Download Getting to Know: Protists

Getting to Know: Protists
You probably know about plants, animals,
and fungi, but how much do you really know
about protists?
Protists are a very diverse group of
organisms classified in the Kingdom Protista.
Many protists are single-celled, but some,
like algae, are multicellular. Protist cells are
eukaryotic, like the ones that make up your
body and the bodies of all other plants and
animals. Like all eukaryotic cells, protist cells
have specialized parts, called organelles,
which perform life functions. Examples of
organelles include mitochondria, which
break down sugar for energy, and ribosomes,
which assemble proteins. The DNA of
protists is arranged in chromosomes and
contained inside a nucleus. Protists have
a great variety of shapes and specialized
structures that help them adapt to many
environments and niches.
Naturalist Rev. J. G. Wood published this
wood engraving of protists in 1882. The word
“animalcules” means “microscopic animals.”
The classification of protists has changed over
the years as scientists have learned more
about them.
Misconception 1: Single-celled organisms are very simple. They are little more
than tiny spheres with some genetic material inside.
When many people think of single-celled organisms, they think of bacteria, which
are very simple prokaryotic cells. Bacteria are basically just a membrane and genetic
material. On the other hand, protists are eukaryotic. They are relatively large, complex
cells with a great variety of specialized forms and functions. It is truly amazing how
complex single-celled protists can be. In fact, some protists such as Volvox exist in
complex, multicellular colonies.
Concept: Protists
Getting to Know
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Misconception 2: All protists are harmful pathogens that spread disease.
There are some dangerous protists that cause disease. However, most protists are not
pathogens. In fact, protists provide many benefits to life on Earth. For example, protists
are at the base of many marine food chains. Without these protists, many kinds of
seafood would not exist.
Are protists like tiny animals or plants?
Many protists have some characteristics of plants
and some characteristics of animals. That’s why
scientists ended up classifying them in their own
kingdom.
Protists are very diverse in their methods of
obtaining energy. Some are like tiny animals,
eating smaller organisms for food. Others are like
tiny plants and have chloroplasts to make their
own food by photosynthesis. Some are like fungi,
breaking down dead organic matter. Some can
even do all three!
Where do protists live?
These single-celled Euglena have
characteristics of both plants and animals.
Like plants, they have chloroplasts and
can perform photosynthesis. Like animals,
they lack a cell wall, have an eyespot that
detects light, and can move from place to
place.
All protists are aquatic, which means they must
live in water all the time. Protists live in a wide
variety of aquatic environments, including
freshwater and saltwater biomes. They are
commonly found in ponds, rivers, lakes, and
oceans.
Now that you have been introduced to protists, get ready to learn more exciting details about
these interesting organisms!
Misconception 3: All protists perform photosynthesis and are found in the ocean.
Many people are familiar with phytoplankton. These important protists make up the
base of the marine food chain. However, phytoplankton make up only one group of
protists. There are many thousands of protist species. Many species do not perform
photosynthesis and must obtain energy by eating other organisms.
Concept: Protists
Getting to Know
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© Discovery Education. All rights reserved.
Discovery Education is a subsidiary
of Discovery Communications, LLC.