The Kingdom Protista
What Is a Protist?
• Classification of Protists
• One way protists can be classified is by how they
obtain nutrition:
– Heterotrophs are called animal-like protists.
– Photosynthesizers are called plantlike protists.
– Decomposers and parasites are called funguslike protists.
Animal-like Protists:
Protozoans
20-2 Animal-like Protists:
• There are four phyla of animal-like protists:
•
•
•
•
zooflagellates
sarcodines
ciliates
sporozoans
– Animal-like protists are classified by their
means of movement.
Zooflagellates
• Zooflagellates
– What are the distinguishing features of the
zooflagellates?
Sarcodines
• Sarcodines
– What are the distinguishing features of the
sarcodines?
Sarcodines
• Amoebas
• Amoebas are flexible, active cells with
thick pseudopods that extend out of the
central mass of the cell.
• Cytoplasm streams into the pseudopod,
and the rest of the cell follows.
• This type of locomotion is known as
amoeboid movement.
Structures of an Amoeba
Contractile vacuole
Pseudopods
Nucleus
Food vacuole
Sarcodines
• Amoebas reproduce by mitosis and
cytokinesis.
Ciliates
• Ciliates
– What are the distinguishing features of
the ciliates?
Ciliates
• Structures of a Paramecium
Ciliates
• Paramecia possess two types of nuclei:
• The macronucleus keeps multiple copies
of most genes that the cell needs in its
day-to-day existence.
• The micronucleus contains a copy of all
of the cell's genes.
Sporozoans
• Sporozoans
– What are the distinguishing features of the
sporozoans?
Sporozoans
• Many sporozoans have complex life cycles
that involve more than one host.
• Sporozoans reproduce by sporozoites.
• A sporozoite can attach itself to a host cell,
penetrate it, and then live within it as a
parasite.
Animal-like Protists and Disease
• Animal-like Protists and Disease
– How do animal-like protists harm other living
things?
Animal-like Protists and Disease
• Malarial Infection
Animal-like Protists and Disease
• A female Anopheles mosquito bites a human
infected with malaria and picks up
Plasmodium gamete cells.
Animal-like Protists and Disease
• The sexual phase of the Plasmodium life
cycle takes place inside the mosquito.
Animal-like Protists and Disease
• Gametes fuse to form zygotes, meioses
occurs, and sporozoites are produced and
migrate to salivary gland.
Animal-like Protists and Disease
• Infected mosquito bites another human,
injecting saliva that contains Plasmodium
sporozoites.
Plasmodium
sporozoites
Animal-like Protists and Disease
• Sporozoites infect liver cells and multiply
asexually.
Plasmodium sporozoites
Liver
Animal-like Protists and Disease
• Infected liver cells burst, releasing
Plasmodium cells called merozoites that
Plasmodium sporozoites
infect red blood cells.
Liver
Merozoites
Liver cells
burst
Animal-like Protists and Disease
•Merozoites reproduce asexually inside red
blood cells.
Merozoites
Red blood cells
Animal-like Protists and Disease
•Infected red blood cells burst, releasing
merozoites that infect other red blood cells.
Some cells release gametes that can infect
mosquitoes.
Merozoites
Red blood cells
Plantlike Protists: Unicellular Algae
Plantlike Protists
• Plantlike protists contain chlorophyll and
carry out photosynthesis.
• Plantlike protists are commonly called
“algae.”
• Algae are sometimes classified with the
plants.
Plantlike Protists
• The four phyla of unicellular algae are:
•
•
•
•
euglenophytes
chrysophytes
diatoms
dinoflagellates
Euglenophytes
• Euglenophytes
– What are the distinguishing features of the
euglenophytes?
Euglenophytes
Pellicle
Carbohydrate
storage bodies
Contractile vacuole
Chloroplast
Nucleus
Eyespot
Gullet
Flagella
Euglenophytes
• Near the gullet is a
reddish pigment
known as the
eyespot, which helps
find sunlight to power
photosynthesis.
• Euglenas can also
live as heterotrophs.
Eyespot
Euglenophytes
• Euglenas do not
have cell walls.
Instead, they have
an intricate cell
membrane called a
pellicle.
• The pellicle folds
into ridges, each
supported by
microtubules.
Pellicle
Euglenophytes
• Euglenas reproduce asexually by
binary fission.
Chrysophytes
• Chrysophytes
– What are the distinguishing features of
the chrysophytes?
Chrysophytes
• The cell walls of some chrysophytes
contain the carbohydrate pectin rather
than cellulose, and others contain both.
• Chrysophytes store food in the form of oil
rather than starch.
• They reproduce both asexually and
sexually.
• Most are solitary, but some form threadlike
colonies.
Diatoms
• Diatoms
– What are the distinguishing features of
the diatoms?
Dinoflagellates
• Dinoflagellates
– What are the distinguishing features of
the dinoflagellates?
Dinoflagellates
• Dinoflagellates have two flagella that fit in
grooves between two thick plates of
cellulose that protect the cell.
• Most dinoflagellates reproduce asexually
by binary fission.
• Many dinoflagellates are luminescent.
When they are agitated, they give off light.
Plantlike Protists: Red, Brown, and
Green Algae
Plantlike Protists: Red, Brown,
and Green Algae
• The three phyla of algae that are largely
multicellular are:
• red algae
• brown algae
• green algae
Red Algae
• Red Algae
– What are the distinguishing features of red
algae?
Brown Algae
• Brown Algae
– What are the distinguishing features of brown
algae?
Brown Algae
• Brown Alga Structure
Blades
Bladder
Stipe
Holdfast
Green Algae
• Green Algae
– What are the distinguishing features of green
algae?
Funguslike Protists
– What are the similarities and differences
between funguslike protists and fungi?
Slime Molds
• Slime Molds
– What are the defining characteristics of the
slime molds?
Slime Molds
• Two groups of slime molds are
recognized:
• Cellular slime molds, whose individual cells
remain separated during every phase of the mold's
life cycle.
• Acellular slime molds, which pass through a
stage in which its cells fuse to form large cells with
many nuclei.
Slime Molds
– Cellular Slime Molds
• Most cellular slime molds live as free-living cells
that are not easily distinguishable from soil
amoebas.
• In nutrient-rich soils, these amoeboid cells
reproduce sexually and produce diploid zygotes.
Slime Molds
•Life Cycle of a Cellular Slime Mold
Fruiting
body Spores Emerging
amoebas
Solitary cell
Aggregated
amoebas
Zygote
Fruiting body
Migrating colony
Slime Molds
• When food is scarce, the cells produce
spores.
• They emit chemicals to attract cells of the
same species.
• Cells gather into a colony that functions
like one organism.
Slime Molds
• The colony moves slightly, then stops to produce a
fruiting body, a slender reproductive structure
that produces spores.
• Then the spores are scattered from the fruiting
body.
• Each spore produces one cell, starting the cycle
again.
Slime Molds
– Acellular Slime Molds
• Acellular slime molds begin as amoeba-like cells.
• When they aggregate, their cells fuse to produce
structures with many nuclei known as plasmodia.
Slime Molds
•Life Cycle of an Acellular Slime Mold
Fertilization
Mature
sporangium
Spores
Germinating
Young
sporangium
Feeding
Mature plasmodium
plasmodium
Zygote
Water Molds
• Water Molds
– What are the defining characteristics of the
water molds?
Water Molds
FERTILIZATION
MEIOSIS
SEXUAL
REPRODUCTION
ASEXUAL
REPRODUCTION