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CHAPTER 20: Protists
High School Biology Class
Kingdom Protista
• Sometimes called “The Catchall Kingdom”
because the organisms in it are those that
have eukaryotic cells, but are NOT fungi,
plants, or animals.
• Usually protists are identified by what they
are NOT (i.e. bacteria, fungi, plant, or
animal) rather than what they actually are.
What is a Protist?
• Protists - are members of the Kingdom Protista,
a large and extremely varied group.
• There are currently over 115,000 species (very
diverse) of protists that have been classified.
What is a Protist?
• The only trait that all protists have in common is
that they all have a nucleus (eukaryotic cells).
• Protists are the hardest kingdom of organisms to
classify because they do NOT share many traits.
Protist Examples
Protist Facts
• The word protist is from from the Greek word
protistos, which mean “first.”
• Knowing this makes it easier to remember that
protists were the “first eukaryotes” to evolve.
– Fossils indicate that Protists arose about 1.5 mya.
Protist Facts
• Scientists hypothesize that protists evolved from
bacteria that had formed symbiotic relationships.
(Theory of Endosymbiosis)
Protist Types
• Scientists also hypothesize that protists
diverged to create the Fungi, Plant and
Animal Kingdoms.
• Therefore, there are three types of Protists:
1) Fungi-like Protists
2) Plant-like Protists
3) Animal-like Protists
Plant-like
Animal-like
PROTISTS
Fungi-like
Characteristics of Protists:
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Some photosynthetic (like plants)
Some ingest food (like animals)
Some absorb food (like fungi)
All are Eukaryotic
Some with cell walls (some without)
Unicellular OR Multicellular
Autotrophic OR Heterotrophic
They Were the 1st Kingdom to Exhibit:
* Sexual reproduction
* Multicellularity
* Mitosis and Meiosis
* Complex flagella and cilia
Sexual Reproduction
Flagella
Cilia
Other Names Include:
• Protozoa = Heterotrophic protists
• Algae = Autotrophic (Photosynthetic) protists
Protozoa
Algae
Reproduction:
• Usually protists reproduce ASEXUALLY in one
of the following manners:
- Mitosis
(like in fungi/animal/plant cells)
- Binary Fission
(like in bacteria)
Reproduction Continued:
• Sometimes protists reproduce SEXUALLY:
* Sexually in “Unicellular Protists”
- During unfavorable conditions (lack of food and other
resources) pairs of gametes fuse together into a
zygote with a thick protective wall (zygospore).
Reproduction Continued:
• Sometimes protists reproduce SEXUALLY:
* Sexually in “Multicellular Protists”
- Alternation of Generations = having both diploid
and haploid phases.
Reproduction Continued:
• Sometimes protists reproduce SEXUALLY:
* Sexually in “Multicellular Protists”
- Conjugation = a union of two protists to
exchange genetic material.
Type of Animal-like Protists:
1. Sarcodines (Rhizopoda)
Example: Amoebas
• Pseudopodia (false feet) - cytoplasmic extensions for
movement and feeding.
Facts:
- Parasites
- Disease = Entamoeba histoltica
- Binary Fission
Amoebas proteus
Type of Plant-like Protists:
2. Diatoms (Bacilliarophyta)
– Photosynthetic, unicellular protists with
unique double shells (made of silica) that
looks like glass.
Facts:
- Reproduce asexually
- Found in oceans and lakes
Diatoms
Type of Plant-like Protists:
3. Algae – Phototrophs
– Green Algae (Chlorophyta) – have the same
pigments (chlorophyll A & B) as in plants.
– Produce 30-50% of the Earth’s Oxygen
Green Algae
Type of Plant-like Protists:
3. Algae - Phototrophs
– Red Algae (Rhodophyta) - multicellular organisms
found in warm ocean waters.
– May live near in water or on land.
Red Algae
Type of Plant-like Protists:
3. Algae - Phototrophs
– Brown Algae (Phaeophyta) - multicellular and found mostly in
cool marine type environments.
Example: Kelp
• The largest organism on Earth.
Brown Algae
Kelp
Type of Plant-like Protists:
3. Algae - Phototrophs
– Golden Algae (Chrysophyta) – unicellular or multicellular
organisms that show a great deal of diversity as both
autotrophs and heterotrophs.
Golden Algae
Type of Plant-like Protists:
4. Dinoflagellates (Dinoflagellata)
– Unicellular, phototrophs with 2 flagella that
are used for movement.
Facts:
- Parasites
- Disease = Red Tide
- Binary Fission
Dinoflagella
Red Tide
• Red Tide is the term used to describe the rapid reproduction
of plankton (dinoflagellates). Red Tide affects soft-shell clams,
mussels, oysters, and scallops.
• Symptoms include tingling in fingers, lips, and tongue as well as
headaches, dizziness, nausea, muscular paralysis and respiratory paralysis.
Type of Animal-like Protists:
5. Zoomastigotes (Zoomastigina)
–
Unicellular, heterotrophs with one flagella.
Example: Trypanosomes
• Protists that can cause African Sleeping Sickness.
Facts:
- Parasites or symbionts
- Disease = Trypanosoma gambiense
- Binary Fission or Meiosis
- Termites need them to live (digest cellulose)
Trypanosomes
African Sleeping Sickness
• African Sleeping Sickness is caused by the tsetse flies
which bites a person or animal and injects the
trypanosome protist into the victim.
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Among the first symptoms and signs of African sleeping sickness are
headaches, irregular fevers, swollen tissues and joint pains.
At a later stage the parasites invade the brain, which usually leads to mental
disorders, coma and eventually death.
Type of Plant-like Protists:
6. Euglenoids (Euglenophyta)
– Freshwater, unicellular protists with two flagella.
Example: Euglena
a) Pellicide - protein layer inside cell membrane.
b) Eyespot – (photoreceptor) moves toward light.
Type of Animal-like Protists:
7. Ciliates (Ciliophora)
– Cilia - short flagella (hairs) used for movement.
– Unicellular heterotrophs with two nuclei.
Example: Paramecium
• Reproduce by mitosis or conjugation.
Facts:
- Macronucleus = cell growth
- Micronucleus = cell reproduction
- Contractile Vacuole – pumps water out
Paramecium
Type of Fungi-like Protists:
8. Cellular Slime Molds (Acrasiomycota)
– Resemble amoebas, but during environmental stress,
they form colonies that reproduce by spores.
Fuligo septica
Type of Fungi-like Protists:
9. Plasmodial Slime Molds (Myxomycota)
– Plasmodium - mass of cytoplasm that
looks like oozing slime (contain 1,000 nuclei).
Physarum
Type of Fungi-like Protists:
10. Water Molds (Oomycota)
– Parasites with two flagella (1 in front and 1 in back).
Saproglenia
Type of Animal-like Protists:
11. Sporozoans (Sporozoa)
– Parasitic protists that form spores during reproduction.
– Cause malaria and toxoplasmosis.
Facts:
- Parasites
- Disease = Plasmodium species
- Disease = Toxoplasmosis gondii
- Nonmotile
Complicated Life Cycle
Malaria
• Malaria is caused by the mosquito which bites a person
or animal and injects the plasmodium protist into the
victim.
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Malaria can cause a variety of symptoms including general malaise, fever,
vomiting, pain, anemia, and convulsions.
If left untreated, some infected individuals can lapse into a coma, and severe
anemia is often a cause of death.
Protist Diseases:
~ Protists cause diseases in humans and animals (Page 490 Table 22-3)
Protists Are Beneficial As Well:
1) Human and Animal Digestion
Example: Cattle can digest hay and grass because various protists
can help them break it down into simpler substances.
Protists Are Beneficial As Well:
2) Plankton in Oceans Support Food Chains
Example: Plankton/Algae are the largest group of organisms that can
perform photosynthesis and thus make food for others.
Protists Are Beneficial As Well:
3) Photosynthesize and Produce Oxygen
Example: Algae are the largest group of organisms that can
perform photosynthesis and thus make oxygen for others.
ALGAE
Protists Are Beneficial As Well:
4) Recycle Nitrogen, Carbon and Phosphorus
Nitrogen Cycle
Carbon Cycle
Phosphorus Cycle
Protist Fun:
Any Questions?
• “Information is the currency of democracy.”
--Ralph Nader
• “There is an old saying that the course of
civilization is a race between catastrophe and
education. In a democracy such as ours, we
must make sure that education wins the race.”
--JFK