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Biology
Biology
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2. 20-2 Animal-like Protists: Protozoans
Photo Credit: Andrew Syred/Science Photo Library/Photo Researchers, Inc.
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Classification of Protists
One way protists can be classified is by how they obtain nutrition (3 groups):
Heterotrophs are called animal-like protists.
Photosynthesizers are called plantlike protists.
Decomposers and parasites (external digestion) are called funguslike protists.
This classification does not reflect the evolutionary history of these organisms !
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4. Animal-like Protists: Protozoans
Collectively referred of as Zooplankton
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5. 20-2 Animal-like Protists:
Animal-like protists are classified by their means of movement.
There are four phyla of animal-like protists:
zooflagellates
sarcodines
ciliates
sporozoans
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Zooflagellates
Zooflagellates (Zoomastigina)
Animal-like protists that swim using flagella are called zooflagellates.
Motiles
Most zooflagellates are solitary cells. Some form colonies of cells.
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Zooflagellates
Feeding
Generally able to absorb food through their cell membranes.
Many live in lakes and streams, where they absorb nutrients from decaying organic material.
Others live within the bodies of other organisms, taking advantage of the food that the larger organism provides.
Ex: Giardia Trichomonas
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Zooflagellates
Reproduction
Asexual reproduction
Binary fission: Mitosis followed by cytokinesis results in two cells that are genetically identical
Sexual reproduction
Gamete cells are produced by meiosis. When gametes from two organisms fuse, an organism with a new combination of genetic information is formed.
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Zooflagellates
The chanoflagellate, a zooflagellate, is at the origin of the choanocytes in sponges, early animal
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Sarcodines
Sarcodines
Sarcodines are animal-like protists that have pseudopods (pseudo = false, pod = foot).
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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Sarcodines
Amoeba Feeding
Heterotrophic
Endocytosis, food vacuoles
Sarcodines use pseudopods for feeding and movement. The amoeba, a common sarcodine, moves by first extending a pseudopod away from its body. The organism’s cytoplasm then streams into the pseudopod. Amoebas also use pseudopods to surround and ingest prey.
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Sarcodines
Video Amoeba eats two paramecia (ciliate protist) for lunch (43sec):
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Sarcodines
Amoeba Reproduction
Asexual reproduction
Mitosis and cytokinesis
Sarcodines use pseudopods for feeding and movement. The amoeba, a common sarcodine, moves by first extending a pseudopod away from its body. The organism’s cytoplasm then streams into the pseudopod. Amoebas also use pseudopods to surround and ingest prey.
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Sarcodines
Other Sarcodines
Foraminiferans Radiolarians Heliozoans
Sarcodines use pseudopods for feeding and movement. The amoeba, a common sarcodine, moves by first extending a pseudopod away from its body. The organism’s cytoplasm then streams into the pseudopod. Amoebas also use pseudopods to surround and ingest prey.
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Sarcodines
Other Sarcodines
Foraminifers Radiolarians Heliozoans
These groups of protists produce external shells, made out of silica or calcium carbonate, to help support their unusual shapes.
As these protists die the outer shells accumulate on ocean floors. The white cliffs of Dover, England, are huge deposits of calcium carbonate skeletons.
Thanks to their external skeleton, these protists are found as fossils.
Sarcodines use pseudopods for feeding and movement. The amoeba, a common sarcodine, moves by first extending a pseudopod away from its body. The organism’s cytoplasm then streams into the pseudopod. Amoebas also use pseudopods to surround and ingest prey.
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Ciliates
Ciliates
Ciliates use cilia for feeding and movement. Cilia are short hair-like projections that propel a cell.
The internal structure of cilia is identical to flagella.
Ciliates are free living – not parasites or symbionts
Found in fresh or sea water
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Ciliates
Ex. : 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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Ciliates
Structures of a Paramecium (~350µm long)
Ciliates use hairlike projections called cilia for feeding and movement. Ciliates, including this paramecium, are covered with short, hairlike cilia that propel them through the water. Cilia also line the organism’s gullet and move its food—usually bacteria—to the organism’s interior. There, the food particles are engulfed, forming food vacuoles. The contractile vacuoles collect and remove excess water, thereby helping to achieve homeostasis, a stable internal environment.
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Ciliates
Structures of a Paramecium (~350µm long)
Trichocysts:
- Used for defense
- Spiny projections contained in the cell membrane of the organisms
- When the paramecium is in danger, the trichocysts discharge and the spines cover the outside of the paramecium.
Ciliates use hairlike projections called cilia for feeding and movement. Ciliates, including this paramecium, are covered with short, hairlike cilia that propel them through the water. Cilia also line the organism’s gullet and move its food—usually bacteria—to the organism’s interior. There, the food particles are engulfed, forming food vacuoles. The contractile vacuoles collect and remove excess water, thereby helping to achieve homeostasis, a stable internal environment.
trichocyst spines released
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21. Feeding and food Excretion
Zooflagellates
Feeding and food Excretion
Food is caught by cilia, brought to the gullet, engulfed in food vacuoles to the cytoplasm, digested by lysosomes, released by anal pore
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Zooflagellates
Water Excretion
Fresh water protists collect excess water because water passively moves from outside to inside the cell. This passive movement is called osmosis
Contractile vacuoles pump the excess water to outside the cell.
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Water Excretion
Video on contractile vacuole of paramecium (20sec):
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Zooflagellates
Reproduction
Asexual reproduction
- Binary fission (mitosis): normal form of reproduction
Sexual reproduction: Under severe conditions – survival is at stake
- Conjugation (p.502)
- Exchange of DNA between two cells, leads to genetic variability and greater adaptability to environment.
- Technically, conjugation is not reproduction as the process does not results in two new cells. But it is a sexual process.
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Zooflagellates
Conjugation (p502)
1. Two paramecia attach themselves to each other.
2. Meiosis of their diploid micronuclei produces 4 haploid micronuclei but 3 disintegrate.
3. The remaining micronucleus in each cell divides mitotically, forming a pair of identical micronuclei.
4. The two cells exchange one micronucleus from each pair.
5. The macronucleus disintegrate and each cell forms a new macronucleus from its micronucleus.
6. Both cells are now genetically identical.
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Sporozoans
Sporozoans Feeding
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.
Heterotrophic
Plasmodium (cause malaria disease) in human blood
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Sporozoans
Reproduction
Sporozoans reproduce by means of spores
The spores are able to attach themselves to a host cell, penetrate it and then live within it as parasites.
Plasmodium in human blood
Spore phase of Plasmodium
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Sporozoans
Many sporozoans have complex life cycles that involve more than one host.
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29. 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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30. Animal-like Protists and Disease
Malarial Infection
Animal-like protists can cause serious diseases, including malaria. The bite of an Anopheles mosquito can transmit Plasmodium sporozoites. Once in the human body, Plasmodium infects liver cells and red blood cells and multiplies.
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31. Animal-like Protists and Disease
A female Anopheles mosquito bites a human infected with malaria and picks up Plasmodium gamete cells.
Animal-like protists can cause serious diseases, including malaria. The bite of an Anopheles mosquito can transmit Plasmodium sporozoites. Once in the human body, Plasmodium infects liver cells and red blood cells and multiplies.
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32. Animal-like Protists and Disease
The sexual phase of the Plasmodium life cycle takes place inside the mosquito.
Animal-like protists can cause serious diseases, including malaria. The bite of an Anopheles mosquito can transmit Plasmodium sporozoites.
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33. Animal-like Protists and Disease
Infected mosquito bites another human, injecting saliva that contains Plasmodium sporozoites.
Animal-like protists can cause serious diseases, including malaria. The bite of an Anopheles mosquito can transmit Plasmodium sporozoites.
Plasmodium sporozoites
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34. Animal-like Protists and Disease
Sporozoites infect liver cells and multiply asexually.
Plasmodium sporozoites
Liver
Animal-like protists can cause serious diseases, including malaria. The bite of an Anopheles mosquito can transmit Plasmodium sporozoites. Once in the human body, Plasmodium infects liver cells and red blood cells and multiplies.
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35. Animal-like Protists and Disease
Infected liver cells burst, releasing Plasmodium cells called merozoites that infect red blood cells.
Plasmodium sporozoites
Liver
Animal-like protists can cause serious diseases, including malaria. The bite of an Anopheles mosquito can transmit Plasmodium sporozoites. Once in the human body, Plasmodium infects liver cells and red blood cells and multiplies.
Merozoites
Liver cells burst
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36. Animal-like Protists and Disease
Merozoites reproduce asexually inside red blood cells and eventually the infected cells burst.
Plasmodium release toxins, the toxins are transported throughout the body and the symptoms of malaria are produced.
Merozoites
Once in the human body, Plasmodium infects liver cells and red blood cells and multiplies.
Red blood cells
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37. Ecology of Animal-like Protists
Harmful Relationships: Many protists are parasitic, which can affect plants, all types of animals and even other protists. ex. plasmodium – malaria, Trypanosoma – African sleeping sickness, Entamoeba – dysentery
Details on diseases caused by protists: p503
Helpful Relationships: 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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38. 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
pseudopods.
flagella.
cilia.
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
macronucleus.
micronucleus.
trichocysts.
contractile vacuole.
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20–2
One way to classify the various groups of animal-like protists is by
the presence of a nuclear membrane.
the presence of mitochondria.
their means of movement.
the number of contractile vacuoles.
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20–2
Malaria is caused by the sporozoan
Plasmodium.
Anopheles.
Amoeba.
Paramecium.
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