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Biology Biology
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20–2 Animal-like Protists: Protozoans
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20–2 Animal-like Protists: Protozoans
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20-2 Animal-like Protists:
There are four phyla of animal-like protists:
• zooflagellates
• sarcodines
• ciliates
• sporozoansAnimal-like protists are classified by their means of movement.
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20–2 Animal-like Protists: Protozoans
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Zooflagellates
Zooflagellates
What are the distinguishing features of the zooflagellates?
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20–2 Animal-like Protists: Protozoans
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Zooflagellates
Animal-like protists that swim using flagella are called zooflagellates.
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20–2 Animal-like Protists: Protozoans
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Zooflagellates
Flagella are long, whiplike projections that allow a cell to move.
Most zooflagellates have one or two flagella, although a few species have many.
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20–2 Animal-like Protists: Protozoans
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Zooflagellates
Most zooflagellates reproduce asexually by mitosis and cytokinesis.
Some zooflagellates may reproduce sexually.
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20–2 Animal-like Protists: Protozoans
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Sarcodines
Sarcodines
What are the distinguishing features of the sarcodines?
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20–2 Animal-like Protists: Protozoans
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Sarcodines
Sarcodines are animal-like protists that have pseudopods.
Pseudopods are temporary cytoplasmic projections used for feeding or movement.
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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
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Sarcodines
Structures of an Amoeba
Nucleus
Food vacuole
Contractile vacuole
Pseudopods
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20–2 Animal-like Protists: Protozoans
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Sarcodines
Amoebas surround food and engulf it in a food vacuole.
A food vacuole is a small cavity in the cytoplasm that temporarily stores food.
Food is digested and nutrients are passed to the cell.
Waste stays in the vacuole until it is released outside the cell.
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20–2 Animal-like Protists: Protozoans
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Sarcodines
Amoebas reproduce by mitosis and cytokinesis.
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20–2 Animal-like Protists: Protozoans
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Sarcodines
Other sarcodines include:
• Foraminiferans
• Heliozoans (“sun animals”)
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20–2 Animal-like Protists: Protozoans
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Ciliates
Ciliates
What are the distinguishing features of the ciliates?
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20–2 Animal-like Protists: Protozoans
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Ciliates
Ciliates use cilia for feeding and movement.
Cilia are short hairlike projections that propel a cell.
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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
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Ciliates
Structures of a Paramecium
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20–2 Animal-like Protists: Protozoans
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Ciliates
Trichocysts are bottle-shaped structures found just below the surface of the cell membrane.
They are used for defense.
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20–2 Animal-like Protists: Protozoans
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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.
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Ciliates
Cilia sweep food particles into the gullet, an indentation in one side of the organism.
The gullet traps the particles and forces them into food vacuoles. The food vacuoles fuse with lysosomes which contain digestive enzymes.
Once the material in the food vacuole is digested, the waste material empties through the anal pore.
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Ciliates
In fresh water, water moves into the paramecium by osmosis.
Excess water is collected in contractile vacuoles.
Contractile vacuoles are cavities in the cytoplasm that are specialized to collect water.
Once full, they contract, pumping water out of the organism.
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Ciliates
Conjugation
Ciliates reproduce asexually by mitosis and cytokinesis.
When placed under stress, paramecia may engage in conjugation, which allows them to exchange genetic material with other individuals.
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Ciliates
Two paramecia attach themselves to each other.
Meiosis produces four haploid micronuclei, three of which disintegrate.
The remaining micronucleus in each cell divides again.
Macronucleus
Micronucleus
MEIOSIS
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20–2 Animal-like Protists: Protozoans
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Ciliates
The two cells exchange one micronucleus from each pair.
The macronuclei disintegrate, and each cell forms a new macronucleus from its micronucleus.
Exchange of micronuclei
Macronuclei disintegrate
New macronuclei form
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Ciliates
Conjugation is not a form of reproduction. In large populations, conjugation helps produce and maintain genetic diversity.
Genetically identical paramecia form
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Sporozoans
Sporozoans
What are the distinguishing features of the sporozoans?
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20–2 Animal-like Protists: Protozoans
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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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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.
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20–2 Animal-like Protists: Protozoans
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Animal-like Protists and Disease
Animal-like Protists and Disease
How do animal-like protists harm other living things?
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20–2 Animal-like Protists: Protozoans
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Animal-like Protists and Disease
Some animal-like protists cause serious diseases, including malaria and African sleeping sickness.
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20–2 Animal-like Protists: Protozoans
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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
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Animal-like Protists and Disease
Malarial Infection
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20–2 Animal-like Protists: Protozoans
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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
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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
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Animal-like Protists and Disease
Gametes fuse to form zygotes, meioses occurs, and sporozoites are produced and migrate to salivary gland.
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20–2 Animal-like Protists: Protozoans
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Infected mosquito bites another human, injecting saliva that contains Plasmodium sporozoites.
Animal-like Protists and Disease
Plasmodium sporozoites
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20–2 Animal-like Protists: Protozoans
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Sporozoites infect liver cells and multiply asexually.
Animal-like Protists and Disease
Liver
Plasmodium sporozoites
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20–2 Animal-like Protists: Protozoans
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Infected liver cells burst, releasing Plasmodium cells called merozoites that infect red blood cells.
Animal-like Protists and Disease
Plasmodium sporozoites
Liver
Liver cells burst
Merozoites
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Animal-like Protists and Disease
Red blood cells
Merozoites
Merozoites reproduce asexually inside red blood cells.
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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.
Red blood cells
Merozoites
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20–2 Animal-like Protists: Protozoans
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Animal-like Protists and Disease
Other Diseases Caused by Protists
African sleeping sickness
Amebic dysentery
Giardia
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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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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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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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20–2
Which human disease is caused by the protist Trypanosoma?
a. measles
b. African sleeping sickness
c. malaria
d. diarrhea
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