Kingdom Protoctista comprises the eukaryotic microorganisms and their immediate descendants: all algae, including the seaweeds, undulipodiated (flagellated) water molds, the slime molds and slime nets, the traditional protozoa, and other even more obscure aquatic organisms. Its members are not animals (which develop from a blastula), plants (which develop from an embryo), or fungi (which lack undulipodia and develop from spores). Nor are protoctists prokaryotes. All protoctist cells have nuclei and other characteristically eukaryotic features. Many photosynthesize (have plastids), most are aerobes (have mitochondria), and most have undulipodia with their kinetosome bases at some stage of the life cycle. All protoctists evolved from symbioses between at least two different kinds of bacteria - in some cases, between many more than two. As the symbionts integrated, a new level of individuality appeared.