How Corals Capture Sunlight
Corals are animals that get most of their energy from microscopic algae living inside them; those algae capture sunlight and turn it into sugar.
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Start when you are ready to enter this Stage's 9 scenes and explore, respond, and learn as you go.
How can an animal get energy from sunlight?
- coral-animal
- Corals are colonial animals, not plants; each small polyp catches plankton with tentacles.
- photosynthesis
- The process by which algae use sunlight, water, and carbon dioxide to make sugar and oxygen.
- zooxanthellae
- Microscopic algae that live inside coral tissues and carry out photosynthesis.
- symbiosis
- A close partnership where coral and algae exchange nutrients; this one is mutualistic because both partners benefit.
- sunlight-in-ocean
- Sunlight fades quickly with depth and water cloudiness, limiting where photosynthetic corals can live.
- coral-bleaching
- A stress response in which corals expel their algae and lose their main food source.
Corals are plants because they use sunlight to make food.
Clarify that corals are animals; the photosynthetic partner is algae living inside them.
Corals photosynthesize by themselves.
Show that zooxanthellae, not coral cells, perform photosynthesis.
Corals can capture sunlight no matter how deep they live.
Connect light penetration to depth and explain why reef-building corals need shallow, clear water.
- detailed chemistry of photosynthesis
- coral reproduction
- reef calcification chemistry
- deep-sea coral communities
- Learner explains that corals are animals with algae partners.
- Learner identifies zooxanthellae as the photosynthesizers.
- Learner gives a reason why reef-building corals live in shallow, clear water.
- At a beach, aquarium, or reef photo, recognize why corals need sunlight and what happens if they lose their algae.
General learners curious about ocean life; no biology background required.
- 01A Sunlit MysteryslideOrientationObserve
Open with the puzzle: corals look like plants or rocks, yet they are animals that depend on sunlight.
- Corals look like colorful plants or rocks—but they are animals.
- The biggest reefs grow in warm, shallow, sunlit water.
- We will trace how sunlight becomes energy for a coral animal.
- 02What Do You Think Corals Are?quizPredictionPredict
Before the explanation, learners commit to a guess about whether corals are plants or animals.
- Choose your current idea about corals.
- 03Corals Are Animals with TentaclesslideModel buildingObserve
Introduce coral animal biology: tiny polyps, stinging tentacles, and catching plankton.
- Each coral is a colony of tiny animals called polyps.
- Polyps use stinging tentacles to catch plankton.
- Plankton meals alone do not explain how huge reefs are built.
- 04Dive Into the Sunlit ZoneinteractivePredictionPredict
Learners predict how light disappears with depth, then explore an interactive depth slider to see why reef corals stay shallow.
- Guess how much sunlight reaches 10 m, 30 m, and deeper.
- Drag to dive and watch light intensity drop.
- Most reef-building corals need clear, shallow water near the surface.
- 05The Secret: Algae Living InsideslideMisconception repairObserve
Reveal the zooxanthellae – microscopic algae that live inside coral tissues and do the photosynthesis.
- Inside each coral polyp live millions of microscopic algae called zooxanthellae.
- The algae absorb sunlight and use it to make sugars.
- The coral receives most of its energy from those sugars.
- 06A Win-Win PartnershipslideModel buildingObserve
Explain mutualistic symbiosis: what the algae gain from the coral and what the coral gains from the algae.
- Coral gives algae shelter, nutrients, and carbon dioxide.
- Algae give coral oxygen and sugar from photosynthesis.
- This relationship is called mutualistic symbiosis.
- 07Check the PartnershipquizAssessmentChoose
A quick knowledge check on who photosynthesizes and why corals live in shallow water.
- Identify the photosynthesizer inside a coral.
- Apply the light-depth idea to reef locations.
- 08Apply It: Why Heat Harms CoralsquizApplicationExplain
Use the symbiotic model to explain what happens when warm water makes corals expel their algae.
- Answer in your own words why a bleached coral can starve even in bright sunlight.
- 09From Sunlight to ReefslideSynthesisObserve
Bring the full story together with the energy flow: sunlight, algae, sugar, coral, and reef growth.
- Sunlight reaches shallow, clear water.
- Zooxanthellae capture it and make sugar.
- That sugar powers the coral colony and supports a whole reef ecosystem.
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