“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