Phylum Rhodophyta: Definition and Characteristics

Instructor: Jeremy Battista
Phylum Rhodophyta is a classification of a specific set of red algae. Depending on who you are listening to will determine whether they are protists or plants. We will look here to the origins and specifications of the phylum Rhodophyta.

Defining Rhodophyta

Rhodophyta are a sub-group of algae, the red algae. Even though they are called 'red algae', not all species are necessarily red. Their pigmentation can vary depending on where they are living. Rhodophytes in deeper waters are typically a dark red, almost black color, while those in medium depths are bright red. In shallow areas, the algae can appear more green than red. Some species even have pink or puple coloring.

Their color comes from an accessory pigment (a pigment in addition to chlorophyll), phycoerythrin (similar to chlorophyll) that is found inside of the algae, giving its reddish color. The phycoerythrin absorbs other colors and reflect the red.

Mediterranean red algae

Characteristics of Rhodophyta

Rhodophyta have been identified as some of the oldest and most numerous (up to 10,000 species) of the algae. They primarily live in marine environments, though some species live in freshwater habitats. And although they can live in tropical and polar waters, they are commonly found in reefs and tide pools.

Their taxonomy is currently being disputed as we have moved beyond the typical 5 kingdoms. At one point they would have been classified under the Plantae kingdom or even the Protista kingdom. They are now stuck in a sort of limbo state as far as their taxonomy (classification) goes.

They are eukaryotes, meaning they have membrane-bound organelles as well as a nucleus. This is a step up in the evolutionary line from prokaryotic cells, lacking these features, but Rhodophyta are still not as advanced as other plants similar to them. Rhodophyta are typically multicellular and complex, though there are some red algae made of single cells or simple filaments.

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