Biology
Biology
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20-1 The Kingdom Protista
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What Is a Protist?
Protists are eukaryotes that are
not members of the Plant, Animal,
or Fungi kingdoms.
The kingdom Protista may include more than
200,000 species.
Most, but not all, protists are unicellular.
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Classification of Protists
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.
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Animal-like Protists: Protozoans
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20–2 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.
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20–2 Animal-like Protists:
Protozoans
Zooflagellates
Zooflagellates
Animal-like protists that swim using flagella
are called zooflagellates.
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20–2 Animal-like Protists:
Protozoans
Sarcodines
Sarcodines
Sarcodines are animal-like protists that
have pseudopods.
Pseudopods are temporary cytoplasmic
projections used for feeding or movement.
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20–2 Animal-like Protists:
Protozoans
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.
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20–2 Animal-like Protists:
Protozoans
Sarcodines
Structures of an Amoeba
Contractile vacuole
Pseudopods
Nucleus
Food vacuole
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20–2 Animal-like Protists:
Protozoans
Ciliates
Ciliates
Ciliates use cilia for feeding and
movement.
Cilia are short hairlike projections that
propel a cell.
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20–2 Animal-like Protists:
Protozoans
Ciliates
Paramecia
One type of ciliate is a paramecium.
In a paramecium, the cilia are grouped into rows
and bundles, and beat in a regular pattern.
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20–2 Animal-like Protists:
Protozoans
Ciliates
Structures of a Paramecium
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20–2 Animal-like Protists:
Protozoans
Sporozoans
Sporozoans
Sporozoans do not move on their own—
they are parasitic.
Sporozoans are parasites of a wide variety of
organisms, including worms, fish, birds, and
humans.
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20–2 Animal-like Protists:
Protozoans
Sporozoans
Many sporozoans have complex life cycles that
involve more than one host.
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20–2 Animal-like Protists:
Protozoans
Animal-like Protists and Disease
Malaria
Malaria is one of the world’s most serious
infectious diseases, killing as many as 2 million
people each year.
The sporozoan Plasmodium, which causes
malaria, is carried by the female Anopheles
mosquito.
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20–2 Animal-like Protists:
Protozoans
Animal-like Protists and Disease
Malarial Infection
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20–2 Animal-like Protists:
Protozoans
Animal-like Protists and Disease
A female Anopheles mosquito bites a human infected
with malaria and picks up Plasmodium gamete cells.
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20–2 Animal-like Protists:
Protozoans
Animal-like Protists and Disease
The sexual phase of the Plasmodium life cycle takes
place inside the mosquito.
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20–2 Animal-like Protists:
Protozoans
Animal-like Protists and Disease
Infected mosquito bites another human, injecting
saliva that contains Plasmodium sporozoites.
Plasmodium
sporozoites
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20–2 Animal-like Protists:
Protozoans
Animal-like Protists and Disease
Sporozoites infect liver cells and multiply asexually.
Plasmodium sporozoites
Liver
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20–2 Animal-like Protists:
Protozoans
Animal-like Protists and Disease
Infected liver cells burst, releasing Plasmodium cells
called merozoites that infect red blood cells.
Plasmodium sporozoites
Liver
Merozoites
Liver cells
burst
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20–2 Animal-like Protists:
Protozoans
Animal-like Protists and Disease
Merozoites reproduce asexually inside red blood
cells.
Merozoites
Red blood cells
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20–2 Animal-like Protists:
Protozoans
Ecology of Animal-like Protists
Ecology of Animal-like Protists
Many animal-like protists are essential to the living
world.
• Some live symbiotically within other organisms.
• Some recycle nutrients from dead organic
matter.
• Some live in water, where they are eaten by
tiny animals, which in turn serve as food for
larger animals.
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20–2 Animal-like Protists:
Protozoans
Ecology of Animal-like Protists
Some animal-like protists are beneficial to other
organisms.
The protist Trichonympha lives within the digestive
systems of termites.
It breaks down cellulose, allowing termites to digest
wood.
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20–2
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Continue to:
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20–2
Structures found in sarcodines that are used for
feeding and movement are known as
a. pseudopods.
b. flagella.
c. cilia.
d. food vacuoles.
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20–2
The structure found in most ciliates that contains
a “reserve copy” of all the cell's genes is the
a. macronucleus.
b. micronucleus.
c. trichocysts.
d. contractile vacuole.
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20–2
One way to classify the various groups of
animal-like protists is by
a. the presence of a nuclear membrane.
b. the presence of mitochondria.
c. their means of movement.
d. the number of contractile vacuoles.
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20–2
Malaria is caused by the sporozoan
a. Plasmodium.
b. Anopheles.
c. Amoeba.
d. Paramecium.
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