Transcript Unit 8 Notes (Protista)

Kingdom Protista
• Characteristics
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Algaelike or plantlike
Protozoa or Animallike
Funguslike
Unicellular
Multicellular
Eukaryotes
Kingdom Protista
Algaelike or Plantlike
• All obtain energy by photosynthesis.
• All have chlorophyll a, but may have various other
chlorophylls and different accessory pigments.
• Phyla
– Euglenophyta
• One to three flagella, at their apical (leading) end
– Dinoflagellates
• Two flagella- one is posterior, while the second is transverse
and rest in an encircling mid groove perpendicular to the first
flagellum.
• Some are bioluminescent.
• Others produce nerve toxins that concentrate in filter-feeding
shellfish, which then cause illness in human when eaten.
Kingdom Protista
Algaelike or Plantlike
• Phyla
– Chrysophyta
• Golden algae
• Have one or two apical flagella
– Diatoms
• Shells made of silica (SiO2)
– Chlorophyta
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Green algae
Have both chlorophyll a and b
Cellulose cell walls
Store their carbohydrates as starch
Believed to be the ancestors of plants
Variation in sexuality.
Kingdom Protista
Algaelike or Plantlike
• Phyla
– Phaeophyta
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Brown algae
Multicellular
Have flagellated sperm cells.
Some are giant seaweeds or kelps
Kingdom Protista
Protozoa or Animallike
• Heterotrophs
– Consume either living cells (being predatory or
parasitic) or dead organic matter.
• Phyla
– Rhizopoda
• Amoebas
• Move by extensions of their of their cell body called
pseudopodia.
• Pseudopodia encircle food and absorb it by phagocytosis
Kingdom Protista
Protozoa or Animallike
• Phyla
– Zooflagellates
• Flagellated protozoa
• Some mutualistic species digest cellulose in the guts
of termites.
• Others are parasites, such as Trypanosoma, which is
transmitted by the tsetse fly and cause African
sleeping sickness in humans.
Kingdom Protista
Protozoa or Animallike
• Phyla
– Sporozoa
• Parasites of animals
• No physical means of motility
• They form spores which are dispersed by one or
more hosts that participate in the completion of their
life cycle
• Sporozoan that causes malaria, spends part of its life
cycle in mosquitoes and part in humans.
Kingdom Protista
Protozoa or Animallike
• Phyla
– Ciliophora
• Distinguished by their cilia, which they use for moving.
• Specialized structures
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Mouth
Anal pore
Contractile vacuoles for water balance
Two kinds of nuclei (macronucleus and several small
micronuclei)
• Paramecium
Kingdom Protista
Funguslike
• Resemble fungi because they form either
filaments or spore-bearing bodies similar to
fungi.
• Three divisions:
Kingdom Protista
Funguslike
• Acrasiomycota (cellular slime molds)
– Exhibit both funguslike and protozoalike characteristics
during their life cycle.
– Spores germinate into amoebas which feed on bacteria.
– When food sources are depleted, the amoebas aggregate
into a single unit, which migrates as a slug.
– The individual cells of the slug then mobilize to form a
stalk with a capsule at the top similar to the sporebearing bodies of many fungi.
– Spores are then released, which repeat the cycle when
they germinate.
Kingdom Protista
Funguslike
• Myxomycota (plasmodial slime molds)
– Grow as a single, spreading mass (plasmodium) feeding
on decaying vegetation.
– When food becomes unavailable or when the
environment desiccates, stalks bearing spore capsules
form.
– Haploid spores released from the capsule germinate
into haploid amoeboid or flagellated cells which fuse to
form a diploid cell.
– The diploid cell grows into the spreading plasmodium.
Kingdom Protista
Funguslike
• Oomycota (water molds, downy mildew,
and white rust)
– They are either parasites or saprobes.
– They are much like fungi in that they form
filaments (hyphae) which secret enzymes that
digest the surrounding substances.
– The breakdown products of digestion are then
absorbed.
Kingdom Protista
Evolution of Eukaryotes
• Cellular structures and processes unique to
eukaryotes:
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Membrane-enclosed nucleus
Mitochondria
Chloroplasts
Endomembrane system
Cytoskeleton
Multiple chromosomes consisting of linear DNA
molecules compactly arranged with proteins.
– Life cycles that include mitosis, meiosis, and sex.
Kingdom Protista
Evolution of Eukaryotes
• First process in eukaryotic evolution:
– Specialized infoldings of the prokaryotic
plasma membrane, may have produced:
• Nuclear envelope
• Endoplasmic reticulum
• Golgi apparatus
Kingdom Protista
Evolution of Eukaryotes
• Second process in eukaryotic evolution:
– Endosymbiosis hypothesis, Lynn Margulis,
University of Massachusetts
• Probably led to the mitochondria and chloroplast
• Proposes that mitochondria and chloroplast were formerly
small prokaryotes living within larger cells.
• Proposed ancestors of mitochondria were aerobic heterotrophic
prokaryotes that became endosymbionts.
• Proposed ancestors of chloroplasts in early eukaryotes were
photosynthetic prokaryotes, probably cyanobacteria, that
became endosymbionts.
Kingdom Protista
Evolution of Eukaryotes
• Evidence (mitochondria/chloroplast to bacteria)
– Endosymbiotic relationships in the modern world.
– Appropriate size
– Inner membranes have several enzymes and transport
systems that resemble those found on the plasma
membrane of modern prokaryotes.
– Replicate by a splitting process similar to binary fission
in bacteria.
– Contain a genome consisting of circular DNA not
associated with histones or other proteins.
Kingdom Protista
Evolution of Eukaryotes
• Evidence (mitochondria/chloroplast to bacteria)
– Contain transfer RNA, ribosomes, and other items
needed to transcribe and translate their DNA into
proteins.
– Ribosomes are more similar to prokaryotic ribosomes.
• Size
• Biochemical characteristics
• Sensitivity to certain antibiotics
– Lang and Burger, University of Montreal
• Found that mitochondrial genome of the protist Reclinomonas
americana closely matches that of bacteria in structure and
function.