THE BIG GROUP: the alveolates and stramenophiles

• Dinoflagellates• Apicomplexans• Ciliates• Oomycotes• Diatoms• Chrysophytes• Phaeophyta

Dinoflagellates

• Two flagella- one transverse and one longitudinal

• Important to aquatic food chains.• Responsible for “red tides.” • Some are bioluminescent.• Cellulose “plates” cover

Highlighted SpeciesDinoflagellate

Pfiesteria piscicida• Causes “harmful algal blooms” in certain

conditions.• Produces a toxin but no pigment.• Results in fish kills. May cause human

illness.

Apicomplexans

• Parasitic alveolate. Alveoli- membrane bound sacs.

• Flagellated gametes• Mictrotubule extends from the cell and

pierces the host cell.

Highlighted Species-Apicomplexans

Plasmodium

• Causes malaria (“bad air)• Infects Anopheles mosquitoes which

then bite humans and transmit the motile life stage to the human body.

Ciliates

• All have cilia, which move the cell and assist in moving food toward the cell

• Cilia beat in a synchronized pattern• Contractile vacuoles that expel water from

the body• Has two nuclei

Didinium injesting a Paramecium

Highlighted Species-Ciliates

Paramecium

Oomycotes

• Similar to fungi (oomycotes= egg fungi)• They have diploid nuclei instead of haploid

(as fungi have)• Decomposers• Many are parasitic and prey upon crops

Highlighted Species-Oomycotes

Phytophthora infestans

• Caused the Irish potato famine in the mid 1800.

• Water mold with name meaning “plant destroyer”

• Millions of people died as crops failed several years in a row

Chrysophytes• Group containing diatoms, yellow and golden algae and

coccolithophores

• Mostly photosynthetic

• Coccolithophores- form calcium carbonate plates under their plasma membranes. Created White Cliffs of Dover. Can cause algal blooms which can kill fish.

• Diatoms- Silica shell shaped like a pillbox. Very important primary producers that release about as much free oxygen as plants do on land.

Phaeophyta (Brown Algae)

• Olive green and brown seaweeds• Sargassum- a seaweed growing in the Sargasso sea

Endosymbiotic Theory

• Proposed by Lynn Margulis in 1967.• Explains similarities between prokaryotes

and organelles.• Chloroplasts (and mitochondria) are the

result of endocytosis of photosynthetic bacteria by an anaerobic bacteria.

Endosymbiotic Theory