By Ali Paton

The kingdom Protoctista is defined by exclusion.

The members of this kingdom are neither animals, plants, nor prokaryotes.

They comprise these eukaryotic microorganisms and their immediate descendants: all nucleated algae. (This includes sea-weeds) Water moulds which have flagella Slime moulds and slime nets Protozoa

Characteristics of Protoctista  It is a very diverse group with remarkable variation in cell

organisation, patterns of cell division and life cycle. All algae are autotrophs as they are able to photosynthesise. the other forms are heterotrophic. However some change between being autotrophic and heterotrophic

according to condition most have mitochondria

They are all thought to have developed from symbiosis (living together of two species to the advantage of both)

Protoctista can all be grouped together due to their organelle structure, e.g. the form of the membranous structures (cristae) of the mitochondria. In addition the differences in the pigments used for photosynthesis are

used for classification.  Protoctista are aquatic.

They can make their habitat in salt water, freshwater, in moist soil, or within the moist tissues of others.

Laminaria hyperborea Plasmodium falciparium

Amoeba Proteus Cercomonas