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Ying Chao Xie
December 7, 2018
Section 1: Marine Environment
· Plankton are organisms that drift with ocean currents; an example would be phytoplankton. Nekton are animals capable of moving independently of the ocean currents; an example would be a gray reef shark. Benthos are organisms living on or in the ocean bottom; an example would be a coral crab.
· The photic zone is the upper portion of the ocean in which light levels are sufficient to support photosynthesis. In the open ocean, this layer is 100-200 meters deep. If autotrophic planktonic organisms sink below 200 meters, then they die. Marine diatoms are much smaller than freshwater diatoms; their increased surface area to volume ratio keeps them afloat. Additionally, marine diatoms have ornate spines that increase surface area. Many freshwater diatoms live in habitats where light penetrates to the bottom so sinking is not problematic. Freshwater diatoms lack the ornate spines frequently observed in marine diatoms because light penetrates to the bottom of the pond, stream, or puddle where they live.
· Body tissues in a saltwater fish contain less salt than the water in which it lives. The saltier environment draws water from its body tissues, resulting in constant water loss through its skin and gills. To compensate and prevent dehydration, saltwater fish drinks large amounts of saltwater, produces small amounts of concentrated (salty) urine, and secretes salt through its gills. In contrast, body tissues in a freshwater fish contain more salt than the water it lives in. As such, its body continually draws in water through its skin and gills. Due to this constant water ‘intake’, freshwater fish drinks very little water and produces copious amounts of diluted urine to avoid excessive water in its body tissues.
· The ocean bottom contain habitat that marine species have adapted too, such as rocky, sandy, muddy environments at the...