Do Now: Begin reading the introduction to the algae on your museum visit handout.
Algae are aerobic photoautotrophic eukaryotes. They contain chloroplasts and mitochondria. Almost all of them are aquatic. Algae may be unicellular, colonial, or multicellular. Multicellular forms are not as complex as land plants.
Algae are the main producers in aquatic ecosystems. Without algae, there would be nothing for heterotrophs to eat!
Algae are a diverse group of organisms, with diverse classification and evolutionary history. A few of the more important types are explored here.
Diatoms are best known for their beautiful silica shells. They are unicellular, and are common in fresh and salt water. Also, they produce oils!
Dinoflagellates are very similar to diatoms, because they are unicellular and have a silica shell. The major difference between the two is that dinoflagellates have flagella for movement Some kill sea life.
Brown algae are multicellular algae that contain pigments other than chlorophyll. They are commonly known as kelp.
Red algae are similar to brown algae, except that they have different pigments, giving them their characteristic red color. Agar, and other polysaccharides come from these organisms
Chlorophytes contain chlorophyll, have cellulose cell walls, and thus as a group are most similar to more familiar land plants
Algae and Protists Diversify
Fossils. These multicellular fossils are from a rock formation in Southern China, and are some of the best preserved early eukaryotes ever discovered. The rock formation has been dated to MYA. The journal article presenting the fossil describes 7 different isotope dating techniques that confirm this range.
Some species of algae are colonial in nature. Colonial organisms are different from truly multicellular organisms because individual cells can survive in the environment if separated from the rest of the organism.
Some algae may reproduce asexually or sexually, depending on environmental factors