12 ch 15protist diversity - algea - endosymbyosis
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Protist Diversity
Dinoflagellates
2000-‐4000 speciesUnique biflagellates
Flagella beat in two different grooves
Causes it to spin like a top when moving
Stiff cellulose plates form theca
Gives them an odd armored appearance
Dinoflagellates
About half are heterotrophicIngest solid food particles or dissolved organic carbon
Even some of the photosynthetic ones may feed in this way-‐-‐-‐mixotrophic
Often are symbionts called zooxanthellae
Lose theca and trade autotrophic production for protection of the elementsCoral reefs
Toxic Blooms
During unfavorable conditions Dinoflagellatesform resting cysts
Under low nutrient levels cysts form, and drop to the bottom, may be transferred by ocean currents, finally germinating up to years later
Acts as method of dispersalExplains why toxic blooms are associated with sewage and agricultural runoff
Pfiesteria actually use toxicity -‐and-‐
Endosymbionts
Contain a diversity of photsynth pigments/ systems
Chl. A + chl. C + carotenoids(peridinin/fucoxanthin) suggest chrysophyteendosymbionts
Green or blue green plastids which suggest ingestion of green algae and/or cryptomonads
Reproduce via longitudinal cell division but sexual repro shows up in multiple lineages
Dinoflagellate Bioluminescence
http://www.youtube.com/watch?v=EN1Yxq8KMsw
Euglenoids
~ 900 species, earliest were most likely particle eaters
Autotrophic Euglenoids contain chl. a and chl. b
Euglenoids most likely get photosynth capabilities from green algae (Chlorophyta)
Euglenoids
Lack a cell wall but contain a pellicle
Allows from some rigidity and flexibility in size of the cell
Also contain a photosensingeyespot stigma
Located near the base of the flagellum (the anterior! end)
http://www.youtube.com/watch?v=hiZ85y0g3UI
Reproduce via lengthwise cytokinesis
No knowledge of sexual Euglenoids
Cryptomonads
Small protists occurring often in cold or subsurface waters
Dominant plankton in either high latitude or seasonal cold water
Once again have colorless phagocytic membersContain phycobilins in addition to chl. a and cStrong evidence for secondary endosymbiosis of red algae (who get their chloroplasts from cyanobacteria)Repro is generally asexual with recent reports of sex in some lineages
Cryptomonads
Haptophytes
Primarily marine ~ 300 species in ~ 80 genera
Most distinctive structure is haptonemaThreadlike structure extending from the cell along with two flagella
Flagella are of equal size and haptonema is reduced
Haptophytes
Coccoliths are another distinguishing character of haptophytes
Calcified scales
Photosynthetic haptophytes contain chl. a and c Some contain fucoxanthin
Similar to brown algae, crysophytes, and diatoms
Chloroplasts also contain chl endoplasmic reticulum
Another sign of secondary endosymbiosis
Coccolith
Haptophytes
Important producers of sulfur oxides
Also contribute 2/3 of all calcium carbonate transfer to deep ocean (carbon sink)
Coccoliths
May also produce ocean blooms covering thousands of square kilometers
Heterokonts
Also referred to as stramenopiles
Flagella usually occur in pairs one ornamented and longer (tinsel) and the other shorter and smoother (whiplash)
Grouping of the four phylum (oomycetes, chrysophytes, diatoms, and brown algae) consistent with molecular phylogenies
Heterokont appears to be a monophyletic character
Heterokonts
Oomycota (water molds)Heterotrophic group
Important plant pathogensSexual reproduction is Oogamus
Female gamete is large and nonflagellatedFamiliar?
Characteristic of some brown, red and green algae as well as bryophytes to vascular plantsOne of the first synapomorphic characters giving us insight into derived plant lineagesAlso prevalent in animal lineages (parallel evolution)
Oomycota
Phytophthoradestruction of many crops
cacao, pineapples, tomatoes, rubber, papayas, onions, strawberries, apples, soybeans, tobacco, and citrus
Can also be a serious problem in turfgrass, golf courses, and athletic fields
Cause of >800,000 deaths during the potato famine
Diatoms
Diverse protist phyla of 100,000 + species
Well preserved fossil record
Can be tremendous in number30-‐50 million individuals of on 1 square cm(!!) of rock
Walls consist of two frustules Overlapping silica halves
Diatoms
Mostly asexualSome sexual forms showing gametic meiosis
Centric forms are oogamousPennate forms are isogamous
Sexual reproduction leads to empty frustuledeposition of SiMay also form resting stages which sink down to the bottom and germinate in more favorable conditions
Frustule halves become progressively smaller
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