Common examples of multicellular protists include brown algae, green algae, red algae and slime molds. Algae are classified as plant-like protists, while slime molds are categorized as fungus-like protists.
Eukaryotic organisms contain nucleated cells and specialized structures called organelles. Protists, along with plants, animals and fungi, are generally considered as eukaryotic. Some protists contain only one type of cell, referred to as unicellular protists, while others are composed of different cell types, known as multicellular protists. A colony of protists is usually made up of similar cells with no specialized functions.
Protists are broadly classified according to how they acquire food. Animal-like protists, called protozoans, are unable to synthesize their own food and obtain essential nutrients from external sources. Plant-like protists, called algae, contain chloroplasts and are able to manufacture their own food through photosynthesis. Fungus-like protists, called slime molds, consume decaying organic matter from their surroundings. When there is sufficient food supply, slime molds tend to combine into one multicellular mass known as a plasmodium. Protozoans are sometimes referred to as heterotrophs, algae as photoautrotrophs and slime molds as saprophytes.
Algae are the chief producers for most aquatic organisms and the primary source of oxygen in the planet. The three common types of multicellular algae include brown, red and green algae. Laminaria and nereocystis are common species of brown algae; porphyra and rotalgen are red algae; and spirogyra, volvox and ulva are green algae.