Transcript Document

Protists
Chapter 29
Protists
Protists are the most diverse of the four
eukaryotic kingdoms
-Unicellular, colonial and multicellular groups
The kingdom Protista is paraphyletic and
grouped for convenience
The 15 major protist phyla are grouped into
seven major monophyletic groups
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Protists
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Protists (Cont.)
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Eukaryotic Origins
The nucleus and
endoplasmic reticulum
arose from infoldings
of prokaryotic cell
membrane
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General Biology of the Protists
Cell surface
-Plasma membrane
-Extracellular material (ECM), in some
-Diatoms – Silica shells
Cysts
-Dormant cell with resistant outer covering
-Used for disease transmission
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General Biology of the Protists
Locomotion
-Flagella
-Cilia
-Pseudopodia (“false feet”)
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General Biology of the Protists
Nutrition
-Phototrophs
-Heterotrophs
-Mixotrophs are both phototrophic and
heterotrophic
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General Biology of the Protists
Asexual reproduction
-Binary fission
-Budding
-Schizogony = Multiple fission
Sexual reproduction
-Union of haploid gametes which are
produced by meiosis
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Diplomonads and Parabasalids
Diplomonads
-Have two nuclei
-Giardia intestinalis
Parabasalids
-Have undulating
membranes
-Trichomonas vaginalis
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Euglenozoa
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Euglenozoa
Kinetoplastids
-Unique, single mitochondrion with DNA
maxicircles and minicircles (RNA editing)
-Trypanosomes cause human diseases
-African sleeping sickness – Tsetse fly
-Leishmaniasis – Sand fly
-Difficult to control because organisms
repeatedly change their protective coat
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Euglenozoa
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Alveolata
Alveolata have flattened vesicles called
alveoli
-These function like Golgi bodies below the
cell membrane
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Alveolata
Dinoflagellates
-Unicellular with two unequal flagella
-Live in aquatic environments
“Blooms” are responsible for red tide
-Most are
photosynthetic
-Do not appear
to be directly
related to any
other phylum
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Alveolata
Dinoflagellates
-Reproduction is primarily asexual
-DNA is not complexed with histones
-About 20 species produce powerful toxins
that harm vertebrates
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Alveolata
Apicomplexans
-Spore-forming animal parasites
-Apical complex is a
unique arrangement
of organelles at one
end of the cell
-Enables the cell
to invade its
host
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Alveolata
Plasmodium
-An apicomplexan that causes malaria
-Eradication of malaria
1. Elimination of mosquito vectors
2. Development of drugs
3. Development of vaccines
-Organism has a very complex life cycle
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Alveolata
Other apicomplexans
-Gregarines
-Found in the intestines
of arthropods, annelids
and mollusks
-Toxoplasma gondii
-Causes infections in
humans with
immunosuppression
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Alveolata
Ciliates
-Feature large numbers of cilia arranged in
longtitudinal rows or spirals around the cell
-Have two types of vacuoles
-Food vacuoles = Digestion of food
-Contractile vacuoles = Regulation of
water balance
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Alveolata
Ciliates
-Have two types of nuclei
-Macronucleus = Divides by mitosis
-Responsible for physiological functions
-Micronucleus = Divides by meiosis
-Involved in conjugation
-Fusion of two cells of different
mating types
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Stramenopila
Stramenopiles have very fine hairs on their
flagella
-A few species have lost their hairs during
evolution
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Stramenopila
Brown algae
-Kelps
-Grow in relatively shallow
waters throughout the world
-Life cycle involves alternation
of generations
-Sporophyte = Multicellular and diploid
-Gametophyte = Multicellular and haploid
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Stramenopila
Diatoms (Phylum Chrysophyta)
-Unicellular organisms
-Have unique double shells made of silica
-Some move using raphes
-Two long grooves lined with vibrating
fibrils
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Stramenopila
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Stramenopila
Oomycetes (“water molds”)
-Were once considered fungi
-Motile zoospores with two unequal flagella
-Undergo sexual reproduction
-Either parasites or saprobes
-Phytophthora infestans
-Irish potato famine (1845-1847)
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Rhodophyta
Rhodophyta, or red algae, range from
microscopic to very large sizes
-Lack flagella and centrioles
-Have accessory photosynthetic pigments
within phycobilisomes
-Origin has been a source of controversy
-Tentatively, treated as a sister clade of
Chlorophyta (green algae)
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Rhodophyta
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Choanoflagellida
Choanoflagellates are most like the common
ancestor of all animals
-Single emergent flagellum, surrounded by
funnel-shaped contractile collar
-Use collar to feed on bacteria
-Have a surface tyrosine kinase receptor
found in sponges
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Choanoflagellida
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Protists Without a Clade
Amoebas are paraphyletic
-Rhizopoda (True amoebas)
-Move by means of cytoplasmic
projections called pseudopods
-Actinopoda (Radiolarians)
-Glassy exoskeletons made of silica
-Needlelike pseudopods
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Protists Without a Clade
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Protists Without a Clade
Foraminifera are heterotrophic marine protists
-Have pore-studded shells called tests,
through which thin podia emerge
-Use podia for swimming and feeding
-Have complex life cycles with haploid and
diploid generations
-Limestones are rich in forams
-White cliffs of Dover
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Protists Without a Clade
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Protists Without a Clade
Slime molds
-Were once considered fungi
-Include two lineages
1. Plasmodial slime molds
2. Cellular slime molds
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Protists Without a Clade
1. Plasmodial slime molds
-Stream along as a plasmodium, a
nonwalled, multinucleate mass of cytoplasm
-Ingests bacteria and other organic material
-When food or moisture is scarce, organism
forms sporangia, where spores are produced
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Protists Without a Clade
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Protists Without a Clade
2. Cellular slime molds
-Individual organisms behave as separate
amoebas
-Move through soil ingesting bacteria
-When food is scarce, organisms aggregate
to form a slug
-Slug differentiates into a sorocarp
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Protists Without a Clade
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