There are six required practicals for Standard Level (SL) IB Diploma Biology course as well as one additional required practical for Higher Level (HL) Biology students. This is my second blog post about each of these required practicals, you can find the Practical 1 or Microscopy practical here . This post is all about Practical 2, or as I call it the Potato Core practical. This lab is an excellent one for students who are learning about osmolarity and collecting reliable and valid data. Like all seven of the practicals they can, and do show up in the IBDP Biology exams; I have seen questions about the skills in this practical in Papers 1, 2 and 3 over the years. It is worth including some of those past paper questions on your unit tests and mock exams to help prepare students for the variety of ways in which the required practicals can be assessed.
Here is the description of Practical 2 which you will find on page 33 of the IBDP Biology Subject Guide: Skill: Estimation of osmolarity in tissues by bathing samples in hypotonic and
hypertonic solutions. (Practical 2). After many years of teaching this practical I have broken it down into the following skills:
When it comes to the required lab skills I tend to approach them in a few different ways depending on how well I know the students (did I teach most of them the previous year), how large the class is (bigger classes make demos rather than individual support more feasible) as well as if there is any new equipment or tools that require an introduction. I often require that students read over the lab procedure (seen below) for homework and plan their methodology. In this lab I have them write their research question, hypothesis and do the required math to figure out how to make their required solutions of salt or sugar.