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PROTISTS ‘R US
What is a Protist?
Protists are organisms that are classified into the kingdom Protista. The protists form a group of organisms that really do not fit into
any other kingdom. Although there is a lot of variety within the protists, they do share some common characteristics. All protists are
eukaryotic. That is, all protists have cells with nuclei. In addition, all protists live in moist environments. Protists can be unicellular
or multicellular. Protists can be microscopic or can be over 100 meters (300 feet) long. Some protists are heterotrophs, while others
are autotrophs. Since protists vary so much, we will group them into three subcategories: animal-like protists, fungus-like protists, and
plant-like protists.
Protist #1 : The Euglena
Euglena is a common group of freshwater single celled
organisms in the Kingdom Protista. Euglena confused
early scientists because it is green like a plant and thus
carries out photosynthesis. However Euglena moves,
something that in the mind of the average person is
associated with animals, not plants. Also, unlike plants
Euglena does not have a cellulose cell wall. This is
what a typical Euglena looks like, The green oval
structures are the chloroplasts where photosynthesis
takes place. Notice the long whip-like structure on the
right side of the organism. That is a flagellum which
moves the Euglena through the water. One really cool
feature of Euglena is the presence of a photoreceptor
organelle, or eyespot, that allows the organism to orient
toward or away from light. This is a sensible adaptation
since these organisms carry out photosynthesis.
Protist #2 : The Amoeba
The amoeba is a one-celled organism. Amoebas live
in fresh water (like puddle and ponds), in salt water,
in wet soil, and in animals (including people). There
are many different types of amoebas. An amoeba
consists of a single blobby cell surrounded by a
porous cell membrane. The amoeba "breathes" using
this membrane - oxygen gas from the water passes in
to the amoeba through the cell membrane and carbon
dioxide gas leaves through it. Amoebas eat algae,
bacteria, plant cells, and microscopic protozoa and
metazoa - some amoebas are parasites. They eat by
surrounding tiny particles of food with pseudopods,
forming a bubble-like food vacuole which also can
help with movement. The food vacuole digests the
food. Amoebas move by changing the shape of their
body, forming pseudopods (temporary foot-like
structures). The word pseudopod means "false foot."
Amoebas reproduce by binary fission. A parent cell
divides (the nucleus also divides in a process called
fission) and produces two smaller copies of itself.
Protist #3 : The Paramecium
The paramecium can be found in ponds with scum on them. It is
covered with tiny hairs that help it move. These hairs are called
cilia. The paramecium is able to move in all directions with its
cilia. The paramecium eats tiny algae, plants, etc. The cilia
propels the food into a tiny mouth opening of the paramecium.
The food is then shoved down a little tube called a gullet that
leads to the protoplasm or stuffing of the cell. The food is held in
little sacs called vacuoles. It has two other vacuoles at either end
of its body to get rid of excess water and wastes. As with the
amoeba, oxygen and carbon dioxide pass through the cell
membrane of the paramecium. The paramecium has two nuclei, a
big and small one. The big one operates as the director of the
cell's activities, rather like a little brain. The smaller one is used
for reproduction. The paramecium splits in half (fission) just as
the amoeba does. First the smaller nucleus splits in half and each
half goes to either end of the paramecium. Then the bigger
nucleus splits and the whole paramecium splits. Occasionally two
paramecium exchange material and form a new paramecium.
This is called conjugation.
Protist #4 : The Volvox
Volvox is one of the best known green algae, and lives in
spherical colonies. Each Volvox is composed of about a thousand
cells, each interconnected and arranged in a hollow sphere.
Volvox is found in ponds and ditches, and even in shallow
puddles. The cells near the back of the colony develop into new
colonies, initially with the flagella directed inwards and held
within the parent. Eventually the parent bursts and the daughter
colonies spread out to form new colonies.
Vocabulary
Eukaryote – cell with a nucleus
Autotroph – makes own food
with photosynthesis
Heterotroph – feeds on other
organisms
Spore – tiny cells released by
fungus-like protists to make new
organisms.
Cilia – hair-like structures on
outside of cell that help it move
Pseudopod – a part of the cell
which sticks out, helping it to move
and to surround food
Protozoa- an animal like protist,
such as an amoeba or paramecium.
Flagellum – whip-like tail on the
outside of cell to help it move
Parasite – organism that
lives/feeds off of or inside another
organism. Can be helpful, harmful
or neither.
Name
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PROTISTS ‘R US
Questions, Assignments & More
What are some common characteristics of protists?
Describe why Euglena can be said to be plant like
AND animal like.
Describe three ways in which protists can move.
What are major differences between a paramecium
and an amoeba?
Explain why a volvox is more similar to a euglena
than an amoeba.
What is unique about paramecium reproduction?
What adaptation helps a euglena get to sunlight?
How is volvox life different than euglena life?
If you were looking at an unknown protist in a
microscope, how could you identify it using the
information you have been provided?
Decide which protist you think is coolest. Tell me why
you think it is cool.
ON THE BACK… time to protist yourself! Make a self portrait of yourself as a protist- you can mix and match
from any cell parts shown in this assignment, plus cell parts from the book. Then, write a paragraph describing
yourself. Both should include at least FIVE cell parts. Coloring would be nice. Please be neat. And, you can
make it fun. Be sure to give yourself a scientific sounding name too. Mine is Schulmecium awesomeus.