Bacteria vs. Protists

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  • 0:01 Introduction to…
  • 0:37 Characteristics of Bacteria
  • 2:01 Characteristics of Protists
  • 3:47 The Major Differences
  • 4:13 The Similarities
  • 4:36 Lesson Summary
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Lesson Transcript
Instructor: Danielle Haak

Danielle has a PhD in Natural Resource Sciences and a MSc in Biological Sciences

There can be a lot of confusion when it comes to differentiating among small organisms like bacteria and protists. This lesson will help you see how they differ and give examples of each!

Introduction to Bacteria & Protists

The world has more organisms than scientists have been able to count and classify. Identification can be tricky because so many organisms are microscopic in size and invisible to the naked eye. Two of the categories that often get confused with one another are bacteria, which are single-celled microbes, and protists, which are eukaryotic organisms that are not plants, fungi, or animals. Let's take a look at what makes each of these organisms unique more than just these simple definitions, and while we're at it, we can also see how they are similar.

Characteristics of Bacteria

What are bacteria? They are some of the oldest known organisms and are classified as prokaryotes. What does that mean? Well, prokaryotes are simple, single-celled organisms that lack organelles. If we look at bacteria, we see a single-celled organism with a flexible cell wall, a semi-permeable cell membrane, single-loop DNA, and enzymes. There are no internal compartments or structures, and no sexual reproduction takes place.

When bacteria multiply, it's usually through the process of asexual reproduction by binary fission. We may see colonies or groups of bacteria form, but each individual bacterium in that group is still a unicellular organism. Bacteria have three primary shapes: cocci (ball-shaped), bacilli (rod-shaped), and spirilla (spiral-shaped). Their differences are generally biochemical in nature, rather than physical. Some bacteria are helpful to humans, while others are harmful.

One type of bacteria you may be unknowingly familiar with is Staphylococcus aureus. These bacteria can cause digestive problems when consumed on contaminated food. The results are generally referred to as food poisoning. They're also the culprit of staph infections, which can be mild, like a pimple, or severe, like meningitis!

Characteristics of Protists

Now let's look at the group of organisms known as protists. These are small eukaryotes. A eukaroytic organism can be unicellular or multicellular; most (but not all) protists are actually unicellular. Unlike bacteria, protists have specialized organelles, including a true nucleus confined by a nuclear membrane. This compartmentalization differentiates protists from bacteria. You can think of prokaryotes (bacteria) that have no nucleus or organelles like an empty house, whereas eukaryotes (protists) are like a house full of appliances that have different functions. Both are still houses, one is just more complex than the other.

Additionally, protists are generally larger in size. Some protists ingest food, while others may make their own food. These photosynthetic protists, such as blue-green algae, contain chloroplasts, too. We can further classify protists based on their functions. There are animal-like protists (heterotrophs), fungal-like protists (decomposers), and plant-like protists (photosynthetic).

Animal-like protists are called protozoa. They are small, eat other organisms, and are capable of moving through the use of cilia or flagella. One animal-like protist you may be familiar with is the amoeba, which can be found in freshwater.

Plant-like protists are also known as algae, and most are capable of making their own food through photosynthesis. Volvox is a type of green algae commonly found in freshwater. Fungal-like protists include organisms that get their food by decomposing dead organisms; this group includes slime molds and water molds.

The Major Differences

We can sum up the major differences between bacteria and protists here:


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