Tidal systems with two nearly equal high and low tides daily are...
- Mixed
- Semi-diurnal
- Equinoctial
- Diurnal
Explanation: Semi-diurnal tides occur twice a day with the same height, common in the Atlantic Ocean.
Atolls often develop around a central body of water called a...
Explanation: The lagoon in an atoll is formed as the central volcanic island sinks completely beneath the sea.
What is the optimal salinity range (ppt) required for healthy coral growth?
- 5-10 ppt
- 27-30 ppt
- 40-50 ppt
- 10-15 ppt
Explanation: Corals are sensitive to salinity; they cannot survive in fresh water or extremely hypersaline conditions.
Consider: 1. Tides assist in clearing sediments from river estuaries. 2. High tides facilitate navigation into shallow-water ports.
- 1 only
- 2 only
- Both 1 and 2
- Neither 1 nor 2
Explanation: Tides act as natural desilting agents in estuaries and increase water depth in ports like Kolkata, aiding large ship movement.
What is the calcium carbonate structure secreted by coral polyps called?
- Spicule
- Exoskeleton
- Corallite
- Carapace
Explanation: Each individual polyp secretes a cup-shaped skeleton of calcium carbonate called a corallite.
A reef separated from the coast by a shallow lagoon is a...
- Atoll
- Barrier reef
- Fringing reef
- Guyot
Explanation: Barrier reefs run parallel to the shore but are separated from it by a lagoon.
Consider: 1. Corals thrive in cold, deep waters. 2. They require high turbidity for nutrient absorption.
- 1 only
- 2 only
- Both 1 and 2
- Neither 1 nor 2
Explanation: Reef-building corals require warm (20-27°C), shallow, and clear (low turbidity) water for photosynthesis by zooxanthellae.
The time period between a high tide and the following low tide is an...
- Flood tide
- Neap tide
- Spring tide
- Ebb tide
Explanation: Ebb tide is the outgoing phase where the water level falls and flows away from the coast.
Which theory explains coral reef formation as a result of sea-level changes during the Ice Age?
- Plate tectonics
- Subsidence theory
- Glacial control
- Continental drift
Explanation: Proposed by R.A. Daly, this theory emphasizes the role of sea-level fall and rise during glacial and interglacial periods.
Which force is relatively stronger in its tidal effect on Earth?
- Lunar gravity
- Solar gravity
- Friction
- Earth's gravity
Explanation: Because the Moon is much closer, its tidal-generating force is more than double that of the Sun.
In a 'Neap Tide', the gravitational pull of the Sun...
- Opposes the Moon
- Is zero
- Adds to Moon
- Doubles the Moon
Explanation: During neap tides, the Sun's pull acts at a right angle to the Moon's, partially canceling the tidal force.
Which of these is a non-climatic, biological threat to the Great Barrier Reef?
- Cyclones
- Crown-of-thorns starfish
- Centrifugal force
- Tidal bores
Explanation: Outbreaks of these coral-eating starfish can devastate large areas of healthy reef systems.
Which country is part of the mega-diverse 'Coral Triangle'?
- Indonesia
- Egypt
- India
- Brazil
Explanation: Indonesia, Philippines, Papua New Guinea, and others form the Coral Triangle, the epicenter of marine life.
When the Sun and Moon are in 'Quadrature', we experience...
- Apogean tides
- Spring tides
- Perigean tides
- Neap tides
Explanation: Quadrature means the Sun and Moon's gravitational pulls partially cancel each other out, leading to lower tidal ranges.
What is the vertical difference between high tide and low tide called?
- Tidal period
- Tidal surge
- Tidal datum
- Tidal range
Explanation: Tidal range varies geographically based on the shape of the coastline and the ocean floor.
How many high tides generally occur at a place in 24 hours in a diurnal tidal system?
Explanation: Diurnal tides consist of only one high tide and one low tide in a lunar day.
The Great Barrier Reef is primarily composed of which organism?
- Hard corals
- Mangrove roots
- Sponge colonies
- Kelp forests
Explanation: Hard (scleractinian) corals are the primary builders of the massive reef structures found in the Pacific.
Which reef system is a UNESCO World Heritage site in India?
- Malvan reef
- Gulf of Kutch
- Gulf of Mannar
- Netrani island
Explanation: The Gulf of Mannar Biosphere Reserve is a protected area known for its rich coral and seagrass ecosystems.
Mixed tides, having two highs of different heights, are common in the...
- Arctic Ocean
- Atlantic Ocean
- Pacific Ocean
- Mediterranean Sea
Explanation: The Pacific coast of North America and many Pacific islands experience mixed semi-diurnal tides.
Tides that occur during the 'Equinoxes' tend to be...
- Diurnal only
- Very high
- Mixed only
- Very low
Explanation: Equinoctial spring tides occur when the sun is directly over the equator, maximizing the combined pull.
When the Moon is at its closest point to Earth, the resulting higher tides are called...
- Apogean tides
- Equinoctial tides
- Perigean tides
- Solstice tides
Explanation: Perigee is the point where the Moon is closest to Earth, resulting in a stronger gravitational pull and higher tides.
Which of the following is a major threat to coral reefs globally?
- High salinity
- Centrifugal force
- Ocean acidification
- Low tides
Explanation: Higher CO2 levels make the ocean more acidic, making it harder for corals to build their calcium carbonate skeletons.
What is the primary chemical compound that forms a coral reef's structure?
- Calcium carbonate
- Magnesium sulfate
- Silicon dioxide
- Sodium chloride
Explanation: Coral polyps extract calcium ions and carbonates from seawater to build their hard stony skeletons.
The 'Subsidence Theory' regarding the origin of atolls was proposed by...
- Arthur Holmes
- Charles Darwin
- Reginald Daly
- Harry Hess
Explanation: Darwin's theory suggests atolls form as volcanic islands slowly sink while coral continues to grow upward.
What happens to the magnitude of tides when the Earth is at 'Perihelion'?
- Tides are lower
- No effect
- Only one tide
- Tides are higher
Explanation: At perihelion (closest to the Sun), the solar tidal force is at its maximum, leading to slightly larger tidal ranges.
The largest barrier reef system in the world is located off the coast of...
- India
- Australia
- Belize
- Brazil
Explanation: The Great Barrier Reef off the coast of Queensland, Australia, is the world's largest coral reef system.
Consider: 1. Coral reefs are called 'Rainforests of the Ocean'. 2. The 'Coral Triangle' is located in the North Atlantic.
- 2 only
- 1 only
- Both 1 and 2
- Neither 1 nor 2
Explanation: Corals support immense biodiversity like rainforests; however, the Coral Triangle is in the western Pacific (Indo-Pacific).
The area between the highest high tide and lowest low tide marks is the...
- Intertidal zone
- Benthic zone
- Abyssal zone
- Pelagic zone
Explanation: Also called the littoral zone, it is the area exposed to air at low tide and submerged at high tide.
The symbiotic algae that live within coral tissues and provide nutrients are called...
- Sargassum
- Kelp
- Zooxanthellae
- Phytoplankton
Explanation: Zooxanthellae perform photosynthesis and provide oxygen and nutrients to the coral polyps.
Corals cannot grow near the mouths of large rivers primarily because of...
- Freshwater inflow
- Fast currents
- Deep water
- High temperature
Explanation: Large rivers discharge fresh water and silt, which lowers salinity and chokes the polyps, preventing coral growth.
The relationship between coral polyps and zooxanthellae is an example of...
- Commensalism
- Predation
- Mutualism
- Parasitism
Explanation: Both organisms benefit: the coral gets nutrients/oxygen, and the algae get a protected environment and CO2.
Points in the ocean where there is zero tidal amplitude are called...
- Cotidal points
- Nodal points
- Amphidromic points
- Zenith points
Explanation: Amphidromic points are 'no-tide' points around which the tidal crest rotates.
Which specific reef type is often associated with a 'Sunken Volcano'?
- Fringing reef
- Atoll
- Cuesta
- Barrier reef
Explanation: Atolls form as coral continues to grow upward around a volcanic island that has subsided or eroded away.
The incoming 'Tidal Bore' in the Hooghly River is dangerous for...
- Deep-sea fish
- Small boats
- Coral reefs
- Large tankers
Explanation: The sudden surge of water can easily capsize small vessels and disrupt river navigation.
Tides that occur during the Moon's 'Apogee' (furthest point) are...
- Exceptionally high
- Lower than average
- Higher than average
- Twice a day
Explanation: When the Moon is at apogee, its gravitational pull is at its weakest, resulting in smaller tidal ranges.
Which of these Indian regions is completely devoid of coral reefs?
- Gulf of Kutch
- Andaman Islands
- Lakshadweep Islands
- Gulf of Khambhat
Explanation: High turbidity and freshwater discharge from major rivers like Narmada and Tapti prevent coral growth in the Gulf of Khambhat.
Corals are predominantly found between which latitudes?
- 60°N and 60°S
- 45°N and 45°S
- Equator only
- 30°N and 30°S
Explanation: Corals are tropical and subtropical organisms, limited by the 20°C isotherm which usually falls within these latitudes.
The time between high and low tide when the water is stationary is...
- Ebb
- Slack water
- Flood
- Bore
Explanation: Slack water occurs at the peak or trough of a tide when the horizontal tidal current stops before reversing.
The process where rising tide water moves into a bay or estuary is called...
- Slack water
- Ebb tide
- Tidal range
- Flood tide
Explanation: Flood tide is the incoming tide phase where water moves toward the shore and up into estuaries.
What is the maximum depth (meters) generally suitable for reef-building corals?
- 10-20 meters
- 200-300 meters
- 500-1000 meters
- 45-50 meters
Explanation: While some exist deeper, the majority of reef-building corals are found above 50 meters to ensure adequate light.
A lunar day, which determines the timing of tides, is approximately...
- 25.5 hours
- 24 hours
- 12 hours
- 24.8 hours
Explanation: A lunar day is the time it takes for a point on Earth to return to the same position relative to the moon.
Most of the islands in the Lakshadweep archipelago are classified as...
- Volcanic islands
- Barrier islands
- Atolls
- Continental islands
Explanation: Lakshadweep islands are primarily coral atolls built on the submerged Laccadive-Chagos ridge.
Why are reef-building corals generally restricted to the 'Euphotic zone'?
- High pressure
- Need for light
- Warm currents
- Low salinity
Explanation: The symbiotic zooxanthellae require sunlight for photosynthesis, limiting reef growth to shallow, clear waters.
In India, the Gulf of Mannar is famous for which type of coral reef?
- Barrier reef
- Patch reef
- Fringing reef
- Atoll
Explanation: The reefs in the Gulf of Mannar and the Palk Bay are predominantly fringing reefs.
Which ocean has the most extensive distribution of coral reefs?
- Atlantic Ocean
- Pacific Ocean
- Arctic Ocean
- Indian Ocean
Explanation: The Pacific Ocean, particularly the Indo-Pacific region, contains the vast majority of the world's coral reefs.
What is the typical time interval between two high tides in a semi-diurnal system?
- 24 hours 50m
- 12 hours
- 12 hours 25m
- 6 hours
Explanation: Because the Moon revolves around the Earth, a complete tidal cycle (two highs and two lows) takes 24 hours and 50 minutes.
The rise in sea level that accompanies a cyclone and affects tidal height is a...
- Neap tide
- Spring tide
- Tidal bore
- Storm surge
Explanation: While not a tide, a storm surge can coincide with high tide to cause catastrophic coastal flooding.
A coral reef that grows directly from the shoreline is called a...
- Barrier reef
- Fringing reef
- Atoll
- Platform reef
Explanation: Fringing reefs are the most common type and extend seaward directly from the coast without a lagoon.
The 'Ebb tide' refers to...
- Lowest tide
- Highest tide
- Rising tide
- Falling tide
Explanation: The period between high tide and low tide during which water flows away from the shore is called the ebb.
Which force, along with lunar gravity, is primarily responsible for creating tidal bulges?
- Frictional force
- Coriolis force
- Magnetic force
- Centrifugal force
Explanation: Tides are caused by the imbalance between the Moon's gravitational pull and the centrifugal force of the Earth-Moon system.
Which Indian gulf is considered a high-potential area for tidal energy generation?
- Gulf of Khambhat
- Gulf of Eden
- Gulf of Oman
- Gulf of Mannar
Explanation: The Gulf of Khambhat and Gulf of Kutch in Gujarat have very high tidal ranges suitable for energy production.
Which type of coral reef is separated from the mainland by a deep lagoon?
- Barrier reef
- Atoll
- Patch reef
- Fringing reef
Explanation: Barrier reefs run parallel to the shore but are separated by a wide, deep channel or lagoon.
Large-scale coral spawning events usually happen in response to...
- Magnetic storms
- Solar eclipses
- Lunar cycles
- Tectonic shifts
Explanation: Mass spawning is often triggered by water temperature and the phases of the moon to maximize fertilization.
The alignment of the Sun, Moon, and Earth in a straight line is technically known as...
- Syzygy
- Perigee
- Apogee
- Quadrature
Explanation: Syzygy refers to the straight-line configuration of three celestial bodies; in this context, it causes Spring tides.
Consider: 1. Spring tides occur during New Moon and Full Moon. 2. Neap tides occur when the Sun and Moon are at right angles.
- 2 only
- 1 only
- Both 1 and 2
- Neither 1 nor 2
Explanation: Spring tides happen when the Sun, Moon, and Earth are aligned (Syzygy); Neap tides occur during the first and third quarters (Quadrature).
Coral bleaching is primarily caused by an increase in...
- Ocean depth
- Water temperature
- Water salinity
- Tidal speed
Explanation: When water is too warm, corals expel the zooxanthellae living in their tissues, causing them to turn completely white.
A wall of water that moves up certain rivers during an incoming tide is called a...
- Storm surge
- Tsunami
- Tidal wave
- Tidal bore
Explanation: Tidal bores occur in rivers with narrow estuaries and high tidal ranges, such as the Hooghly or the Amazon.
What is the effect of heavy sedimentation on coral reefs?
- Accelerates growth
- Provides nutrients
- Increases salinity
- Smothers polyps
Explanation: Sediments settle on corals, blocking light and physically choking the polyps, leading to reef death.
How does ocean acidification affect coral reefs?
- Increases light
- Warms the water
- Adds nutrients
- Weakens skeletons
Explanation: Lower pH levels reduce the availability of carbonate ions, making it harder for corals to calcify.
Which of the following locations is famous for experiencing the world's highest tidal range?
- Bay of Bengal
- Bay of Fundy
- Hudson Bay
- Gulf of Mexico
Explanation: The Bay of Fundy in Canada experiences tidal ranges of up to 16 meters due to its unique funnel shape.