▶️ Answer/Explanation
Detailed Solution
a.
- The interaction between Zooxanthellae and reef-building corals is mutualism, where both organisms benefit: corals provide shelter and nutrients, while Zooxanthellae supply energy through photosynthesis.
b.
- Zooxanthellae are producers as they perform photosynthesis, creating energy-rich compounds from sunlight.
c.
- Organisms like Gorgonia, Diadema, algae, and sponges that indicate specific environmental conditions (e.g., coral bleaching) are called indicator species.
d.
- Eutrophication is the nutrient enrichment of water, often with nitrates or phosphates from agricultural runoff or sewage.
- These nutrients act as fertilizers, promoting excessive algal growth by providing the resources needed for rapid proliferation.
e.
- Top-down factors involve predation or herbivory that control lower trophic levels, limiting algal overgrowth.
- For example, parrotfish (a herbivorous predator) graze on algae, reducing their population and preventing them from smothering coral reefs.
Markscheme
a. Interaction Between Zooxanthellae and Corals: [1]
symbiosis/mutualism ✔
b. Trophic Level of Zooxanthellae: [1]
producers ✔
c. Term for Organisms Indicating Environmental Conditions: [1]
indicator species ✔
d. Relationship Between Eutrophication and Algal Growth: [2]
a. eutrophication is nutrient enrichment of a body of water ✔
b. example of nutrients eg: nitrates ✔
c. «nutrients» serve as fertilizer for the algae «promoting growth» ✔
e. Top-Down Control of Algal Growth: [2]
a. top-down factors refer to predation/herbivory/trophic level above another one ✔
b. which limit/control population growth ✔
c. named example of a top-down predator eg: parrotfish. Do not accept general names, like “fish” ✔