Explore sunlit and deep ocean zones, spring and neap tides, phytoplankton and coral reef protection. Review suitability for your learners before teaching.
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Worksheet StudioPractice pack · Ages 7-9
Ocean zones, tides & marine life
Take your time. Show your thinking.
1. What causes the regular twice-daily rise and fall of sea level (the tides) along coastlines: the gravitational pull of the Moon and the Sun, or underwater volcanoes?
What causes the regular tw… · Ocean zones, tides & marin…
2. What symbiotic microscopic algae live inside reef-building coral polyps and provide them with food via photosynthesis: zooxanthellae or mosses?
What symbiotic microscopic… · Ocean zones, tides & marin…
3. What is the deepest known trench in Earth’s oceans, located in the western Pacific Ocean: the Mariana Trench or the Grand Canyon?
What is the deepest known … · Ocean zones, tides & marin…
4. What are the superheated mineral-rich chimneys on the deep ocean floor along mid-ocean ridges that support chemosynthetic life without sunlight: hydrothermal vents or sand dunes?
What are the superheated m… · Ocean zones, tides & marin…
5. What is the average salinity (dissolved salt content) of open ocean water: about 3.5% (35 parts per thousand) or 50%?
3.5% · 35 · 50% · Ocean zones, tides & marin…
6. What is the shallow, gently sloping submerged edge of a continent before the seafloor drops steeply into the deep ocean: the continental shelf or an ocean trench?
What is the shallow, gentl… · Ocean zones, tides & marin…
7. What happens during “coral bleaching” when sea temperatures stay abnormally high for too long: corals expel their symbiotic algae and turn white, or corals turn into granite?
“coral bleaching” · Ocean zones, tides & marin…
8. How do underwater seagrass meadows help protect tropical lagoons and climate: they trap sediment, shelter juvenile fish and store carbon, or they make the water salty?
How do underwater seagrass… · Ocean zones, tides & marin…
9. Which top layer of the ocean (from the surface down to about 200 m) receives enough sunlight for photosynthesis: the sunlight (euphotic) zone or the midnight zone?
200 m · Ocean zones, tides & marin…
10. What are the microscopic drifting algae near the ocean surface that perform photosynthesis and produce much of Earth’s oxygen: phytoplankton or stalactites?
What are the microscopic d… · Ocean zones, tides & marin…
11. How does a healthy barrier or fringing coral reef protect low-lying islands during storms: it dissipates most of the incoming wave energy before waves reach the shore, or it stops the wind?
How does a healthy barrier… · Ocean zones, tides & marin…
12. Which dissolved compound makes up the largest share of salt in seawater: sodium chloride (NaCl) or sucrose?
Which dissolved compound m… · Ocean zones, tides & marin…
12 questions · Seed 43 · Age guidance, not curriculum certification
View the answer key
Worksheet StudioAnswer key · Ages 7-9
Ocean zones, tides & marine life
Answers and reasoning. Review before teaching.
1. What causes the regular twice-daily rise and fall of sea level (the tides) along coastlines: the gravitational pull of the Moon and the Sun, or underwater volcanoes?
The gravitational pull of the Moon and the Sun
Gravitational attraction from the Moon (and Sun) creates tidal bulges in Earth’s oceans.
2. What symbiotic microscopic algae live inside reef-building coral polyps and provide them with food via photosynthesis: zooxanthellae or mosses?
Zooxanthellae
Corals depend on photosynthetic zooxanthellae for up to 90% of their energy.
3. What is the deepest known trench in Earth’s oceans, located in the western Pacific Ocean: the Mariana Trench or the Grand Canyon?
Mariana Trench
The Mariana Trench reaches nearly 11,000 metres below sea level.
4. What are the superheated mineral-rich chimneys on the deep ocean floor along mid-ocean ridges that support chemosynthetic life without sunlight: hydrothermal vents or sand dunes?
Hydrothermal vents
Bacteria at hydrothermal vents use chemical energy from hydrogen sulfide (chemosynthesis) instead of sunlight.
5. What is the average salinity (dissolved salt content) of open ocean water: about 3.5% (35 parts per thousand) or 50%?
About 3.5% (35 parts per thousand)
One kilogram of typical seawater contains about 35 grams of dissolved salts, mostly sodium chloride.
6. What is the shallow, gently sloping submerged edge of a continent before the seafloor drops steeply into the deep ocean: the continental shelf or an ocean trench?
Continental shelf
Continental shelves are nutrient-rich shallow seas bordering continents.
7. What happens during “coral bleaching” when sea temperatures stay abnormally high for too long: corals expel their symbiotic algae and turn white, or corals turn into granite?
Corals expel their symbiotic algae and turn white
Thermal stress causes corals to expel zooxanthellae, exposing their white calcium carbonate skeleton.
8. How do underwater seagrass meadows help protect tropical lagoons and climate: they trap sediment, shelter juvenile fish and store carbon, or they make the water salty?
They trap sediment, shelter juvenile fish and store carbon
Seagrasses are flowering marine plants that stabilise lagoon beds and sequester “blue carbon”.
9. Which top layer of the ocean (from the surface down to about 200 m) receives enough sunlight for photosynthesis: the sunlight (euphotic) zone or the midnight zone?
Sunlight (euphotic) zone
Most marine plants, phytoplankton and coral reefs live in the sunlit euphotic zone.
10. What are the microscopic drifting algae near the ocean surface that perform photosynthesis and produce much of Earth’s oxygen: phytoplankton or stalactites?
Phytoplankton
Phytoplankton form the primary producer base of most ocean food webs.
11. How does a healthy barrier or fringing coral reef protect low-lying islands during storms: it dissipates most of the incoming wave energy before waves reach the shore, or it stops the wind?
It dissipates most of the incoming wave energy before waves reach the shore
12. Which dissolved compound makes up the largest share of salt in seawater: sodium chloride (NaCl) or sucrose?
Sodium chloride (NaCl)
Sodium (Na⁺) and chloride (Cl⁻) ions account for over 85% of dissolved solids in seawater.
12 questions · Seed 43 · Age guidance, not curriculum certification
Worksheet StudioPractice pack · Ages 7-9
Ocean zones, tides & marine life
Take your time. Show your thinking.
1. What causes the regular twice-daily rise and fall of sea level (the tides) along coastlines: the gravitational pull of the Moon and the Sun, or underwater volcanoes?
What causes the regular tw… · Ocean zones, tides & marin…
2. What symbiotic microscopic algae live inside reef-building coral polyps and provide them with food via photosynthesis: zooxanthellae or mosses?
What symbiotic microscopic… · Ocean zones, tides & marin…
3. What is the deepest known trench in Earth’s oceans, located in the western Pacific Ocean: the Mariana Trench or the Grand Canyon?
What is the deepest known … · Ocean zones, tides & marin…
4. What are the superheated mineral-rich chimneys on the deep ocean floor along mid-ocean ridges that support chemosynthetic life without sunlight: hydrothermal vents or sand dunes?
What are the superheated m… · Ocean zones, tides & marin…
5. What is the average salinity (dissolved salt content) of open ocean water: about 3.5% (35 parts per thousand) or 50%?
3.5% · 35 · 50% · Ocean zones, tides & marin…
6. What is the shallow, gently sloping submerged edge of a continent before the seafloor drops steeply into the deep ocean: the continental shelf or an ocean trench?
What is the shallow, gentl… · Ocean zones, tides & marin…
7. What happens during “coral bleaching” when sea temperatures stay abnormally high for too long: corals expel their symbiotic algae and turn white, or corals turn into granite?
“coral bleaching” · Ocean zones, tides & marin…
8. How do underwater seagrass meadows help protect tropical lagoons and climate: they trap sediment, shelter juvenile fish and store carbon, or they make the water salty?
How do underwater seagrass… · Ocean zones, tides & marin…
9. Which top layer of the ocean (from the surface down to about 200 m) receives enough sunlight for photosynthesis: the sunlight (euphotic) zone or the midnight zone?
200 m · Ocean zones, tides & marin…
10. What are the microscopic drifting algae near the ocean surface that perform photosynthesis and produce much of Earth’s oxygen: phytoplankton or stalactites?
What are the microscopic d… · Ocean zones, tides & marin…
11. How does a healthy barrier or fringing coral reef protect low-lying islands during storms: it dissipates most of the incoming wave energy before waves reach the shore, or it stops the wind?
How does a healthy barrier… · Ocean zones, tides & marin…
12. Which dissolved compound makes up the largest share of salt in seawater: sodium chloride (NaCl) or sucrose?
Which dissolved compound m… · Ocean zones, tides & marin…
12 questions · Seed 43 · Age guidance, not curriculum certification
Worksheet StudioAnswer key · Ages 7-9
Ocean zones, tides & marine life
Answers and reasoning. Review before teaching.
1. What causes the regular twice-daily rise and fall of sea level (the tides) along coastlines: the gravitational pull of the Moon and the Sun, or underwater volcanoes?
The gravitational pull of the Moon and the Sun
Gravitational attraction from the Moon (and Sun) creates tidal bulges in Earth’s oceans.
2. What symbiotic microscopic algae live inside reef-building coral polyps and provide them with food via photosynthesis: zooxanthellae or mosses?
Zooxanthellae
Corals depend on photosynthetic zooxanthellae for up to 90% of their energy.
3. What is the deepest known trench in Earth’s oceans, located in the western Pacific Ocean: the Mariana Trench or the Grand Canyon?
Mariana Trench
The Mariana Trench reaches nearly 11,000 metres below sea level.
4. What are the superheated mineral-rich chimneys on the deep ocean floor along mid-ocean ridges that support chemosynthetic life without sunlight: hydrothermal vents or sand dunes?
Hydrothermal vents
Bacteria at hydrothermal vents use chemical energy from hydrogen sulfide (chemosynthesis) instead of sunlight.
5. What is the average salinity (dissolved salt content) of open ocean water: about 3.5% (35 parts per thousand) or 50%?
About 3.5% (35 parts per thousand)
One kilogram of typical seawater contains about 35 grams of dissolved salts, mostly sodium chloride.
6. What is the shallow, gently sloping submerged edge of a continent before the seafloor drops steeply into the deep ocean: the continental shelf or an ocean trench?
Continental shelf
Continental shelves are nutrient-rich shallow seas bordering continents.
7. What happens during “coral bleaching” when sea temperatures stay abnormally high for too long: corals expel their symbiotic algae and turn white, or corals turn into granite?
Corals expel their symbiotic algae and turn white
Thermal stress causes corals to expel zooxanthellae, exposing their white calcium carbonate skeleton.
8. How do underwater seagrass meadows help protect tropical lagoons and climate: they trap sediment, shelter juvenile fish and store carbon, or they make the water salty?
They trap sediment, shelter juvenile fish and store carbon
Seagrasses are flowering marine plants that stabilise lagoon beds and sequester “blue carbon”.
9. Which top layer of the ocean (from the surface down to about 200 m) receives enough sunlight for photosynthesis: the sunlight (euphotic) zone or the midnight zone?
Sunlight (euphotic) zone
Most marine plants, phytoplankton and coral reefs live in the sunlit euphotic zone.
10. What are the microscopic drifting algae near the ocean surface that perform photosynthesis and produce much of Earth’s oxygen: phytoplankton or stalactites?
Phytoplankton
Phytoplankton form the primary producer base of most ocean food webs.
11. How does a healthy barrier or fringing coral reef protect low-lying islands during storms: it dissipates most of the incoming wave energy before waves reach the shore, or it stops the wind?
It dissipates most of the incoming wave energy before waves reach the shore