Protists 1: Classification and Ecological Roles Flashcards

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1
Q

Whittaker’s Five Kingdom System included the Kingdom Protista

A

Defining characteristic: Eukaryotes that did not fit into the Plant, Animal, or
Fungus kingdoms

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2
Q

Diversity
o Size and complexity

A

 Most protists are unicellular, although some are colonial or multicellular
 Examples
o Unicellular: Euglena
o Colonial: Dinobryon
o Multicellular: Kelp
 Single-celled protists are considered the simplest eukaryotes, but at the cellular
level, many are among the most complex and elaborate of all cells
 Include the same eukaryotic organelles we have discussed
 Include some unique organelles not found in most other eukaryotes

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3
Q

Diversity
o Nutrition

A

 Some are photoautotrophs and have chloroplasts
 Some are heterotrophs, absorbing organic molecules or ingesting larger food
particles
 Others are mixotrophs, using both photosynthesis and heterotrophic nutrition

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4
Q

Diversity
o Reproduction

A

 Some only reproduce asexually (binary fission)
 Some only reproduce sexually (gametes)
 Some have extremely complex life cycles that involve multiple forms of the
organism, some of which reproduce sexually and others asexually (Example:
Plasmodium sp. -> Malaria)

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5
Q

Ecological roles
o Most protists are aquatic and are found almost anywhere there is water

A

 Oceans
 Fresh water
 Damp soil
 Wet leaf litter

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6
Q

Ecological roles
o Some are producers

A

 Photosynthetic protists are THE main producers in aquatic communities
 Photosynthetic protists account for approximately 30% of the total
photosynthesis that takes place on earth
o Photosynthetic protists: 30%
o Land plants: 50%
o Photosynthetic prokaryotes (e.g. cyanobacteria): 20%
 Include
o Diatoms
o Dinoflagellates
o Algae

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7
Q

Ecological roles
o Some are decomposers

A

Help to recycle organic and inorganic matter

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8
Q

Ecological roles
o Some are symbionts

A

 Wood-digesting protists in the guts of termites and ruminants
 Coral reefs
 Photosynthetic dinoflagellates -> carbon
 Coral polyps (animals) -> structure

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9
Q

Ecological roles
o Some are parasites

A

 Examples:
 Plasmodium sp. (Malaria)
 Trichomonas vaginalis (Trichomoniasis [STD])
 Giardia lamblia (Giardiasis [“Beaver Fever”])
 Trypanosoma brucei (African Sleeping Sickness)
 Chryptosporidium parvum (Cryptosporidiosis)
 Toxoplasma gondii (Toxoplasmosis)

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10
Q

Eukaryotic Evolutionary History

A

o Our understanding of eukaryotic evolutionary history has been in flux in recent years
o There is much we don’t know about the evolutionary path of the eukaryotic groups in
existence today

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11
Q

The current hypothesis places all eukaryotes into four major groups (“Supergroups”)

A

Exavata
“SAR Clade
Archaeplastida
Unkonta

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12
Q

Excavata

A

 Diplomonads
 Parabasalids
 Euglenozoans

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13
Q

“SAR’ clade

A

 Stramenopiles
o Diatoms
o Brown algae
 Alveolates
o Dinoflagellates
o Apicomplexans
o Ciliates
 Rhizarians
o Forams
o Cercozoans

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14
Q

Archaeplastida

A

 Red algae
 Green algae
 Land plants

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15
Q

Unkonta

A

 Amoebozoans
o Gymnamoebas
o Slime molds
 Opisthokonts
o Nucleariids
o Fungi
o Choanoflagellates
o Animals

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16
Q

 Supergroups
o Excavata

A

 Excavata refers to a conspicuous feeding groove that appears to have been
“excavated” from one side
 Many lack “classical” mitochondria, but have modified mitochondria or
mitochondrial remnants that show they all originally had them

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17
Q

Supergroups
o Excavata
[] Mitosomes

A

o Only recently discovered
o Remnants of mitochondria
o Same general structure
o No Krebs Cycle, No ETS
o Activity: maturation of Fe-S proteins

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18
Q

Supergroups
o Excavata
[] Hydrogensomes

A

o Same general structure as mitochondria
o Function to produce ATP anaerobically
o Produce hydrogen gas as byproduct

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19
Q

Supergroups
o Excavata
[] Kinetoplast-mitochondrion complex

A

o A single, oversized, mitochondrion contains a dense mass of
many copies of the mitochondrial genome (kinetoplast)
o The complex appears to function like normal mitochondria, just
has a unique structure

20
Q

Parabasalids
o Flagella

A

 Possess a cluster of flagella near the cell anterior
 One long flagellum is attached by an undulating
membrane that spans the length of the cell

21
Q

Parabasalids
o Named for a distinctive structure: parabasal body

A

 Associated with parabasal fibers
 Possibly a modified Golgi complex

22
Q

Parabasalids
o Anaerobic

A

 Lack true mitochondria
 Obtain ATP via hydrogenosomes

23
Q

Parabasalids
o Some form symbiotic relationships in animals

A

 Termites
 Cockroaches
 Ruminants

24
Q

Parabasalids
o Many are parasites

A

 Example: Trichomonas vaginalis
 Disease: Trichomoniasis (STD)
o Men: asymptomatic
o Women:
 More susceptible to 2o
infections
 Genital warts
 Cervical cancer
 Pre-term delivery

25
Q

Diplomonads
o Flagella

A

 Possess multiple flagella, symmetrically located
 Anterior flagella
 Posterolateral flagella
 Ventral flagella
 Caudal flagella

26
Q

Diplomonads
o Nuclei

A

Named for their two identical, symmetrically distributed, niclei

27
Q

Diplomonads
o Lack some common organelles

A

 No lysosomes
 No peroxisomes
 No Golgi apparatus
 No mitochondria

28
Q

Doplomonads
o possess mitosomes (maturation for Fe-S proteins)

A

 Anaerobic
 Fermentative metabolism
o Sugars
o Amino acids

29
Q

Doplomonads

A

o Most are commensal in the intestinal tracts of animals
o A few are free living in stagnant water

30
Q

Doplomonads
o Some are parasitic

A

 Example: Giardia lamblia
 Disease: Giardiasis (“Beaver fever”)
o Diarrhea, abdominal pain, weight loss
o Spreads via cysts in fecal matter
o Obtained by drinking untreated water

31
Q

Euglenozoans
o Flagella

A

 Most have two parallel flagella extending from an apical
pocket near the mouth
 Each flagellum contains paraxonemal, rods

32
Q

Euglenozoans
O two major types

A

 Euglena
 Habitats: free-living (fresh & salt water)
 Mitochondria: normal aerobic function
 Autotrophic
 Photosynthetic
o Possess unique rod chloroplasts
 Some are mixotrophic
o Light: photosynthetic
o Dark: Engulfs prey by phagocytosis
 Kinetoplastids
 Named for the presence of a single large
mitochondrion containing the kinetoplast
 Includes several parasites
o Example: Trypanosoma brucei
 Transmission: insect bite
 Disease: African Sleeping
Sickness
 Stage 1: Fever, headache, joint
pain
 Stage 2: Breaches blood/brain
barrier Changes in behavior,
Coordination problems,
Changes in sleep patterns

33
Q

Stramenopiles
 Possess two dissimilar flagella

A

 Hairy flagellum
 Smooth (hairless) flagellum

34
Q

Stramenopiles
[] Named for the hairy flagellum

A

 Stramen- =straw (referring to flagellum)
 -pile = hair

35
Q

Stramenopiles
o Three major groups

A

Diatoms
Golden algae
Brown algae

36
Q

Diatoms

A

o Key group of photosynthetic protists
o Unicellular
o Silicon dioxide cell wall (frustule)
o Diverse group > 100,000 living species
o Among the most abundant phototrophs in oceans and lakes
o Responsible for sediments known as diatomaceous earth
 Used for:
 Filtration (water filters, swimming pools)
 Abrasives
 Toothpaste
 Skin exfoliators
 Metal polishes
 Pest control
 Anticaking agents (food ingredients)
o So widespread and abundant that blooms affect global CO2
levels
 Use high amounts of CO2 to replicate
 Upon death, sink to ocean floor, tying up organic carbon
for centuries
 Some scientists advocate promoting diatom blooms as a
means of reducing atmospheric CO2 levels

37
Q

Golden algae

A

o Characteristic color results from yellow and brown carotenoids
o All species are photosynthetic
o Some species are mixotrophic
o Most species are unicellular
o Some species are colonial

38
Q

Brown algae

A

o The largest and most complex of the algae
o Characteristic color results from brown carotenoids in their
plastids
o All are multicellular and photosynthetic
o Most are marine (Seaweeds & Kelps)

39
Q

Alveolates
o Characterized by the possession of membrane-enclosed sacs (alveoli) just under
the plasma membrane

A

 Filled with fluids
 Function: unknown
o Temperature regulation
o Strength (thick “skin”)

40
Q

Alveolates
o Groups

A

Dinoflagellates
Apicomplexans
Ciliates
Rhizarians
Unikonts

41
Q

Alveolates
o Groups
- Dinoflagellates

A

o Cells are reinforced by cellulose plates
o Possess a spiral flagellum that lines within a groove between the
plates
o Causes cells to spin as they move
o Mainly marine, some freshwater species
o Diverse nutrition
 Some are photosynthetic
 About half are strictly heterotrophic
 Have plastids
 Indicative of phototrophic ancestors
 Many are mixotrophic
o Responsible for “Red Tide” algal blooms
 Cause massive fish kills
 Toxins
 Oxygen depletion
o Many produce bioluminescence
 Use luciferase and luciferin (substrate)
 Emit a blue-green light
 Light stimulated by disturbance
 May be a defensive strategy
 May startle potential predators
 May attract higher order predators

42
Q

Alveolates
o Groups
- Apicomplexans

A

o Named for a complex at the cell apex that is specialized for
penetrating host cells and tissues
o Possess a unique organelle: Apicoplast
 Contains its own DNA
 Appears to be a vestigial chloroplast
 Non-photosynthetic
 Shows relationship to phototrophs
 Role:
 Lipid biosynthesis
 Iron metabolism
o Nearly all are parasites of animals
 Have intricate life cycles with both sexual and asexual
stages
 Often require two or more host species
 Many are transmitted via insect bite
 Live mainly inside cells, hidden from the host’s immune
system
 Exhibit antigenic variability
 Examples:
 Plasmodium sp.  Malaria
o Transmitted by mosquitoes
o Resides in liver & RBC
o Fever, chills, flu-like symptoms
 Cryptosporidium parvum  Cryptosporidiosis
o Passed via contaminated water
o Explosive diarrhea, low fever,
abdominal pain
 Toxoplasma gondii  Toxoplasmosis
o Passed via contaminated, undercooked
meat, water, or direct contact with fecal
matter (e.g. cat litter box), mother-fetus
o Flu-like symptoms, brain damage,
behavior modifications, eye damage
o 60 million in US infected

43
Q

Alveolates
o Groups
- Ciliates

A

o Named for use of cilia to move and feed
 Cilia of some completely cover cell
 Cilia of some are clustered in rows/tufts
o Most are predators
 Prey
 Bacteria
 Small protists
 Food moved to oral grove by oral cilia
 Enters cell mouth
 Moves to gullet  food vacuoles
 Digestion
o Distinctive feature: two types of nuclei
 Generative nucleus (Micronucleus)
 Diploid, carries cell germline
 Passed from parent to offspring
 Genes are not expressed
 Vegetative nucleus (Macronucleus)
 Polyploid
 Expresses the phenotype of the cell
 Generated from micronucleus
 Amplification & editing
o 10  20,000 chromosomes
o Most contain a single gene
o Reproduction
 Asexual
 Transverse fission, budding, others
 Sexual: Conjugation
 Two cells form a cytoplasmic bridge
 Macronuclei dissemble
 Micronuclei undergo meiosis
 Haploid micronuclei exchange
 Cells separate, new macronuclei form

44
Q

Alveolates
o Groups
- Rhizarians

A

 Amoebas with needle-like pseudopodia
 Use these to move and feed
 Three sub-groups
 Radiolarians
o Intricate internal skeletons of silica
o Pseudopodia radiate outward
o All live in marine environments
o Free floating (planktonic)
 Foraminiferans (Formas)
o Have porous shells of CaCO3
 Most are less than 1 mm in size, but some are much
larger, up to 20 cm long
 Pseudopodia extend through the pores for swimming
and feeding
o Live in both marine and freshwater
 Generally live in sand or attach themselves to rocks or
algae
 Some are abundant in plankton
 Cercozoans
o Common inhabitants of marine, freshwater, and soil ecosystems
o Most are heterotrophs
o Many are predators
 Bacteria
 Small protists
 Fungi
o Some enslave photosynthetic prey
o Some are parasites of plants, animals, or other protists
o Essentially: Similar to Radiolarians and Foraminiferans except
that they have no internal skeleton or shell

45
Q

Alveolates
o Groups
- Archaeoplastida

A

o Generally referred to as Plantae sensu lato
o (“Plants in the broad sense”)
o It is the clade that includes:
 Land plants
 Green Algae
 Red Algae
o Common features:
 All have photosynthetic chloroplasts
 Most have cell walls of cellulose
o Major divisions
 Glaucophyta
 small freshwater single-celled algae
 Chloroplasts have peptidoglycan layer
 Rhodophyceae
 Red algae
 Most are marine seaweeds
 Multicellular
 Red color comes from phycobiliproteins: accessory pigments used in
light capture for photosynthesis
 Chloroplastida
 Land plants and many green algae
 All have chloroplasts without peptidoglycan or phycobiliproteins

46
Q

Alveolates
o Groups
- Unikonts
[] Amoebozoans

A

 Amoeba with lobe- or tube-shaped pseudopodia
 Subgroup 1: Slime molds
o Feed on microorganisms that live on dead plant material: forest
floors, logs, lawns
o Often brightly colored yellows and oranges
o Once thought to be fungi: produce fruiting bodies for spore
dispersal
 DNA sequence analyses indicate that the resemblance
between slime molds and fungi is a case of evolutionary
convergence
 Subgroup 2: Tubulinids
o (Example: Amoeba proteus)
o Unicellular amoeba
o Ubiquitous in soil, freshwater and marine environments
o Most are heterotrophs that actively seek and consume bacteria
and other protists
 Subgroup 3: Entamoebas
o All are parasites
o Infect vertebrates and some invertebrates
o (Example: Entamoeba histolytica)
o Spread via contaminated food and water
o Typically eats bacteria and food particles
o Can start attacking epithelial cells  necrosis
o Enters bloodstream and damages other organs
o Responsible for 100,000 deaths annually

47
Q

Alveolates
o Groups
- Unikonts
[] Opisthokonts

A

 Nucleariids (fungus-like protists)
 Small spherical amoeba with thread-like pseudopodia
 Similar appearance to Rhizarians
 DNA sequencing shows they are more closely-related to fungi
 Thrive in soils and freshwater
 Heterotrophic
o Prey on—
 Algae
 Cyanobacteria
 Choanoflagellates (animal-like protists)
 Choanos (Gk) = funnel
 Free-living unicellular and colonial flagellate eukaryotes
 Ovoid cells with collar of microvilli
 Closely related to animals
 Similar appearance to choanocytes (collar cells of sponges), suggesting a
strong evolutionary relationship
 Movement of the flagellum creates water currents
o Trap bacteria and detritus against the collar  phagocytosis
 Colonial types create extracellular matrix  lorica (basket-shaped
houses)