Helping you explore how science works with post-16 students

Lesson B: Cell membranes

Key facts

  • Relevance: AS/A Biology
  • Time: 60 minutes

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Activities, including OHTs, background information and student sheets:


Experimental data provide the basis from which scientific understanding of the natural world develops. However, scientific understanding does not emerge unproblematically from the data without the creative, intuitive thinking of scientists. In other words, scientists have to decide what kind of data to collect, and how to think about that data in order to build scientific knowledge about the world.

In situations where there is more than one model available, new evidence may support one model more than the others. In these situations scientists need to decide whether such evidence is sufficient for them to shift their support to this model.

The overall focus of this teaching is to make clear to students that scientific understanding does not just emerge from experimental data, and to develop their confidence in evaluating the extent to which evidence supports scientific explanations. 


The lesson aims to help students develop their understanding of the role of theoretical models in science. In particular that:

  • producing models involves conjecture and creative thinking; 
  • competing models can arise; 
  • further scientific research can lead to the acceptance of one model as a consensus view. 


This lesson consists of three activities.

Activity B1

Students are asked to evaluate a straightforward conclusion drawn from experimental evidence.

Activity B2

Students evaluate two competing models in the light of contemporary evidence and identify the parts of the models that are not evident from the data.

Activity B3

Students re-evaluate the two models and a third, more recent, model in the light of further evidence. It should now be clear how the increased amount of evidence supports a single model.