## IM Commentary

The task provides a reasonably straight-forward introduction to interpreting the parameters of an exponential function in terms of a modeling context. In general, an exponential function $f(t)=ab^t$ has two parameters. The parameter $a$ is interpreted as the starting value (when $t$ represents time), and $b$ represents the growth rate -- the amount the quantity is multiplied by each time the value of $t$ is incremented by 1. The task has students both generate an exponential expression from a contextual description, and in reverse, interpret parameters in a context from an algebraic expression.

The task involves some words from biology that might be intimidating to students. Teachers should be prepared to explain that bacteria and protists are very simple single-celled creatures, and clarfiy and confusion around fission -- binary (or multiple) fission is a means of reproduction in which an organism splits into two (or multiple) copies. Alternatively, the task might make a nice connection to students' existing work in a science class.