Protists Chapter 29. 2 Protists Protists are the most diverse of the four eukaryotic kingdoms -Unicellular, colonial and multicellular groups The kingdom.
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Protists
Chapter 29
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Protists
Protists are the most diverse of the four eukaryotic kingdoms
-Unicellular, colonial and multicellular groups
The kingdom Protista is paraphyletic
Some protists are surrounded by Extracellular Material deposited outside of the plasma membrane
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Protists-The 15 major protist phyla are grouped into seven major monophyletic groups-However, 60 lineages cannot be placed with confidence
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Protists
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Eukaryotic Origins
Eukaryotic cells differ from prokaryotes by the presence of a cytoskeleton and organelles
Appearance of eukaryotes in microfossils occurred about 1.5 BYA
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Eukaryotic Origins
The nucleus and endoplasmic reticulum arose from infoldings of prokaryotic cell membrane
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Many organelles evolved via
endosymbiosis between an
ancestral eukaryote and a
bacterial cell
Over time, most organellar genes moved into the nucleus
-Therefore, these organelles cannot be grown in pure culture
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Secondary endosymbiosis -Red and green algae engulfed cyanobacteria-Brown algae engulfed red algae
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General Biology of the Protists
Nutrition
-Phototrophs
-Heterotrophs
-Phagotrophs – Particulate food matter
-Osmotrophs – Soluble food matter
-Mixotrophs are both phototrophic and heterotrophic
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General Biology of the Protists
Asexual reproduction
-Typical mode of reproduction
-Some species have an unusual mitosis
-Binary fission = Equal cells
-Budding = Progeny cell smaller
-Schizogony = Multiple fission
Sexual reproduction
-Union of haploid gametes which are produced by meiosis
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Diplomonads and Parabasalids -Are closely related to the early, now extinct
eukaryotic cell
-Flagellated-Lack mitochondria
Diplomonads-Have two nuclei-Giardia intestinalis Parabasalids
-Have undulating membranes
-Trichomonas vaginalis
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EuglenozoaEuglenoids were among the earliest
eukaryotes to possess mitochondria
-1/3rd have chloroplasts-All have a flexible pellicle
-Stigma – Movement towards light
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Euglenozoa
Kinetoplastids-Unique, single mitochondrion with 2 types of DNA maxicircles and minicircles (expressed genes are used in RNA editing and glycolysis)-Trypanosomes cause human diseases
-African sleeping sickness – Tsetse fly-Escapes immune systems because only one
of 1000-2000 variable antigen genes is expressed at a time on the glycoprotein coat
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Alveolata
Alveolata have flattened vesicles called alveoli
-These function like Golgi bodies below the cell membrane
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AlveolataDinoflagellates
-Unicellular with two unequal flagella-Live in aquatic environments
-Most are photosynthetic
-Reproduction is primarily asexual
-About 20 species produce powerful toxins that harm vertebrates...“Blooms” are responsible for red tide--kills marine vertebrates
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Alveolata Apicomplexans (Spore-forming animal parasites) Plasmodium
-An apicomplexan that causes malaria -Organism has a very complex life cycle
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Alveolata
Ciliates Paramecium-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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Paramecium
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-Food vacuoles = Digestion of food
-Contractile vacuoles = Regulation of water
balance
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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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StramenopilaDiatoms (Phylum Chrysophyta)
-Unicellular organisms
-Have unique double shells made of opaline silica
-Some move using raphes--lined with vibrating fibrils
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Rhodophyta
Rhodophyta, or red algae, range from microscopic to
very large sizes
-Have accessory photosynthetic pigments within
phycobilisomes
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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
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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 CladeForaminifera are heterotrophic marine protists
-Have pore-studded shells called tests, through which thin podia emerge (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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Slime molds w/o a clade1. 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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2. Cellular slime molds
-Individual organisms behave as separate amoebas
-Move through soil ingesting bacteria
-When food is scarce, organisms aggregate to form a moving slug
-Slug differentiates into a sorocarp with spores that differentiate into amoebas again
Slime molds w/o a clade
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