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“Plant-Like” Protists:
Unicellular Algae
Unicellular Algae
• Chlorophyll and accessory pigments allow algae to harvest and use energy from sunlight.– Both give algae a wide range of colors
Phylum Euglenophyta - Euglena
• “Plant-like” protists that have two flagella but no cell wall
• Red eye-spot – helps organism find sunlight to power photosynthesis
• Phototrophic autotroph or heterotroph (absorb nutrients in decayed organic material)
• Pellicle – cell membrane• Reproduce asexually by binary
fission
Euglena Anatomy
Gullet
Chloroplast
NucleusEyespotFlagella
Carbohydrate storage bodies
Pellicle
Contractile vacuole
Phylum Pyrrophyta - Dinoflagellates
• Half are photosynthetic, half are heterotrophs
• Two flagellas• Reproduce asexually by
binary fission• Some luminescent/give
off light• Only eukaryote with no
histones to help store DNA
Phylum Chrysophyta
• Mostly solitary• Yellow-green and golden-
brown algae• Gold-colored chloroplasts• Cell walls contain pectin
rather than cellulose; others can have both pectin and cellulose
• Reproduce asexually and sexually
• Store oil, not starch
Phylum Bacillariophyta – Diatoms
• Most abundant organisms on Earth
• Thin, silicon cell walls
Ecology of Unicellular Algae
• Helpful:– Phytoplankton – diatoms and dinoflagellates– 70% of photosynthesis occurs in ocean– Symbiosis – corals and dinoflagellates –
Tridacha gigas (clam) and dinoflagellates• In both cases, algae provide food to the animal
Ecology of Unicellular Algae• Harmful:
– Algae “blooms” – dangerous toxin produced by algae – shellfish eat the algae and eat the toxin = people can’t eat it
– Dinoflagellate Gonyaulx – red tide
“Fungus-like” Protists
• Heterotrophs that absorb nutrients from dead or decaying matter. Unlike true fungi, “fungus-like” protists have centrioles and lack chitin in cell walls
• Recyclers of dead organisms
Slime Molds
• Play key roles in recycling organic material
• 3 Phyla of slime molds– Phylum Acrasiomycota– Phylum Myxomycota– Phylum Oomycota
Phylum Acrasiomycota
• Cellular slime molds – Begin life as amoeba-like cells– When food begins to run out, then form colonies and
produce a fruiting body which produces spores– Spores “hatch” into amoeba-like cells
Phylum Myxomycota
• Acellular slime molds – Begin life as amoeba-like
cell, called plasmodia, that contain thousands of nuclei but only one cell membrane
– Plasmodia may reach several meters in diameter
– Form fruiting bodies – Produce haploid spores
which germinate into flagellate cells which fuse to produce the diploid “amoeba”
Phylum Oomycota
• Water molds– Thrive on dead or decaying organic matter in water
and are plant parasites on land– Hyphae – thin filaments– A water mold caused the potato famine in Ireland in
1840s