A No-Prep Sub Plan for Photosynthesis (Cambridge IGCSE)

You are out on Thursday, the cover teacher trained in modern languages, and your Cambridge IGCSE group is halfway through photosynthesis. The plan below is built for that exact situation: no practical equipment, no subject knowledge required from the adult in the room, a clear sequence of instructions, and a piece of written work you can collect and use. It fills a sixty-minute lesson and leaves the scheme of work where you left it.

What a cover teacher needs from you

Cover lessons fail for predictable reasons. The instructions assume knowledge the adult does not have, the task finishes in twenty minutes, or nothing is collected so nothing was at stake. Write the plan so that every instruction is executable by someone who does not know what a chloroplast is, put timings on it, and make the final product something you will visibly act on next lesson. Say so on the sheet: your teacher will mark section three. That one line changes the effort level in a cover lesson more than any behaviour system.

The lesson, minute by minute

1. 0–5, settle and set. Students copy the equation for photosynthesis from the board into their books. The cover teacher does not need to explain it; the instruction is to copy it accurately, including the conditions above and below the arrow.
2. 5–15, the reading. A one-page text on how a leaf is built for its job. Students read it twice: once straight through, once with a pencil underlining any word they cannot define. The second reading is the one that matters.
3. 15–30, the labelled diagram. A cross-section of a leaf with eight labels supplied in a box and the instruction to place each one and add a short reason it belongs there. The reason is what turns a copying exercise into thinking.
4. 30–45, the six questions. Graded from recall to application, with the last question asking what would happen to a plant kept in blue light only. Every question is answerable from the reading, so the cover teacher never has to explain anything.
5. 45–55, the paragraph. Using the command word explain, students write one paragraph on why a plant kept in the dark eventually dies. This is section three, the piece you collect.
6. 55–60, hand in and stack. Books closed, sheets stacked on your desk, room tidy. Give the cover teacher a script for this so it happens.

Building all of that from scratch on the morning you wake up ill is not realistic, which is the argument for keeping a finished version in the drawer. Photosynthesis and Plant Metabolism | Leaf Structure, Chloroplasts & the Calvin Cycle contains the reading, the diagram and the graded questions in printable form with full answer keys, so the whole sequence above can be assembled once and reused every year.

Adjusting for the group you actually have

Two versions of the question set solve most problems. The scaffolded version supplies the first three words of each answer; the standard version does not. Print both, tell the cover teacher that students may take either, and the differentiation happens without anyone having to judge a class they have never met. For a group with a strong reading age, add a single extension question about limiting factors and let it run.

If the cover is longer than one lesson, you need a second and third lesson that do not depend on the first. Drawing them from a wide unit avoids repetition: High School Biology Mega Bundle – Evolution, Ecology, Photosynthesis, Climate Change & Animal Behavior covers enough adjacent ground that a three-day absence can be planned in one sitting, with each day self-contained.

What you do with the work when you are back

Read the paragraphs first, not the diagrams. They tell you whether the class understood that photosynthesis makes food rather than makes air, which is the misconception that outlives every lesson on this topic. Open your return lesson by projecting two anonymous paragraphs, one strong and one muddled, and having the class improve the second. That takes eight minutes and makes the cover lesson part of the sequence rather than a hole in it.

Keeping a standing emergency folder is the real lesson here. A broad set such as Ultimate Biology Teaching Bundle 🌍 Life Science, Plants, Animals, Ecology, Genetics & Cells | Grades 5–10 gives you cover-ready material across the biology strand, so the next unplanned absence costs you one email rather than an evening. Do that once and the day you wake up unable to teach stops being a day your class loses.

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