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Biology
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Before starting Protists, a video on Cordyceps: attack of the killer fungi (3min):
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20-1 The Kingdom Protista
Photo Credit: Andrew Syred/Science Photo Library/Photo Researchers, Inc.
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Protists are eukaryotes that are not members of the Plant, Animal, or Fungi kingdoms.
In Greek, Protista means “the very first” : Protists are the first eukaryotic organisms on Earth
What Is a Protist?
What Is a Protist?
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Evolution of Protists
Origin of the first eukaryotic cell: Mitochondria (first engulfing) and chloroplasts (2nd engulfing) in eukaryotic cells may have descended from prokaryotes that lived inside larger cells (Endosymbiosis). 2 1
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What Is a Protist?
The kingdom Protista may include more than 200,000 species.
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Most, but not all, protists are unicellular.
Solitary Colonial Multicellular
Single cell life Usually unicellulars Differentiated cells with
living as a group specific functions
Ex. Chlamydomonas Ex. Volvox Ex. Ulva
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8. 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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9. Classification of Protists
Protists are difficult to classify because they often have characteristics in common with more than one of the three groups
Ex.: Euglena
photosynthetic (plant-like)
+ flagella (animal-like)
Powerful tools of molecular biology illuminate more and more the true evolutionary phylogeny of protists.
At present, biologists don’t agree on how to classify the protists. Therefore, we will take the traditional approach.
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Video Protist Rap song (2m30s):
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20-1
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20-1
A protist is any organism that is not a plant, an animal, a fungus, or a prokaryote.
True
False
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20-1
Funguslike protists are
autotrophic.
photosynthetic.
parasitic.
chemosynthetic.
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20-1
Animal-like protists are
autotrophs.
heterotrophs.
decomposers.
producers.
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20-1
Biologists have difficulties classifying protists because
their DNA cannot be examined.
evidence suggests that they evolved from so many different groups.
structural similarities used for classification are difficult to detect.
their ancestors may have evolved through symbiosis.
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20-1
An organism is classified as a protist if it
resembles any other member of the Eukarya domain.
shares DNA sequences that are found only in other protists.
has a cell wall made of cellulose.
does not belong in any other kingdom of the Eukarya.
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