creates challenge biologists wish describe catalogue recent developments using dna identify separate species investigate relationship groups various taxonomic scales enormously useful parasitologists many parasites highly degenerate disguising relationships species history cyst imago ''giardia lamblia'' protozoan parasite causes giardiasis species first observed antonie van leeuwenhoek antonie van leeuwenhoek observed illustrated ''giardia lamblia'' linked loose stools first protozoan parasite humans
Natural science Biology Parasitology