Heterokont means “different flagella”. Organisms in this group are eukaryotes that have a life stage with two different flagella, one whiplash and one ornamented. In addition to this shared feature, heterokonts have a diplontic life cycle. The earliest heterokonts were heterotrophic. These often function as decomposers or parasites in aquatic ecosystems, and primarily as plant pathogens in terrestrial ecosystems. The Irish potato famine was caused by one of these.
At some point in history, a heterotrophic heterokont tried to eat an ancestor of the red algae. This photosynthetic, red alga-like organism was not digested and, instead, evolved slowly over time into a four-membraned chloroplast. This process is called secondary endosymbiosis and is described in more detail later in the lab.