Transcript Subphylum Vertebrata – Early Vertebrates and

Deep-sea Ecosystems
 The Mesopelagic Zone (~200-1000 m): from photosynthetic-
compensation depth to limit of down-welling sunlight
(below = aphotic zone)
 Photosynthetic-compensation Depth: depth where sunlight
becomes too low for phytoplankton to maintain positive
metabolism (above = euphotic zone)
 Deep-scattering Layer: layer of zooplankton and small fishes that
rises at night; shows a scattering effect on SONAR traces
 Major Selection Pressures in the Deep Sea
 Light (low or none): large and specialized eyes common,
bioluminescence common (light emitted without heat, luciferin
and luciferase; multiple functions)
 Temperature (cold) and Density (high): slow metabolisms; little
muscle necessary to maintain position
 Pressure (high): fishes often lack swim bladder
 Food Availability (low): fishes with large mouths and teeth
Figure 14-31
Deep-sea Ecosystems
 Deep-sea Communities: benthic communities more diverse
than once believed (bias regarding sampling via nets and
bottom grabs vs. observations via submersibles & ROVs)
 Hydrothermal-vent Communities: diverse communities in aphotic
zone (pogonophoran worms, crustaceans, bivalves, fishes)
supported by chemosynthetic bacteria (use hydrogen sulfide;
symbiotic relationships support animals); discovered in 1970s
 Whale Falls: most dead whales sink to seafloor; animal communities
similar to those at vents; researchers found 5,098 animals (178
species) on one square yard of bone
 Gigantism: giant squids, sleeper sharks, giant isopod; a result of
slow metabolisms, long life spans?
 Living Fossils: coelacanth, Nautilus, Neopilina (snail); related to
stable conditions (few extinctions?)
Figures 11-12 and 14-34
Figures 14-33 and 11-15
Figure 14-32
Plate Tectonics
 Continental Drift and Pangaea (Wegener, 1915); lacked explanation
of how continents could move
 Theory of Plate Tectonics (Hess, 1960s) based on observations via
SONAR and magnetometers (World War II technologies)

Major plates of Earth’s crust float on semi-molten upper mantle





Divergence (spreading centers at mid-ocean ridges): new oceanic crust
produced (basalt); Mid-Atlantic Ridge best studied
Convergence (subduction zones): old crust pushed down at fault; associated
with deep-sea trenches, high seismic and volcanic activities (Ring of
Fire around Pacific basin)
Sliding Faults: lateral movement of plates (ex. San Andreas Fault)
Hot Spots: localized volcanic activity (away from faults); create island chains
as plates move (ex. Hawaiian islands)
Evidence: areas of seismic and volcanic activity; shapes of continents
and correspondence of fossils, strata, and extant species;
magnetic stripes and age gradients of seafloor
Figures 11-4 and 11-5
Figure 11-6
Figures 11-1 and 11-2
Figure 11-10
Figures 11-18 and 11-19
Figures 11-21 and 11-22
Figures 11-8 and 11-9
Figure 11-11
Figure 11-13
Figure 11-14
Figure 11-17
Figure 11-24