Teacher sheet · Ages 10–11 · about 45–50 minutes
Coral reefs: partners, builders and bleaching
Lesson page: echoesof.science/school/coral-reefs/ages-10-11/ · Pupil worksheet: echoesof.science/school/coral-reefs/ages-10-11/print/
Learning aims
- Describe corals as colonial animals made of polyps that build limestone skeletons.
- Explain the partnership between corals and zooxanthellae.
- Name and describe fringing reefs, barrier reefs and atolls.
- Explain coral bleaching and why acidic water is a problem; plan a fair test.
Lesson plan
| Time | Activity |
|---|---|
| 5 min | Starter: picture of a reef from above. How could tiny animals build this? |
| 10 min | Read the text; draw the three reef types. |
| 20 min | Set up the shell fair test (results next week). |
| 5 min | Good or bad for a reef? game. |
| 5 min | Quiz. |
Materials for the experiment
- Four clean jars with lids
- White vinegar
- Water
- Carbonated (fizzy) water
- Salt
- Measuring cup and teaspoon
- 12 clean, similar clam or mussel shells
- pH test strips (optional)
- Labels, camera or drawing paper
Safety: Wear safety glasses when pouring vinegar; rinse splashes from skin or eyes with plenty of water. Do not taste any liquid. Keep the closed jars where they will not be knocked over. Wash hands after handling the shells.
Common misconceptions
| Pupils may think… | Actually… |
|---|---|
| Coral reefs are rocks. | Reefs are built by living animals; the limestone is their skeleton. |
| Bleaching means the coral is dead. | A bleached coral has lost its algae but is still alive; if stress continues it may starve and die. |
| Corals get all their food by catching it. | Most of their food comes from the algae living in their tissues. |
| Reefs grow fast. | Massive corals grow only about 0.5–2 cm a year. |
Worksheet answers
- The algae photosynthesise and give the coral most of their food (up to 90%); the coral gives the algae shelter, carbon dioxide and water.
- Fringing reef next to the shore; barrier reef with a lagoon between reef and land; atoll as a ring of reef around a lagoon.
- Changed: the liquid. Observed: how much the shells changed (and the pH). Kept the same: type and size of shells, amount of liquid, time, closed jars.
- It has pushed out its coloured algae, so we see the white skeleton through its clear tissue.
Quiz answers
- Why are corals animals and not plants? They cannot make their own food. Plants make their own food; corals catch food and get it from their algae.[1]
- What do zooxanthellae give the coral? Food made by photosynthesis. Up to 90% of the food the algae make goes to the coral.[2]
- What is a reef skeleton made of? Calcium carbonate (limestone). Polyps build limestone skeletons layer by layer.[6]
- Which kind of reef forms a ring around a lagoon? An atoll. An atoll forms where a volcanic island has sunk while the coral kept growing.[5]
- What usually causes coral bleaching? Water that stays too warm. Warm water makes corals expel their algae.[3]
- Reefs cover less than 1% of the ocean. How many ocean species live there? Nearly a quarter. Reefs are packed with life.[4]
Going further
Find the Great Barrier Reef and a Pacific atoll on a globe. Check: are they between 30° N and 30° S? Then plan a test of whether warm or cold vinegar dissolves a shell faster.
Sources used in this lesson
- [1] Is coral an animal or a plant? (NOAA National Ocean Service): reliability High
- [2] Corals tutorial: zooxanthellae… what's that? (NOAA National Ocean Service (education tutorial)): reliability High
- [3] What is coral bleaching? (NOAA National Ocean Service): reliability High
- [4] Shallow coral reef habitat (NOAA Fisheries): reliability High
- [5] What are coral reefs? (NOAA Coral Reef Information System (CoRIS)): reliability High
- [6] What are coral reefs made of? (NOAA National Ocean Service): reliability High
- [7] Disappearing shells (lesson plan) (NOAA Office of National Marine Sanctuaries): reliability High
Full list with links and a note on each source's reliability: echoesof.science/school/coral-reefs/sources/
Privacy: the lesson pages have no ads, no tracking and no cookies. Quiz answers and game scores stay in the pupil's browser. A short video for each age is coming.