Study Guide:
Test Date: ________
Know these facts about protists.
1. Protists are mostly single-celled, eukaryotic organisms. Some are multi-cellular. Some
are autotrophs; some are heterotrophs; some are both. (Eukaryotic means having a
nucleus.)
2. In addition to a nucleus, protist cells have other organelles.
3. Kingdom Protista is know as the “junk drawer” or “odds and ends” kingdom. Organisms
as different as single-celled algae and 100 foot tall kelp “seaweed” belong to this
kingdom.
4. Some protists act like animals. The are heterotrophs and ingest their food. These
animal-like protists are called protozoans. Protozoans are all single-celled.
5. Some protists act like plants. They are autotrophs and make their food. These plant-like
protists are called algae. Some algae are single-celled like diatoms and Chlorella. Some
are multi-cellular but still microscopic like Volvox. Some are filamentous like Spirogyra.
Some are multi-cellular and can be easily seen with the unaided eye. These are called sea
weed. There are three main groups of seaweed: green, red, and golden/brown.)
6. Eutrophication is the build up of nutrients in a fresh water pond or lake caused by
seasonal overturn, fertilizer, or sewage. Excess nitrogen causes an out-of-control algae
growth. The algae that covers the surface of the water prevents sunlight from reaching
other algae and plants living below the surface. These organisms die and fall to the
bottom of the pond. Bacteria eat the dead organisms and use up the oxygen in the water.
Organisms that depend on the oxygen in the water die.
7. Some protists act like fungi and go through a complicated life cycle at one point moving
like animals. There are know as the slime molds. Other fungus-like protists are the water
molds and downy molds.
8. Supplementary Information: Many scientists think that protists developed from bacterialike organisms that were “invaded” by other smaller bacteria-like organisms. These
invaders developed a mutually beneficial relationship with their hosts. And so, it worked
out that the invaders become incorporated into their host organisms. The host helped the
invader by providing it with a home. The invader helped the host by making its food or
providing it with energy. (When one microscopic organism comes to live within another
microorganism the process is known as endosymbiosis. This process may explain the
existence of chloroplasts and mitochondria, both of which have their own genetic
material. This indicates that these two organelles may have been “free-living” at one
time.
9. Scientists have had problems classifying protists because they are all so different.
10. Kingdom Protista is divided into many phyla or groups.
11. There are four main groups of animal-like protists.
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a. Sarcodines: irregular, blob-shaped protozoans. They move by extending
their cell membrane and cytoplasm to form pseudopods (false feet). An
Amoeba is an example of a sarcodine. Sarcodines also use their pseudopods
to surround (engulf) their food.
b. Ciliates: move using cilia, tiny hair-like structures that sweep them along
and help them direct food into their mouths. An example of a ciliate is a
Paramecium.
c. Zooflagellates. move using whip-like tails called flagella. An example of a
zooflagellae is Giardia which infects steams and ponds and causes “Hiker’s
Diarrhea.
d. Sporozoans: live inside other organisms as parasites. A sporozoan called
Plasmodium causes malaria.
12. There are six main groups of plant-like protists. All are autotrophs and can make their
own food like plants.
a. Flagellates: move using whip-like tails called flagella. Euglena is an
example of a flagellate. Euglena has an eyespot to detect light. When light is
available, Euglena can make its own food through photosynthesis. When light
is not available, Euglena ingest nutrients from its environment.
b. Diatoms: have glass-like shells made of silica. (This is an ingredient in pastes
and polishes.)
c. Dinoflagellates: have outer coverings that look like armor. They also have
flagella for moving. Red tide is the rapid reproduction of dinoflagellates
which produce toxins that kill fish and other marine organisms. Red tide
is caused by excess nutrients in salt water from run-off that contains fertilizer,
sewage, and factory wastes.
d. Green Algae: range from the microscopic Chlorella to the colonial Volvox to
the macroscopic Ulva (sea lettuce). Sea lettuce is rich in beta-carotene which
is added to food as a supplemental nutrient. Beta-carotene is rich in
ingredients that may fight cancer and other conditions.
e. Red Algae: lives in deeper water because red pigment can promote
photosynthesis in dim light. The red algae, Chondrus crispus (Irish Moss) is
used to make ice cream and chocolate milk products smooth. Irish moss is
listed as the ingredient carageenan on packages of these foods.
f. Brown Algae: is used as a stabilizer in foods like salad dressing and gravies.
The ingredient is alginate. A common brown alga is rockweed (Fucus).
13. Three groups of fungus-like protists are heterotrophs.
a. Slime Molds: begin life as spores that develop into either amoeba-like
cells or flagellated cells. When food is not available, many of these singlecelled organisms aggregate to form a creeping mass that sometimes looks
like dog vomit. The mass is called a plasmodium. The cells in the plasmodium
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push into the center of the mass and form towers that have spore cases
on the top. These are called fruiting bodies or sporangia. When the spores
are released, the whole cycle begins again.
b. Water molds form fuzzy growths on other living organisms. The Great
Potato Famine in Ireland in 1845-46 was caused by a water mold. Now known
as the Irish Genocide, the famine caused the death of 1/3 of Ireland’s
population in those years.
c. Downy Molds attach plants like cabbage and corn leaving unsightly spots on
their leaves.
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