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Chapter 14

Chapter 14 - Intro to Oceanography Chapter 14 I How Are...

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Intro to Oceanography : Chapter 14 I. How Are Marine Organisms Able to Stay above the Ocean Floor? a. Use of Gas Containers i. Rigid Gas Containers 1. Cephalopods have rigid gas containers in their bodies to keep themselves afloat ii. Swim Bladders 1. A change in depth either expands or contracts the swim bladder, so fish must remove or add gas to maintain a constant volume b. Ability to Float i. Microscopic forms usually have a hard shell or test. Many larger forms have soft, gelatinous bodies with little if any hard tissue, which reduces their density and allows them to stay afloat ii. Examples of Microscopic Floating Zooplankton 1. Radiolarians – single-celled, microscopic organisms that build their hard shells (tests) out of silica 2. Foraminifers – microcopic to (barely) macroscopic single- celled animals. Most are benthic. Hard tests of calcium carbonate 3. Copepods – microscopic shrimplike animals of the subphylum Crustacea, which includes shrimps, crabs, and lobsters; most numerically dominant types of multi-celled organisms on the planet iii. Examples of Macroscopic Floating Zooplankton 1. Krill – in the subphylum Crustacea and resemble minishrimp or large copepods 2. Cnidarians – formerly known as coelenterates have soft body more than 95% water and tentacles armed with stinging cells called nematocysts 3. Hydrozoan – have gas chambers called pneumatophores which serve as floats and sails that allow the wind to push them across the ocean surface 4. Scyphozoan (or jellyfish) – have a bell-shaped body with a fringe of tentacles and a mouth at the end of the clapper-like extension hanging beneath the bell-shaped float c. Ability to Swim i. Examples of Swimming Organisms 1. Squid 2. Locomotion in fish occurs when a wave of lateral body curvature passes from the front of the fish to the back. This is achieved by the alternate contraction and relaxation of muscle segments, called myomeres, along the sides of the body. The backward pressure of the fish’s body and fins produced by the movement of this wave provides the forward thrust.
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ii. Fin Designs in Fish 1. Two sets of fins – pelvic fins and pectoral fins – to turn, brake, and balance 2. Vertical fins, both dorsal and anal, serve primarily as stabilizers 3. Caudal fin – tail fin that is most important in propelling high- speed fish 4. 5 Basic Fin Shapes a. Rounded fins – flexible and useful in accelerating and maneuvering at slow speeds b. Truncate fins and forked fins – on faster fish; are somewhat flexible for better propulsion but are also used for maneuvering c. Lunate fins – fsat-cruising fish such as tuna; fins are
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Chapter 14 - Intro to Oceanography Chapter 14 I How Are...

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