Using more plant-based examples when teaching A Level Biology

I am the head of biology at Hills Road Sixth Form College in Cambridge but on Fridays I work with Science and Plants for Schools (SAPS). As part of my work for SAPS I have been collating a list of ideas for using plant-based examples when teaching biology. I’ve compiled them into an Excel spreadsheet, so it is searchable and filterable. It’s called Getting plants into your biology teaching and is available from the SAPS website in the Growth Hub.

In this blog I’ll share the benefits that I think using plant-based examples throughout biology bring to students and discuss three examples from my teaching.

The benefits of using plant-based examples throughout A Level Biology

In my mind, the benefits of using more plant-based examples fall into two categories. Firstly, there are academic benefits that will help students become more successful in their A Levels and develop better thinking skills. This in turn will make them better scientists in the future if they choose that route. Secondly, there are wider benefits for students, including career opportunities, and for society as a whole.

Including plant-based examples across biology helps to breakdown the perceived divide between ‘animal topics’ and ‘plant topics’. It’s then easier for students to see how general biological principles apply across all life. They can see how life’s solutions to various problems are often fundamentally the same but vary widely in the details of how the problem is addressed.

On a more pragmatic level, apart from their own bodies, the most regular access students have to biology outside the classroom is via plants. Or at least it can be if they make the link between what they learn in lessons and what they see in the world around them. Crisps, chocolate, tea, coffee, trees, bushes, grass, and weeds in cracks in the pavement are all teeming with biology. If we link more of what we teach to the things that biology students see around them then maybe they will think about their biology more. They might, if we’re lucky, chat about it with their friends and family!

Wider benefits for students include a greater appreciation of the natural world, a greater enjoyment of all topics in A Level Biology (including the plant ones), and the opening up of possible career paths that they may not have previously considered. Students who are keen to become scientists in fields such as biochemistry or genetics will have a wider range of opportunities if they are open to considering plants as their model organism. However, possibly the most important benefit of all is that society needs more plant-positive people and more plant scientists to help address some of the world’s most pressing problems (such as the climate emergency, the biodiversity crisis and our ability to feed the world’s growing population).

Three examples of using plant-based examples

Peas to hair

When introducing the ‘Biological molecules’ topic (2.1.2) I like to emphasise the central role that plants play in making the organic molecules that we use to build our bodies. It also helps to get across that all life is made from the same building blocks – we just put them together in different ways. The story I tell is how we make hair from peas. It goes something like this:

1. A pea plant growing in a field not too far from here makes amino acids which it gives to its developing offspring, the new peas.
2. The developing peas package the amino acids into storage proteins so they can use them in their early, independent life before they can make enough of their own.
3. When the peas are fully developed but before they have a chance to have an independent life of their own, they are harvested by a farmer, frozen and packaged up into bags.
4. The bags of frozen peas are transported to supermarkets, and you come along and buy them.
5. At home you cook and eat them, maybe even sneaking a frozen pea or two before the rest are cooked – delicious!
6. In your stomach and small intestine, the pea storage protein is hydrolysed back into amino acids.
7. The amino acids are absorbed into your blood stream and travel through your circulatory system into the capillaries in the skin on your head.
8. Your hair-making cells take in the amino acids from the blood and use them, in different proportions and in a different sequence than they were in the pea storage protein, to build your hair.
9. So next time you eat some peas do say thank you for making amino acids so you can grow wonderful hair.

The role of enzymes

After the ‘Enzymes’ topic (2.1.4), I spend a lesson trying to embed the idea that one of the things that makes life such an incredible thing is that its systems are ‘self-organising’. For instance, development is the self-organisation of cells into tissues, organs and organ systems, and metabolism is a self-organising set of chemical reactions. In this lesson students use the context of how a plant must partition the glucose it produces in photosynthesis (for respiration, storage as starch and production of cellulose for growth) to design a system that makes appropriate ‘decisions’. 

From the activity students see that enzymes are at the heart of how chemistry becomes biology, not for their catalytic properties but because of the way they can regulate reactions and be regulated themselves. Students see that the foundation of biology is ‘decision-making’ chemistry. The resources for this lesson along with a more in-depth discussion of it are on a webpage called Engage your students with enzymes on the SAPS website.

Convergent evolution of caffeine

My favourite example of convergent evolution I use when teaching the ‘Classification and evolution’ topic (4.2.2) comes from a paper in Proceedings of the National Academy of Sciences (PNAS). Huang et al., show that the production of caffeine has evolved independently in chocolate (Theobroma cacao), tea (Camellia sinensis) and coffee (Coffea arabica) as well as two other plants, guarana (Paullinia cupana) and oranges (Citrus sinensis). This quick example of convergent evolution is great because students are likely to come across it regularly outside the lesson. If two of them go to a café and one has tea and the other a coffee, they are consuming drinks from two species that diverged about 108 million years ago and yet both evolved to produce caffeine. If a student has a coffee and a chocolate bar the two species diverged about 120 million years ago and yet they both evolved to produce caffeine – incredible!

If there’s time in the lesson, or if students ask more about it, there’s much more to the story as well. For instance, how do we know it is convergent evolution? Figure 2 in their paper is a great summary showing caffeine production mapped onto a phylogeny along with intermediates in the metabolic pathway to make caffeine and the enzymes involved. The phylogeny shows the most likely explanation is convergent evolution, the intermediates show that some of the plants use different metabolic pathways to produce the caffeine and the enzyme information shows that even species that use the same metabolic pathway use different enzymes.

More ideas…

Hopefully this blog has given you a flavour of how plant-based examples can be used to enrich A Level Biology teaching.

Please browse the spreadsheet of ideas on the SAPS website to see what sparks your interest. The ideas range from fully resourced activities to fascinating nuggets of information to drop into lessons or develop into activities yourself.

If you have other ideas that you are happy for me to include in the spreadsheet then please let me know at cgraham@hillsroad.ac.uk.

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About the author

Chris Graham has been teaching in sixth form colleges for nearly 20 years and is currently the Head of Biology at Hills Road Sixth Form College in Cambridge. He is also seconded for one day a week to Science and Plants for Schools (SAPS), working on a project to support the teaching of biology through plants. He studied Biological sciences as an undergraduate at Oxford University and then a PhD in insect neuroanatomy at Cambridge University. He is passionate about sustainability and natural history and has a particular passion for mosses and liverworts. In the school holidays you’ll find him enjoying the birds, pine woods and sea air on the north Norfolk coast with his family.