Extending outwards from the core are the mantle and the crust. Earth's mantle extends to a depth of 2,890 km beneath the surface, making it the thickest layer of Earth. This layer is composed of silicate rocks that are rich in iron and magnesium relative to the overlying crust.
The Parasite: Balantidium coli. Balantidium coli is the only ciliate known to parasitize humans. Ciliates represent a phylum of protozoa characterized, in at least one stage of development, by simple or compound ciliary organelles on the surface of their membranes that are used for locomotion.
To one side of the anterior end, there is funnel-like peristome, which leads to the cytostome or mouth. Balantidium coli trophozoite (left) and cyst (right). Life cycle. Balantidium coli lives in the large intestine where it feeds on bacteria, cells and food particles present in the intestinal lumen.alantidium coli. The ciliate protozoa form a large group of organisms that is characterised by numerous cilia. A large number of ciliates are free-living and an equally large number consists of parasites of the digestive systems of termites, cockroaches and herbivores.