January 29th notes

January 29th

Marine Zonation

Benthic Organisms  

  • Live on or burrowed in the bottom or sediments
  • Some are attached and immobile = sessile (corals, plants tend to be attached to the bottom of the ocean)
  • Some crawl around, on or in sediment – mobile
  • Sea stars can be both sessile and mobile

Pelagic Organisms

  • Live up in the water column
  • Further subdivided according to size and swimming ability (Plankton and Nekton(squid, fish and anything swimming in the water column)


  • Swim weakly, float around at mercy of currents
  • Phytoplankton: Algae, tiny plants, photosynthetic bacteria
  • Zooplankton: Tiny animals and protozoans – microcrustaceans, rotifers, larvae, etc.
  • Ex ( Fish larvae)
  • Nekton
    • Animals that swim well enough to oppose currents
    • Mainly fishes , marine animals

Benthic Zone

Is the ecological region at the lowest level of a body of water in the ocean, lake, or stream, including the sediment surface and some sub-surface layers.

Intertidal zone

  • Shallowest part of the continental shelf
  • Tides cause exposure to air at times
  • Smallest fraction of the continental shelf

Subtidal zone

  • Beyond the intertidal, always submerged
  • Where coral reefs are found

Deep ocean floor

Photic zone

  • Where light can penetrate
  • Usually 50 to 100 meters

Aphotic zone

Absence of sunlight, no photosynthesis

Physical properties of water

  • Humidity
    • Prevents drying out or desiccation
    • Exposed respiratory surfaces (gills)  
    • External fertilization and development


  • The study of the interactions between organisms and their environment ( abiotic and biotic)  
  • THese interactions determine the distribution and abundance of organisms.
  • Abiotic (non living factors)  
    • Humidity, sand , etc
  • Biotic (living factors)
    • Producers,
      • Green plants, Algae (Phytoplankton)
    • All are autotrophic _ they feed themselves through photosynthesis
    • Use sunlight energy to convert inorganic compounds into large organic compounds
    • Photosynthesis / Some chemosynthetic bacteria  
    • Photosynthesis equation
    • 6Co2 + 6 H20 —> Glucose and 6O2
    • Consumers,
    • Animals, Zooplankton, Other Heterotrophs
    • Cellular respiration
    • Break down the organic fuel molecules in food to harvest energy
    • Glucose + Oxygen —-> Carbon dioxide + Water + energy (ATP)
    • Decomposers

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