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When a Whale Falls: Matter and Energy on the Deep Seafloor

Grade 7 life science: use a museum whale-fall exhibit, a food chain energy model and scavenger data to show how matter cycles and energy flows.

Grade 7ScienceInteractive · Printable

Aligned toMS-LS2-3

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Single worksheet
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1 NGSS standard
Printable answer key
10 questions
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Details

Format: Interactive · Printable
Grade: Grade 7
Subject: Science
Question types: Fill in the blank, Multiple choice, Circle the answer, Sorting, Short answer

About this worksheet

What students practice

Students model how matter moves among producers, consumers and decomposers in an ocean ecosystem.
Students use data to explain why energy flows through an ecosystem instead of cycling.

How to use

Read the passage together and sketch the food chain on the board, then have students answer on their own. Discuss the last question as a class to separate what cycles from what flows.

Curriculum

NGSS standard covered

MS-LS2-3

Model how matter cycles and energy flows among producers, consumers and decomposers in an ecosystem.

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When a Whale Falls: Matter and Energy on the Deep Seafloor

Use a museum exhibit's model to trace matter and energy from the surface to the seafloor.

From sunlight to whale

Read the passage and study Table 1. Then answer the questions.

When a Whale Falls

1In the fossil hall of the Bayview Museum of Natural History, a 12 m fossil whale skeleton hangs above a new exhibit called When a Whale Falls. Beside the skeleton, a screen plays video from a robot camera that rested on the deep seafloor about 1,500 m below the surface, where no sunlight reaches. Museum educator Rosalind Achebe walked a seventh-grade class through the exhibit.

2The story starts in the sunlit surface water. Tiny drifting algae called phytoplankton use energy from sunlight to make sugars from carbon dioxide and water. Krill, small shrimp-like animals, eat the phytoplankton, and humpback whales eat huge amounts of krill and small fish. An adult humpback can grow to about 30,000 kg, and nearly all of that body was built from matter in the food it ate. A panel shows a simple model of how much energy reaches each level of this food chain in one year (Table 1).

3When a whale dies, its body may sink to the seafloor. The video follows one 30,000 kg humpback that landed there. Within days, hagfish, sleeper sharks and crabs arrived and began tearing off flesh and blubber. The exhibit's model estimates how much soft tissue was left over the next two years (Table 2).

4After the scavengers left, bacteria and bone-eating worms moved into the bones, which are rich in fats. Bacteria in the bones and in the mud below break down fats and other remains. As they do, they release carbon dioxide and nutrients such as nitrogen and phosphorus into the water. Scientists estimate that a large whale's bones can feed this community for decades. Every organism in the exhibit uses some of the energy in its food to move, grow and stay alive, and its body gives off heat as it does. In some places, very slow ocean currents carry nutrient-rich deep water back up toward the surface.

Table 1. Energy reaching each level in one year (model)
Level	Energy (kJ per m²)
Phytoplankton	20,000
Krill	2,000
Humpback whales	200

Each arrow below could be part of a model of this ecosystem. Sort each arrow by what moves along it.

Sunlight → phytoplanktonKrill → humpback whaleWhale blubber → hagfishBody heat from a crab → seawaterBacteria in the bones → nutrients in the waterCarbon dioxide in surface water → phytoplankton