Ch. 7
Protists
Section 3: Protists
• What is a Protist?
– Protists: are eukaryotes that cannot be classified
by animals, plants, or fungi
– All protists live in moist surroundings
– Protists are diverse because most are unicellular,
but some are multicellular, some are heterotroph,
and autotrophs
– Some protists don’t move, while others zoom
around their moist surroundings
Section 3: Protists
• Animal-Like Protists
– Like animals, animal-like protists are heterotrophs,
and most are able to move from place to place to
obtain food
– Protozoans: animal-like protists, unicellular
Section 3: Protists
• Animal-Like Protists
– Protozoans with Pseudopods
• Pseudopods: “false foot”
• Pseudopods form when cytoplasm flows toward one
location and the rest of the organism follows
• An Amoeba is an example of a protozoan that live in fresh
water
• Small particles, like those of water, pass easily through the
cell membrane into the cytoplasm
• If excess water were to build up inside the cell, the amoeba
would burst
• Contractile vacuole: a structure that collects the extra water
and then expels it from the cell
Section 3: Protists
• Animal-Like Protists
– Protozoans with Cilia
• The second group of animal-like protists are the ciliates
• Cilia: which are hair-like projections from cells that
move with a wavelike motion
• Ciliates use their cilia to move and obtain food
• The cells of ciliates, like the paramecium has two
contractile vacuoles that expel water from the cell.
• Has more than one nucleus
• Produce asexually by binary fission
• What are cilia?
Section 3: Protists
• Animal-Like Protists
– Protozoans with Flagella
• Third group is flagella which are protists that use long, whiplike flagella to move
• Some live inside the body of other organisms
– Example: one type of flagella live inside the intestines of termites
• Symbiosis: interaction between two species; a close
relationship in which at least one of the species benefits
• Mutualism: when both partners benefit from living together
– Example: Giardia is a parasite that lives in humans; comes from
wild animals such as beavers
Section 3: Protists
• Animal-Like Protists
– Protozoans that are Parasites
• Fourth type is characterized by the way they live then
by the way they move
• They are parasites that feed on the cells of body fluids
of their hosts
• Many have more than one host
– Example: Plasmodium: protozoan that causes malaria (disease
of the blood)
– What is symbiosis?
Section 3: Protists
• Plantlike Protists
– Algae: are autotrophs using the suns energy to make their
own food
– Algae play a significant role in the environment
• Example: algae that live near the surface of ponds, lakes, and
oceans are an important food source for other organisms in the
water
– Algae very in size
• Unicellular
• Multicellular
• Live in colonies
– Algae very in color
• They consists of many pigments
Section 3: Protists
• Plantlike Protists
– Diatoms
• Unicellular protists with beautiful glasslike cell walls
• Some float on the surface of water, some attach to
rocks in shallow water
• Food source for heterotrophs
• Move by oozing chemicals out of slits in their cell walls
• When they die, their cell walls collect on the bottom of
lakes or oceans
• Diatomaceous: layer forming coarse substance
Section 3: Protists
• Plantlike Protists
– Dinoflagellates
• Unicellular algae surrounded by stiff plates that look
like a suit of armor
• Exists in different colors such as green or orange
• Glow in the dark
• Have 2 flagella help in grooves between their plates
• When the flagella beat, the dinoflagellates twirl like toy
tops as they move through the water
Section 3: Protists
• Plantlike Protists
– Euglenoids
• Green, unicellular algae that are found mostly in fresh
water
• Can be either autotrophs or heterotrophs
• Whiplike flagellum to help it move
Section 3: Protists
• Plantlike Protists
– Red Algae
• Multicellular seaweed
• Grow more than 260m below the ocean’s surface
• People use red algae in many ways:
– Ice cream
– Hair conditioner
– Eat it fresh, dried, or toasted (Asian cultures)
Section 3: Protists
• Plantlike Protists
– Green Algae
• Very diverse, unicellular, but some form colonies and
are multicellular
• Live in fresh, salt water, or on land found on rocks,
crevices on tree bark, or in moist soils
• Green algae and plants that live on land have similar
characteristics
– Same chlorophyll
Section: Protists
• Plantlike Protists
– Brown Algae
• Example: seaweed, Giant kelp
• Different pigments besides brown are: green, yellow, and
orange
• Plantlike structures: holdfasts, stalks (leaf-like structures),
and gas-filled sacs called bladders
• Live in cool, rock waters off the coast of the Atlantic Ocean
• People eat brown algae and its used as a thickener in
pudding
• What color pigments can brown algae contain?
Section 3: Protists
• Funguslike Protists
– Spore: is a tiny cell that is able to grow into a new
organism
– Like fungi, funguslike protists are hetertrophs, have cell
walls, and use spores to reproduce
– Slime Molds
• Brilliantly colored
• Live on forest floors
• Ooze on the surfaces of decaying materials, feeding on bacteria
and other microorganisms
• Life cycle: tiny amoeba-like cells, use pseudopods to feed and
creep around, cells grow bigger and form a jellylike mass
• When the environment conditions become harsh, the mass
releases spores
Section 3: Protists
• Funguslike Protists
– Water Molds and Downy Mildews
• Live in water or moist places
• Grow as tiny threads and look like fuzz
• Attack many food crops such as: potatoes, corn, and
grapes
• In what environments are water molds found?
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