Top tips for teaching biology when you’re a chemist

In many UK secondary schools, teaching out of specialism is no longer the exception – it’s the norm. Timetables, recruitment pressures and the structure of secondary school science courses mean that chemistry specialists frequently find themselves teaching biology, sometimes with little notice and limited support. Although this can feel daunting, it doesn’t have to be a barrier to good learning. In fact, chemistry teachers bring strengths that can be powerful assets in the biology classroom, aiding interdisciplinary learning while building teacher skills. 

I am a biology specialist. I’ve taught all three sciences for GCSE and have worked closely with chemistry specialists stepping into biology. I’ve watched excellent chemistry teachers lose confidence when faced with unfamiliar biological language, exam mark schemes that seem vague or topics that don’t behave like tidy reaction equations. These experiences have convinced me that most of the challenge lies not in the content itself, but in how biology thinks.

Biology isn’t just chemistry with plants

One of the biggest differences between biology and chemistry is the nature of certainty. Chemistry often deals in defined systems: reactions go to completion, rules are precise and models are tightly bounded. Biology, by contrast, is messier. It is full of tendencies, ranges and exceptions. Processes are influenced by environment, variation and scale, and exam answers frequently reward description and interpretation rather than calculation.

Biology is full of tendencies, ranges and exceptions 

Biology is also deeply conceptual. Topics such as homeostasis, natural selection or the immune response rely on linked chains of cause and effect that play out over time. There is practical work, of course, but many biological investigations are about patterns and variables rather than definitive outcomes. While it is easy to provide real-world contexts for most topics – such as health, disease, ecosystems and inheritance – students must also learn how to apply core ideas flexibly rather than recall isolated facts.

Play to your chemistry strengths

As a chemistry specialist, you already have great skills for biology: precision, clarity and respect for evidence. The key is to adapt how these are expressed.

• Be explicit with language. Biology is terminology heavy, and many words sound familiar but mean something very specific (e.g. adaptation, efficiency, response). Students often fail biology questions because they use imprecise wording, not because they don’t understand the idea. Model good answers out loud, unpack command words and insist on careful phrasing – just as you would with chemical equations.
• Treat models as stories. In chemistry, models often explain what is happening at a particulate level. In biology, models usually explain why something happens over time. Diagrams of the heart, a reflex arc or photosynthesis are not just labelled pictures – they are narratives. Encourage students to walk through a process step by step, explaining consequences at each stage.
• Anticipate misconceptions. Biology is full of intuitive but incorrect ideas: that plants get food from soil, that evolution is purposeful, or that organs work in isolation. Chemistry teachers are often excellent at confronting misconceptions head-on. Ask students to predict outcomes, justify reasoning, then use evidence to challenge flawed thinking.
• Don’t oversimplify to the point of inaccuracy. A common trap is trying to make biology feel more like chemistry by reducing everything to neat rules. Although simplification is necessary at GCSE/Standard level, avoid absolute statements that will have to be un-taught later. For example, enzymes don’t stop working at high temperatures, they denature.
• Use exam materials early. Biology mark schemes often credit specific language, phrasing and sequencing, so make use of past questions. Share success criteria with students to build everyone’s confidence in what good looks like. Treat exam questions as curriculum tools that clarify emphasis, depth and common pitfalls and not just as an assessment.

These suggestions are a starting point for chemistry teachers to teach biology; experiment and see what works for you and your learners. And if you’re teaching physics as a chemistry (or biology) specialist, read this article by physics teacher Martin Coombes.