182 Life in the Ocean’s Depths
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LIFE IN THE OCEAN’S
DEPTHS
Chapter Outline
SURVIVAL IN THE DEEP SEA
Adaptations to Pressure
Adaptations to Cold
LIFE IN THE DARK
Color in Deep Sea Organisms
Roles of Bioluminescence
Camouflage
Coelacanth
Neopilina
LIFE ON THE SEA BOTTOM
Benthic Communities
Sources of Food for Benthic Organisms
Food Chains
Diversity of Benthic Organisms of the
Chapter Objectives
• Identify some of the unique adaptations to the pressure and cold of the deep sea.
• Explain how organisms can survive in total darkness.
• Describe the large species of the deep sea.
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Key Terms
disphotic zone
luciferin
bathyscaphe
Chapter Summary
1. In the deepest parts of the ocean, there is no sunlight, the temperatures are cold, and
2. Deep-sea animals metabolize more slowly, move more slowly, grow more slowly,
reproduce later in life, and generally live longer compared with their counterparts in
3. Food in the ocean’s depths is scarce. Some detritus that falls from above is consumed
4. Although most deep-sea species are small compared with similar shallow-water
5. Because the conditions of the deep have changed very little over the past 100 million
6. In 1977, oceanographers discovered thriving animal communities on the ocean floor.
These communities are located around deep-sea hydrothermal vents, which bring
Chapter Outline
I. Survival in the Deep Sea
A. Adaptations to pressure.
B. Adaptations to cold.
II. Life in the Dark
184 Life in the Ocean’s Depths
A. Color in deep-sea organisms.
1. Marine biology and the human connection—exploring the ocean’s depths.
B. Roles of bioluminescence.
C. Seeing in the dark.
D. Finding mates in the dark.
E. Finding food in the dark.
III. Giants of the Deep
A. Giant squids.
B. New species of deepwater squid.
IV. Relicts from the Deep
A. Spirula.
V. Life on the Sea Bottom
A. Benthic communities.
1. Sources of food for benthic organisms.
B. Vent communities.
1. Vent formation.
Suggestions for Presenting the Material
1. Assign students to locate online information on deep-sea bioluminescence. It is best
to review the luciferin-luciferase reaction ahead of time. Have students prepare a
group report comparing how bioluminescence is used by different taxa.
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Classroom Discussion Ideas
1. How can deep-sea research benefit society? Come up with a list of potential
discoveries with military, resource exploitation, or medical applications.
Videos, Animations, Websites
Videos
The Blue Planet: The Deep. (DVD, BBC, 2001)
Sea Monsters: Search for the Giant Squid. (DVD/VHS, National Geographic, 1998)
Follows researchers in search of the world’s largest invertebrate, using “crittercam”
Ocean Drifters. (VHS, National Geographic)
Follows a sea turtle hatchling as it travels through the Atlantic gyre; includes a sequence
on deep-sea planktonic and bioluminescent organisms.
Midwater Mysteries. (DVD, Discovery Channel, 2003)
Spotlights three undersea expeditions of Harbor Branch oceanographers as they explore
the mesopelagic zone.
Animation
Bathyscaph Trieste.
An interactive animation of the Trieste, the first manned vehicle to make it to the bottom
of the Mariana Trench.
Websites
Deep Sea Conservation Coalition.
Clearinghouse for deep-sea conservation issues, especially bottom trawling. Multimedia
Monterey Bay Aquarium Research Institute.
Excellent information on current deep-sea research in the Pacific Ocean.
NOAA Learning Objects: Lesson 6—Deepsea Benthos.
Presents an animated overview of the deep-sea habitat, discussing bioluminescence,
sensory capacities, and other adaptations of deep-sea benthos.
Deep Sea Challenge.
The website of the second manned expedition to the Mariana Trench in 2012.
Suggested Answers to End of Chapter Questions
Multiple Choice
1. b. move more slowly
2. c. light
Matching
1. d.
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Short Answer
1. What role does bioluminescence play in life in the deep?
Roles of bioluminescence include: camouflage, communicating with other
2. What adaptations have evolved in deepwater fish to help them find and capture prey?
Adaptations that deep-sea fish have evolved to find and capture prey generally fall
3. What role do vertical migrations play in bringing nutrients into deepwater?
Vertically migrating zooplankton ingest nutrients locked in the bodies of their
4. Why did early biologists think that animal life could not survive in the ocean’s
depths?
Early biologists thought the absence of primary producers in the ocean’s depths
5. Why are some deepwater animals bright red?
6. Why do some biologists believe that the sea’s depths may harbor organisms that have
changed very little from their early ancestors?
Some biologists believe deep-sea organisms are ancient relicts because the deep sea
7. What food sources are available for animals that live on the ocean floor?
Epibenthic deep-sea animals can be suspension feeders, deposit feeders, predators,
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8. Some deep-sea fish have larvae that rise to the surface waters, where they grow,
before settling to the depths. What is the advantage of this strategy?
One advantage of deep-sea anglerfish larvae developing in surface waters is that
Thinking Critically
1. How might you determine whether an animal in a hydrothermal vent community
derived its nutrition from symbionts or from feeding on other vent organisms?
You could isolate the animal in the laboratory and provide it with a source of H2S
2. The anglerfish spends the early part of its life in the upper regions of the ocean and its
adult life in the abyss. What kinds of anatomical changes would you expect to
observe as the animal matures?
When a juvenile anglerfish matures and migrates from the upper, photic regions of
3. Assuming deepwater fish could survive the physical environment of surface waters,
do you think they would be able to compete effectively with fish already adapted to
that environment? Explain.
Deepwater fish could not compete effectively with epipelagic fish. In the surface
4. Do you think deepwater fish have a swim bladder? Why or why not?
Deepwater fish lack a swim bladder. They are weak swimmers that mostly remain
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Suggested InfoTrac® Articles
“Close Encounters of the Deep-Sea Kind.” Dybas, C.L. Bioscience, (2004).