How do biologists model changes in a population?

When the per capita rate of increase ( r) takes the same positive value regardless of the population size, then we get exponential growth. When the per capita rate of increase ( r) decreases as the population increases towards a maximum limit, then we get logistic growth.

halogen, any of the six nonmetallic elements that constitute group 17 (group viia) of the periodic table. the halogen elements are fluorine (f), chlorine (cl), bromine (br), iodine (i), astatine (at), and tennessine (ts).