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.
A control variable is the one that stays the same. A controlled variable is a variable that is kept the same between the control group and experimental group, so that only the â¦ experimental (independent) variable is allowed to change.+ 41 others found this useful.hat are kept constant to ensure that it is only the Independent Variable causing an effect on the Dependent Variable. 2 people found this useful. Edit. Share to: 1  A Look at JavaScript Variable Types Similar to other programming languages, JavaScript variables are containers used to hold values and expressions.