Balantidium coli has 2 contractile vacuoles. Although contractile vacuoles are common to ciliates, they are rare in parasitic protozoa, which suggests that Balantidium coli has a unique osmoregulatory capacity.Balantidium coli has 2 developmental stages: a trophozoite stage and a cyst stage.alantidium 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.
A variable that remains unchanged or held constant to prevent its effects on the outcome and therefore may verify the behavior of and the relationship between independent and dependent variables. Supplement. Control variables are important in scientific experiments to test the validity of the results.For instance, in an experiment on Boyle's law, the temperature must be kept constant so that the outcome from the experiment can be regarded as valid.ontrol variables are important in scientific experiments to test the validity of the results. For instance, in an experiment on Boyle's law, the temperature must be kept constant so that the outcome from the experiment can be regarded as valid.
What are dependent variables and controlled variables? In an experiment, the independent variable is altered, and the effect observed is the dependent variable, or outcome. The controlled variable is intended to be kept the same tâ¦hroughout the experiment so that changes in it do not affect the results. 2 people found this useful.