Lecture 4 Notes
The Protists
| I. This is a grab-bag kingdom
A. Most organisms are unicellular, but a some are multi-cellular (Volvox) B. Some are plant-like (phytoplankton) and others animal-like (zooplankton) 1. phytoplankton perform photosynthesis and are autotrophs 2. protozoa (of which zooplankton are a one type) are heterotrophs C. All protists are Eukaryotes 1. All eukaryotes have cells with internal organs and membranes 2. But there are two phyla within Protists that have no mitochondria a. mitochondria probably evolved from purple-sulfur bacteria b. these protists without mitochondria probably evolved before this endo-symbiotic event occured, at least 1.5 BYA 3. Appears there were three ways that protists acquired chloroplasts a. red algae - chloroplasts contain chlorophyll a, carotenoids and accessory pigments called phycobilins Their chloroplasts apparently derived from cyanobacteria b. green algae and higher green plants - have chlorophyll a, b, carotenoids, and most likely descended from Prochloron c. brown algae, diatoms, and dinoflagellates - chlorophyll a and c, no b; carotenoids, and yellow & brown pigments Most likely derived from a different bacterial ancestor than red or green algae The Table below shows the distinctions between bacteria, algal and plant groups |
Pigment
composition of those organisms that evolve oxygen during
photosynthesis - From Buchanan
et al. 2000.
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| D. Major groups of Protista
1. Multicellular algae (click here to see picture of algae) a. Green algae - Chlorophyta i. about 7,000 species known ii. mostly freshwater aquatic organisms iii. some grow in moist soil, or even in snow (snow algae) - (Charles Darwin noted the occurrence of red snow in South America in 1835 - didn't know it was because of green algae tinged with anthocyanins, a red pigment) iv. similar biochemically to higher green plants, which are derived from these algae b. red and brown algae i. about 4,000 known species ii. mostly marine algae iii. red algae can grow to great depths in the ocean - deeper than any other photosynthetic organisms iv. many red algae are important food sources in Orient v. brown algae have flagella (none in red algae) vi. about 1500 species of browns vii. Some, like the kelps, can be up to 100 meters long (as tall as the tallest redwood trees!) 2. Unicellular protists a. Most are single celled: paramecium is one example. (Click here to see rotifers, vorticella) b. Many have cilia or flagella, which they wave to move themselves through the water i. cilium - short hairlike projection from surface of eukaryotic cells, with microtubules in a 9 + 2 arrangement. Used to either move an organism through a fluid, or, to move fluid over an organism to bring food to it, or to exchange gases in the water ii. flagellum - longer, hairlike extension from surface of cell (an extension of the plasmamembrane - tubules also in a 9 + 2 arrangement. Used also to move an organism through a fluid c. Zoomastigotes - move by long flagella. Many are parasitic, causing such diseases as sleeping sickness (Tripanosoma sp.) d. Diatoms - 11,500 species. Have a shell made of silicon, in two halves. Are beautiful when viewed under microscope. Microscopic paintings have been done by arranging diatoms under a microscope! (Click here to see picture of diatom) e. Dinoflagellates - perhaps 1000 species. Can cause red tides, which are toxic blooms that kill fish and other organisms and poison shellfish. Other dinoflagellates live symbiotically with corals, providing them with carbon compounds through photosynthesis (which is why coral is restricted to shallow seas) f. Amoebas - no cell walls. Move by extensions of the protoplasm, known as pseudopods. Cause of dysentery. One species in southeastern United States can get in your brain, eat it, and kill you in just a few days. Ugh!! (Click here to see picture of amoeba) g. Sporozoans - major cause of malaria. About 4,000 species in this group About 250 Million people infected each year with malaria - major health problem in tropics. Used to be a problem on SE coast of U.S. in 1700's (Charleston, SC had a bad malaria problem at one time). Children under age 5 most at risk of dying from this. Been very hard to find a vaccine. |
