Chapter 15

Chapter 15 - Ch.15: Animals of the Pelagic Environment...

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Ch.15: Animals of the Pelagic Environment
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Cephalopod adaptations for maintaining buoyancy: Nautilus – external shell with air chambers inside; Sepia & Spirula – internal shells with air chambers. These air chambers provide buoyancy.
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Nautiloids control their buoyancy by pumping water into their chambers, which displaces the air causing their buoyancy to increase.
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Slow swimming fish have the ability to inflate or deflate an internal air sac called a swim bladder to maintain neutral buoyancy. The source/sink of the air is the fish’s blood, where it exists in a dissolved form. As the fish sinks, overlying water pressure increases which caused swim bladder to shrink, causing th fish to become more dense. This reduction in swim bladder volume must be offset by increasing the bladders size through the addition of gas from the bloodstream.
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Microscopic Zooplankton Floating zooplankton constitute the second greatest source of biomass in the oceans, next to floating phytoplankton. These are images of radiolarians, that secrete a siliceous test (shell) for increased buoyancy and protection from predation.
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Foraminifera – another important microzooplankton that forms a calcareous test.
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Copepods – microscopic crustacea (same subphylum as shrimp, crabs, lobsters, etc.) Probably represent the majority of the ocean’s zooplankton biomass. Figure on left shows female copepod carrying egg sacs; figure on right shows copulating copepods.
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Upper figure shows a warm water copepod with elaborate ornamentation. Why do warm water copepods generally have more elaborate ornamentation than cold water ones? Lower figure shows a copepod with feathered appendages that It uses to trap food, cling to larger particles or other zooplankton in the water column
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Macroscopic Zooplankton Krill are a highly abundant macrozooplankton. They are crustacea, similar to shrimp, that form an important link in the marine food chains particularly in the Antarctic Ocean.
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Cnidaria are another important group of macrozooplankton. They include the hydrozoa (e.g., Portugese man-o’-war and By the wind sailor) and the scyphozoa (e.g., jellyfish). These organisms are colonial (composed of multiple individuals), > 95% water, and usually contain nematocysts (stinging cells) along their tentacles in the medusa form. Jellyfish move through muscular contraction.
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This note was uploaded on 03/22/2009 for the course GEOL 103 taught by Professor Dr.ries during the Fall '08 term at UNC.

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Chapter 15 - Ch.15: Animals of the Pelagic Environment...

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