2. What is a Protist?
• The kingdom Protista is a diverse group that may include more than 200,000 species
• Biologists have argued for years over the best way to classify protists, and the issue
may never be settled
• In fact, protists are defined less by what they are and more by what they are not
Protist - ________________________________________________________________
_______________________________________________________________________
_
• Most protists are unicellular, but some are multicellular
Evolution of Protists
• The kingdom “Protista” means “the very first” which is appropriate because they
were the first eukaryotic organism on Earth
• It is hypothesized that the first Protists evolved from a symbiosis of several
prokaryotic cells
Endosymbiotic theory - ____________________________________________________
_______________________________________________________________________
_
_______________________________________________________________________
_
2
3. Classification of Protists
• Protists are so diverse that biologists suggest that they should be broken up into
several kingdoms
• Currently biologists don’t agree how this should be done
• Therefore we will look at Protists as if they belong in the same kingdom and classify
them by how they obtain nutrition
Animal-like Protists
• Heterotrophs - ________________________________________________________
• Many are capable of locomotion
o Flagella –
o Cilia –
o Psuedopods –
o Sporozoans –
Plasmodium (malaria)
Plant-like Protists
• Many protists contain the green pigment chlorophyll and carry out photosynthesis
• Autotrophic
• However, they are not classified as plants, they are algae
Ecology of Unicellular Algae
• Plant-like protists play a major ecological role on earth
• They make up a large part of the phytoplankton
Phytoplankton - __________________________________________________________
_______________________________________________________________________
_
_______________________________________________________________________
_
• About ______ of photosynthesis on earth occurs in phytoplankton
3
4. Algal Blooms
• Sometimes populations of algae grows in enormous masses called _______________
• These algal blooms deplete the water of nutrients and can release toxins into the water
Ex.)
Fungus-like Protist
• Like fungi, the fungus-like protist are heterotrophs that absorb nutrients from dead or
decaying organic matter
• But unlike true fungi, fungus-like protists have centrioles
• They also lack the chitin cell walls of true fungi
Slime molds
• Slime molds are fungus-like protists that play a key role in recycling organic material
• Found in places that are damp and rich in organic matter
Water Molds
• Fungus-like protists that thrive on dead decaying organic matter in water and some
are plant parasites on land
Ecology of Fungus-like Protists
• They are important as recyclers or organic material
• They can cause diseases however
o Mildews and blights
o Potato famine 1845 and 1851
4
5. Name __________________________________ Date __________________ Per ______
Chapter 20 Review
1. What is a protist?
2. What are the three methods that protists use to obtain food?
3. What is the role of unicellular algae in the environment?
4. How are fungus-like protists and fungi similar? How are they different?
5. What is the role of slime molds in the environment?
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