Deep in the woods lies a peaceful pond. The surface is calm, undisturbed by the fish swimming
beneath the surface. The croak of a frog joins a chorus of birds echoing through the surrounding
trees. During the day, this pond might be visited by different animals looking for a drink or even
beavers looking for a place to build their lodge. Ponds are a happy habitat for lots of creatures,
many of which are too small for us to see. If we scooped up a cup of water from this pond,
what do you think we would see? It might just appear to be a simple cup of water, but within the
pond water, invisible to our eyes, are thousands of microorganisms. Some of these organisms,
which are in the kingdom Protista, are eukaryotic creatures known as protozoans. The root of the
word protozoan is zoo, which means animal, but they are not classified as an animal,
a plant, or even a fungus. Protozoans do, however, share some characteristics with these groups.
Let's take a look at three different types of protists under a microscope.
This blob-like creature is an amoeba. It uses pseudopods or false feet to move itself around
its aquatic environment. When it comes in contact with another microscopic creature,
it will wrap its body around the creature engulfing and then eating it. An amoeba is an
animal-like protist or protozoan. Similar to animals, amoebas and other protozoans are able to
move but are not able to make their own food. Another protozoan is the paramecium.
These creatures have special hair-like appendages called cilia which flutter to help them move.
These are the most complex of all protozoa and can be found in freshwater or salt water.
The next creature is a flagellate.
These protozoans move with the help of whip-like structures or tails called flagella.
Many flagellates are parasitic and live in the bodies of other organisms. Several
types of protozoans, including flagellates, can cause sickness in humans if ingested.
Let's leave behind the animal-like protozoans and turn our attention to a different type of protist.
Do you see how this protist is green and has a different structure? This green algae protist
has more similarities to plants than animals. Like plants, it contains chlorophyll and can
photosynthesize to produce its own food. Have you ever seen the green scum that forms on the tops
of ponds? That scum is formed by many millions of these tiny microorganisms. The seaweed used
to roll up sushi is also a type of algae. This algae is green, but it can also be brown or red.
Let's take a moment to look at protists in a much larger body of water, the ocean. Brown algae is
the largest and most complex algae and includes kelp and sea palms. Vast underwater forests of
kelp anchor to the seafloor and grow up toward the light. Some have grown more than 60 meters tall.
They are often mistakenly considered plants, but in fact, are multicellular protists. These kelp
forests provide a habitat and food source for many ocean creatures. The last type of protists we will
explore are similar to fungi. These include slime molds, water molds, and downy mildew.
Slime molds can be red, orange, or bright yellow in color. They live in
moist environments and feed on decaying organisms. Water molds typically grow on decomposing algae
and freshwater animals. They can look like white, cottony fluff growing on the animals. Some water
molds live as parasites, invading the living organisms and using them as a source of food.
Downy mildew is a type of water mold but can actually live on land and can harm
plants. This unfortunate protist caused the Irish potato famine in the 1840s.
Protists are actually the culprits in several human diseases such as giardia, dysentery,
and malaria. But others play an important and positive role in the world's ecosystems.
Some protists feed on bad bacteria and help clean our water sources. They are also excellent
decomposers, helping to recycle nutrients through the environment. Alistair Simpson,
a professor at Dalhousie University, said, "If you took all the protists out of the world,
the ecosystem would collapse really quickly." God placed every living thing in its proper order
and every living thing has a function to play in the world He created."
Let's go back to our quiet pond in the forest. Now it's easy to see some of the bigger organisms in
this ecosystem, the lovely trees, bushes, and plants. And we can easily imagine the
animals that inhabit such a location. However, these life forms, as beautiful as they are,
make up only a small fraction of the organisms that call this pond home.
Beneath the tranquil surface dwells a thriving microscopic community of busy protists.