Number of species in the collection: 19.

Back to Kingdom: Chromalveolata

 

 

Classes:                                             

 

Fragilariophyceae (pennate diatoms lacking rafe)

Phaeophyceae (brown algae)

Pictures of Heterokontophyta:                    

 

 

Characteristics of Heterokontophyta:           

 

The Heterokontophyta is a group of organisms whose name means "unequal, flagellum, plant." This is because, except for some exceptions, they are photosynthetic organisms (and therefore considered plants in older classifications) that have some unicellular life phase with flagella (hair-like structures that move and propel the organism) but with unequal flagella, one short and the other long with small spines (mastigonemes). Their chloroplasts have been obtained through horizontal transfer from a red alga, and therefore they have four enveloping membranes (one from the original cyanobacterium, another from the phagocytic vesicle of the red alga, another from the red alga itself, and the last one from the heterokontophyte phagocytic vesicle). They typically contain chlorophyll a and c, and accessory pigments such as fucoxanthin, which gives them a brown colour.

They are globally distributed organisms, aquatic or found in moist surfaces, in freshwater or saltwater, obtaining their food through photosynthesis. They can be from unicellular and tiny to over 100 m in length. Some unicellular species, apart from the cell wall, have hardened plates or shells, usually made of silicon dioxide.

The following cladogram shows the evolutionary relationships of the different groups within the phylum:

 

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