotes
  • 4:25 Examples of Eukaryotes
  • 5:35 Lesson Summary
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Prokaryotes are 1-celled organisms that do not have a nucleus or any other membrane-bound organelles inside them. The name prokaryote itself actually lets you know that there isn't a nucleus, since pro means before and karyo refers to nucleus.

Prokaryotes are filled with cytoplasm and contain very few and basic internal structures. The genetic information is carried on circular pieces of DNA. There may be only one piece of DNA or many pieces of DNA. The only organelles, or internal structures that exist in prokaryotes are ribosomes, which make proteins needed by the organism. Prokaryotes include Archaea, bacteria and cyanobacteria. That answers the question about what a prokaryote is.

Examples of Prokaryotes

So, now let's address the question about which prokaryote you became familiar with during that case of strep throat. Strep throat is caused by a Group A strep bacterium called streptococcus pyogenes. 'S. pyogenes are gram-positive and do not move on their own. This bacterium causes strep throat and can also cause impetigo, scarlet fever and cellulitis - and a few other diseases in our bodies.

While this may not have been such a happy meeting with this prokaryote, these bacteria are able to live in our bodies and not cause any disease at all. As a matter of fact, there are many bacteria that are helpful in our bodies. Let's discuss one now.

It would be very difficult to break down the foods we eat without the help of bacteria. One bacterium that helps to break down food is lactobacillus acidophilus. L. acidophilus reside naturally in our gastrointestinal tract. These bacteria like to grow in very acidic areas and convert the sugar lactose into lactic acid. This action is what allows us to enjoy dairy products, such as that melted cheese on a slice of pizza. Yum!

Let's also talk about the prokaryote cyanobacteria mentioned earlier.


Cyanobacteria are unique in many ways. These are considered to be the oldest living organisms on the Earth and are the most abundant of the prokaryotes. They are able to make their own food through photosynthesis, and through that process, they have released a lot of the oxygen we breathe. Cyanobacteria live in water and are often found living together in clumps known as colonies. Cyanobacteria are often used in fertilizer to help with the growth of different crops. So, while there are some prokaryotes that can be harmful, there are many that are very useful and necessary for us to survive.

Finally, when talking about prokaryotes, we can't forget about the domain archaea. Although they were once classified as bacteria, these single-celled microorganisms make up their own domain. While many species of archaea are similar in size and shape to bacteria, they possess a different genetic structure and biochemistry. They were first thought of as extremophiles because they were found in harsh environments, such as volcanic vents and the Dead Sea. We know today, though, that archaea can inhabit a wide range of environments and are particularly abundant in the oceans.


Eukaryotes developed many years after prokaryotes and are substantially more complex. Their name also tells you about the nucleus, since eu- means 'true,' and we know already that karyo- means 'nucleus.'

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Additional Activities

Compare and Contrast

In this activity, students will be creating a colorful and attractive poster that utilizes a Venn diagram. A Venn diagram is a chart used to compare the similarities and differences between two ideas. To create a Venn diagram, students draw two circles that overlap, creating an area to list the similarities between the two ideas. For example, a student might write that prokaryotes don't have a nucleus, but eukaryotes do. In the shared column they might write that both are cells, because this is a shared trait between prokaryotes and eukaryotes. If students are having trouble coming up with examples of prokaryotes and eukaryotes they can use the internet for additional research.


Prokaryotes and eukaryotes are the two main types of cells that you learned about in this lesson. To practice what you learned, you'll be creating a Venn diagram poster in this activity to compare and contrast prokaryotes and eukaryotes. Your Venn diagram should include two circles that overlap. One circle is for information about prokaryotes and the other is for information about eukaryotes. The information in the middle is the characteristics they share. Use the checklist below to make sure your Venn diagram poster is successful.

Criteria for Success

  • A large Venn diagram comparing and contrasting prokaryotes and eukaryotes is the center of the poster
  • There are at least three details included for each section in the diagram
  • There are three examples of prokaryotes and eukaryotes with pictures included on the poster
  • The poster is colorful and attractive and easy to read

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