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Protist
Most protists are unicellular organisms. A few species are multicellular. All protists
are eukaryotes. Eukaryotes are organisms that have cells with a distinct nucleus and
organelles. Most unicellular protists are microscopic. Some protists are plant-like
because they make their own nutrients through photosynthesis. However, plant-like
protists differ from plants because they do not have roots or stems. Some protists are
described as animal-like. Like animals, these protists do not make their own food and
can move independently. However, these protists differ from animals because most are
single celled. Because they are made up of only one cell, the animal-like protists lack
certain specialized cells, such as nerve and muscle cells, as well as tissues and organs.
Block:
True or False, Circle one.
All protists are unicellular
organisms.
T or F
Complete the sentence.
Protists differ from animals
because…
Volvox
Volvox is a unicellular protist that has chloroplast and gets food by carrying out
photosynthesis. However, unlike most unicellular organisms, Volvox does not live alone.
Instead, this protist forms a group of cells known as a colony. A colony consists of a
hollow sphere that can contain from 500 to 60,000 Volvox. Cells near the surface of the
Volvox colony are specialized to move the entire colony through water. Each of these cells
has two small flagella that are used to propel the colony through water.
Paramecium
Paramecium is a unicellular protist that is common in ponds and in slow-moving
streams. The cell of a Paramecium is almost completely covered with tiny hairs called
cilia that a Paramecium uses for movement. Cilia sweep quickly back and forth to propel
the Paramecium through water. As the Paramecium moves, it feeds on bacteria, algae,
and other tiny organisms. Since Paramecium live in water, they have a contractile
vacuole to pump water out of the cell to keep it from bursting. Paramecium also
contain two nuclei.
How does the Volvox make
food?
How many flagella does a
Volvox use to move?
1
2
4
6 12
Fill & Pick
Paramecium are covered with
tiny hair
s called ___________ which
are used for:
a) Flirtation
b) Movement
c) Digestion
Euglena
Euglena is a unicellular protist that has some characteristics of both plants and
animals. Euglena is similar to an animal because it can move about freely and feed on
other organisms. However, Euglena is similar to a plant because it also has the ability to
make its own food. Euglena cells contain chloroplasts (organelles that store chlorophyll
to capture the sun’s energy and carry out photosynthesis). The Euglena uses light
energy, carbon dioxide, and water to make food. This process is called photosynthesis.
The Euglena has an eye spot within the cell that detects light. When the eyespot detects
light, the Euglena uses its flagella to move toward the light. The flagella is a whip like
tail that moves quickly back and forth to propel the Euglena through water.
How is the Euglena like a
plant?
How is the Euglena like an
animal?
Amoeba
An amoeba is a unicellular protist. Amoebas are often described as animal-like protists
because they are capable of movement and nutrition by feeding on other organisms.
Amoebas move using structures called pseudopods. A pseudopod is an extension of
the cytoplasm that forms when the cytoplasm extends away from the nucleus. An amoeba
pushes a pseudopod forward and the rest of the cell follows. They also use these pods for
feeding. For example, an amoeba may surround another protist with its pseudopods.
The amoeba will then slowly take the other protist into its cytoplasm and digest it.
To move, a Euglena uses:
a) Cilia
b) Flagella
c) Pseudopods
Pseudopods are used for
a) Feeding
b) Movement
c) Digestion
d) All of the above.