Q1. Which of the following types of corals are responsible for reef building?
- Soft corals
- Hard corals
- Cold water corals
- Zooxanthellae
Correct Option: 2. Hard corals
Explanation: Only hard corals (also known as hermatypic corals) secrete calcium carbonate skeletons, which build up over time to form coral reefs. Soft corals like sea fans do not contribute to reef structure.
Q2. Coral polyps share a symbiotic relationship with which of the following?
- Bacteria
- Diatoms
- Zooxanthellae
- Sea grass
Correct Option: 3. Zooxanthellae
Explanation: Coral polyps live in symbiosis with zooxanthellae, microscopic algae that live within their tissues. The algae provide energy to the corals via photosynthesis, while corals provide a safe habitat and CO₂ for the algae.
Q3. Coral reefs are commonly referred to as:
- Deserts of the sea
- Ocean’s lungs
- Tropical Rainforests of the Oceans
- Grasslands of the ocean
Correct Option: 3. Tropical Rainforests of the Oceans
Explanation: Due to their high biodiversity and complex ecosystems, coral reefs are often referred to as the “Tropical Rainforests of the Oceans.”
Q4. Which of the following reef types is circular and surrounds a lagoon?
- Patch reef
- Fringing reef
- Barrier reef
- Atoll
Correct Option: 4. Atoll
Explanation: An atoll is a circular or semi-circular reef that forms around a lagoon, usually over a subsiding seafloor where the coral growth keeps pace with the sinking.
Q5. Coral bleaching is primarily caused by:
- Elevated sea temperatures
- Increase in fish population
- Excess sedimentation
- High ocean salinity
Correct Option: 1. Elevated sea temperatures
Explanation: The primary cause of coral bleaching is high sea surface temperatures. When water is too warm, corals expel their zooxanthellae, leading to loss of color and energy.