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📌 The Question:

Which of the following have species that can establish symbiotic relationships with other organisms?

1. Cnidarians
2. Fungi
3. Protozoa

Select the correct answer using the code given below:

(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3

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✅ Correct Answer: (d) 1, 2 and 3

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🧠 Classroom Explanation:

All three groups listed are well known for forming symbiotic relationships.

🔹 Cnidarians ✔️
Cnidarians (corals, sea anemones, hydra, jellyfish) commonly form mutualistic symbiosis with dinoflagellate algae (zooxanthellae).
• Algae provide food via photosynthesis
• Cnidarians provide shelter and nutrients
This relationship is foundational to coral reef ecosystems.

🔹 Fungi ✔️
Fungi are masters of symbiosis:
• Mycorrhiza → fungi + plant roots (nutrient exchange)
• Lichens → fungi + algae/cyanobacteria
These partnerships enhance nutrient absorption, soil health, and ecological resilience.

🔹 Protozoa ✔️
Protozoa often live in mutualistic association with animals.
• Classic example: Protozoa in termite guts
• They help digest cellulose, allowing termites to survive on wood
Without protozoa, termites would starve.

Hence, all three organisms exhibit symbiotic species.

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🔍 Curiosity Raiser:
🌍 Did you know?
Coral reefs exist only because of symbiosis. Without microscopic algae living inside corals, entire reef ecosystems would collapse.

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📚 Enrich Notes (Prelims Value-Add):

• Symbiosis Types you must recall:

• Mutualism (both benefit)
• Commensalism (one benefits, other unaffected)
• Parasitism (one benefits, other harmed)

• High-Probability Exam Areas:

• Coral bleaching = breakdown of cnidarian–algae symbiosis
• Mycorrhiza = soil fertility + sustainable agriculture

• UPSC Trick:

• If fungi appear with “mutualism / lichen / roots” → usually correct

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🪶 IAS Monk Whisper:
Life rarely survives alone — nature thrives through alliances.