Review sheet – Chapter 15 (Plankton)
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Understand that marine life is divided into plankton (the drifting organisms), nekton (the
swimming organisms) and benthos (the bottom-dwelling organisms)
Know that plankton live in the pelagic zone
Know that phytoplankton are autotrophic and zooplankton are heterotrophic
Understand that a producer is an autotroph (capable of producing its own organic matter) while
consumers are heterotrophs, they must consume organic matter to survive
Understand that zooplankton are the most numerous primary consumers (first level of
consumers) in the ocean
Understand that zooplankton constitute (make up) the most important source of protein in the
oceans
Understand that zooplankton eat bacteria, phytoplankton, and other zooplankton
Know that holoplankton are always plankton; they spend their entire lives in the water column
Know that meroplankton are only plankton for part of their lives; most meroplankton are the
larvae, or young, of nektonic or benthic adult forms
Know that copepods are the most abundant of all zooplankton, and that they are holoplanktonic
Know that krill are holoplanktonic and dominate in cold, polar seas
Understand that Antarctic krill have a life span of 7 years and are a critically-important food
source for the Antarctic food web
Understand that pteropods are holoplanktonic marine snails, that may or may not have a shell
Understand that shell-less (naked) pteropods feed on shelled pteropods
Understand that ctenophores are holoplanktonic, but that jellyfish belonging to the phylum
Cnidaria are meroplanktonic (having a benthic polyp stage)
Understand that salps are holoplanktonic herbivores
Know that chaetognaths are predatory marine worms; and are holoplanktonic
Understand that the ocean sunfish, Mola mola, is considered to be a planktonic organism
because it can only weakly swim (or cannot swim at all) against most currents
Know that Reynold’s number is a measure of inertial forces (inertia) divided by viscous forces
(viscocity)
Understand that when viscous forces dominate (as it does for very small organisms), the
Reynold’s number is low
Understand that when inertial forces dominate (as it does for large organisms), the Reynold’s
number is high
Understand that many planktonic organisms have evolved ways to avoid sinking out of the
water column, and that these include increasing surface area/drag, gas-filled floats and
increased lipids
Understand that you can’t really parachute from a jellyfish…
Understand that many planktonic organisms have evolved ways to avoid being eaten, and that
these include translucence, spines, and swimming behavior (and red coloration for deep sea
species)
Understand that zooplankton take part in the greatest migration on Earth, migrating towards
the surface at night, and away from the surface during daytime