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Chapter 8-1
What are Protists?
What are Protists? –the “Junk Drawer”
kingdom
• A protist is a member of a group of
eukaryotic organisms which have a
membrane-bound nucleus.
• Most protists reproduce asexually,
though some can reproduce sexually
• Protists are extremely diverse and
share characteristics with plants,
animals, and fungi but are not
classified as any of these groups
What are Protists?
• General characteristics– Most are unicellular, but some, such as the
giant kelp, are multicellular & can grow to be as
big as 100 meters
– Live in moist surroundings
– Some move and some don’t
– Some can make their own food, while others are
consumers or decomposers
– They are classified by how they obtain food
• Scientists classify protists as plant-like, animal-like,
or fungus-like based on which group they most
resemble.
Three kinds of Protists-
• Plant-like
• Animal-like
• Fungus-like
Plant-like Protists
• Like plants, these protists use chlorophyll for
photosynthesis
– (takes place in chloroplasts)
• Almost all live in water
• Examples include:
–
–
–
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Algae
Diatoms
Dinoflagellates
Euglenoids
Plant-like Protists- Algae
• Algae are plant-like protist that
perform photosynthesis. They
can be either multicellular or
unicellular.
• Red algae
– Used to make ice cream,
marshmallows & shampoo
• Brown algae
– Known as “seaweed”
• Green algae
Plant-like Protists- Diatoms
• A type of microscopic plantlike protist with
a hard outer wall is a diatom
– Unicellular with glasslike cell walls
– Used in silver polish, toothpaste & insulation
Plant-like Protists- Dinoflagellates
• Dinoflagellates are
unicellular plantlike protists
that use flagella to move.
– They have many pigments
so they come in several
colors
– They have 2 flagella that
allow them to swirl around
as they move
– They glow in the dark & look
like fireflies at night
Plant-like Protists- Euglenoids
• A Euglenoid is a unicellular plant-like
protist that has a flagellum at one end of
its body. It has no cell wall. Instead it has a
rigid rubbery coat called a pellicle.
• Euglenoids
– Have eyespots that
respond to changes in
light
• Tell the euglena when to perform photosynthesis
– Produce food by photosynthesis
Click on the image below to observe a
Euglena swimming with it’s flagella
The importance of Algae
• Algae provide food for
animals and animal-like
protists, and provide shelter
for many aquatic organisms
such as sea otters.
• They are plant-like but have
holdfasts rather than roots.
• Algae can help remove
pollution from the water.
Algae are thought to cause Red Tides
•Pollution can be a food source for algae, allowing the
population of algae to increase quickly.
•This overproduction can lead to Red Tides, which can be
dangerous to other aquatic animals & humans
Animal-like Protists: Protozoans
• Protozoans are protists that resemble tiny
animals
• Protozoans are unicellular and mostly live
in wet environments.
• Protozoans do not have chloroplasts and
cannot make their own food.
– They are consumers and some are parasites
Animal-like Protists- Ciliates
• Cilia are short, hair-like structures that
grow on the surface of some protists.
• Protists with cilia are called Ciliates.
• Cilia cover the surface of the cell and
move a protist through water.
• Ciliates reproduce asexually, but they can
exchange some genetic material through a
process called conjugation.
Animal-like Protists- Ciliates
• A paramecium is a protist with cilia and
two types of nuclei.
• A paramecium gets its food by forcing
water into the oral groove in its side.
Click on the video below to observe
a paramecium feeding!
Animal-like Protists- Flagellate
• A Flagellate is a type of protozoan with
one or more flagella.
• Flagellates eat decaying matter.
Animal-like Protists- Sarcodines
• Sarcodines are animal-like protists with
no specific shape.
• An amoeba is one common Sarcodine.
• An amoeba moves and obtains nutrients
by using pseudopods, which means
temporary or false foot.
• Amoeba form pseudopods by slowly
pushing their cytoplasm against the soft,
flexible cell membrane.
Animal-like Protists: Protozoa cont’
• Amoeba use their pseudopods to engulf
their food and form a food vacuole
• They are found in soil, salt & fresh water,
and use a contractile vacuole to get rid of
excess water
Click on picture below to observe
an Amoeba in action!!!
The Importance of Protozoans:
Some protozoans are parasites and can
cause disease like malaria.
Animal-like Protists: Protozoa cont’
• Spore forming protist,
Plasmodium
Fungus-like Protists
• Funguslike protists share many
characteristics with fungi.
• Slime molds are funguslike protists
composed of cell material and nuclei
floating in a slimy mass.
• Most slime molds absorb nutrients from
other organic matter in their
environment.
Funguslike Protists
• A water mold is a
funguslike protist that
lives as a parasite or
feeds on dead
organisms.
• Slime molds and water
molds usually
reproduce sexually
when environmental
conditions are harsh or
unfavorable.
Importance of Funguslike Protists
• Funguslike protists play a valuable role in
the ecosystem by breaking down dead
plants and animals, making nutrients
available for living organisms.
• Many funguslike protists attack and
consume living plants.
• Water mold destroyed more than half of
Ireland’s potato crop in 1845