Chapter 18 : Kingdom Protista
2 billion years old. Total of roughly 60,000 species. Eukaryotic, usually aerobic.
Often single celled, many live in water.
Divided into 3 groups : protozoa, algae, slime molds.
Subkingdom Protozoa (animal-like)
Chemoheterotrophs (take in food).
1) Phylum Actinopoda
Usually marine. Single cells.
class Heliozoa have long axopods to catch prey eg Actinophrys.
class Radiolaria have a hard silica shell, which forms sediment at the bottom of the ocean after it dies, and can be used to see changes in ocean temperature. Oceans. It also forms limestone (used to build the pyramids in Egypt).
2) Phylum Kinetoplastida ( zooflagellates )
One or two flagella; elongated mitochondria.
eg Trypanosoma causes sleeping sickness in Africa in cattle and people.
Trypanosomiasis. It is spread by a biting fly (tsetse fly).
Trypanosoma cruzi causes Chagas disease in S.America (no cure). It is spread by a "kissing bug" that feeds around the lips at night.
3) Phylum Rhizopoda
They change the shape of the cell to form pseudopodia for movement.
eg Amoeba
Amoeba video.
Difflugia covers itself with sand grains to form a shell with only one opening.
4) Phylum Sporozoa
Parasites that form a resistant spore.
eg Plasmodium causes malaria. Malaria kills over 1 million people a year, mainly in Africa, and is spread by mosquito. Research
5) Phylum Ciliophora
Live in freshwater and move using many cilia on the cell surface. eg Paramecium
Video
Subkingdom Algae
Photoautotrophs ( photosynthetic ). Different groups have different pigments : eg red algae have phycobilins.
Commercial importance : edible seaweed, agar (for growing bacteria), algin (used to thicken food, make toothpaste, put a good head on beer, make leather etc), diatomaceous earth (for car polish, and kills insects).
Main groups of algae: red algae, green algae, diatoms and dinoflagellates.
1) Phylum Rhodophyta ( red algae )
5,000 species. Seaweeds, usually tropical, often found in deep water.
They are important producers in coral reefs.
Red algae store energy as "Floridean starch"
Red algae.
example : Polysiphonia
2) Phylum Chlorophyta ( green algae )
10,000 species, often freshwater. They store plant starch, and are the ancestors of land plants. Green algae.
They can reproduce sexually or asexually.
Some green algae form lichens with fungi (ascomycetes).
examples : Chlamydomonas single celled.
Volvox and Pediastrum form colonies.
Spirogyra has colonies in filaments, that reproduce sexually through conjugation tubes.
Ulva or "sea lettuce" is edible.
3) Phylum Bacillariophyta ( diatoms )
10,000 species. Freshwater and marine. Often light brown in color, they are surrounded by two silica shells. Diatoms
store energy as oil ( for buoyancy) , as well as leucosin.
Diatomaceous earth is used in filters, polish, lubricants and insecticides. Product.
example : Navicula
4) Phylum Dinoflagellates
5,000 species, mainly marine. The cells are protected by thick plates : theca.
They move using two flagellae . Some are mutualistic living inside coral.
Large numbers cause "red tides" that can kill fish and marine mammals. Antitoxins from red tides might be useful in treating cystic fibrosis. Examples : Ceratium,
Karenia
One genus is predatory, killing and eating fish: Pfiesteria
Subkingdom : Slime molds
They have some characteristics of fungus (decomposers, and produce spores) and some characteristics of animals (movement).
Phylum Myxomycota
Usually orange or yellow. They decompose dead plants or animals. Individual cells clump together to form a plasmodium that creeps around to feed. Dog vomit slime mold!
Reproduce sexually to form resistant spores: eg Trichia
Dictyostelium is used to make proteins (in biotechnology).
Last edited November 2009, by David Byres, dbyres@fscj.edu