In this video lesson, you will learn how some one-celled organisms can be beneficial to other larger organisms. You will see how some of these one-celled organisms actually provide food for the larger organism.
In this lesson, we talk about protists. The protists are one-celled organisms.
Protists can live by themselves or in colonies. Protozoa, some algae, and slime molds are some examples of protists. The protists that we see are usually the protists that live in colonies.
When they live on their own, they’re usually too small to see with our naked eye. Some protists are beneficial, while others do harm. In this lesson, we’ll discuss some of the protists that do good.
We’ll begin with symbiotic protists.
These are protists that live with other larger organisms in a mutually beneficial relationship. Symbiotic means that both parties benefit from each other; both the protists and the larger organism benefit from this arrangement. Many times, it is the larger organism providing protection for the protists, and the protists providing an essential service to the larger organism.
The anaerobic parabasalid species of protist is an example of this type of protist. This species of protist happens to live in the digestive tract of wood-eating cockroaches and termites. The termite or the cockroach and the protists form a symbiotic relationship, where the protists help the insect digest the wood that it eats, and the termite or cockroach provides the shelter and protection to the protists.
Without these protists, the termites and cockroaches wouldn’t be able to eat, and without the termites and cockroaches, the protists wouldn’t have protection; they need each other.
Another beneficial type of potists are the photosynthetic protists. These are protists that process sunlight. Algae and diatoms are common photosynthetic protists. They are very common in the world’s oceans, where they are actually responsible for 80% of the world’s photosynthetic processes. That’s right: all of our land plants and trees combined don’t produce as much oxygen as these photosynthetic protists do.
The dinoflagellates Noctiluca and Pyrocystis are very interesting examples of this type of protist. These protists live on the surface of water bodies such as our oceans. They process sunlight and they also glow in the dark. They contain what are called photo-phosphorescent granules. When you go out in the ocean in the middle of the night, you will at times see the surface of the ocean glowing in the darkness from these protists.
This last type of protist that we will talk about are the protists that serve a dual purpose.
These protists are both symbiotic and photosynthetic. Many of these live with another, larger organism. The larger organism gives the protists protection and a place to live. The protists, in exchange, photosynthesize sunlight and turn it into food for the larger organism, or some other useful form that allows the larger organism to thrive.
The protists zooxanthellae are examples of these types of protists. These protists live inside coral. They provide the coral with the carbon that the coral needs to continue growing. The coral provides the protists with the ideal environment in which to do their photosynthetic work. If the coral didn’t have these protists with them, they would first lose their color and turn white.
Then, the coral would eventually die.
Let’s review what we’ve learned. Protists are one-celled organisms.
Symbiotic protists are protists that live with other larger organisms in a mutually beneficial relationship. The anaerobic parabasalid species of protist is an example. Photosynthetic protists are the protists that process sunlight. The dinoflagellates Noctiluca and Pyrocystis are examples of this type of protist. There are also protists that serve both purposes: they are both symbiotic and photosynthetic.
The protists zooxanthellae are an example of this type of protist.