Adapting to Life in the Ocean
• Adaptation- process
whereby a population
becomes better suited to its
habitat; takes place over
many generations
• Adapting to salinity
– Osmotic stress- sudden
change in solute
concentration around a cell,
causing movement of water
across its membrane. Under
conditions of high salinity,
water is drawn out of the
cells through osmosis
– Osmotic pressure- the
pressure that must be applied
to a solution to prevent the
inward flow of water across a
semipermeable membrane
Osmoregulation- active
regulation of osmotic
pressure of an organism’s
fluids to maintain water
content; it keeps organism’s
fluids from becoming too
dilute or too concentrated
– Osmoconformer- match their
body osmolarity (salinity) to
their environment
– Osmoregulator- regulate their
body osmolarity by actively
controlling salt
concentrations despite salt
concentration of the
environment
• Osmoregulator
– Stenohaline- restricted to either salt or fresh
water and cannot survive in water with a different
salt concentration than they are adapted to
– Euryhaline- show a tremendous ability to
effectively osmoregulate across a broad range of
salinities
• Adapting to temperature
– Organisms lose heat more quickly in water than in
air
– Adaptations
• Ectotherm/ poikilotherm- internal body temperature
varies along with the ambient environmental
temperature; dependent on environmental heat
sources; relatively low metabolic rates (most fishes and
reptiles)
• Adaptations
– Endotherm- internal body temp. varies but is
elevated above ambient environmental temps as a
result of metabolic heat production (some fishes)
– Homeotherm- internal body temp. remains
relatively constant despite the ambient
environmental temp. (birds and mammals)
• Adapting to viscosity
– Viscosity – describes a fluid’s internal resistance to
flow; water is “thin”, having a lower viscosity, while
honey is “thick”, having a higher viscosity
– Drag – refers to forces that oppose the relative motion
of an object through a fluid
– Hydrodynamic adaptations
• Fusiform- body shape characterized by being tapered at both
the head and the tail
• Fish secrete mucous from glands under their skin; reduces
drag by 60%
• Sharks have denticles on their skin that cause the water to
form a thin film that reduces drag in much the same way as
the slimy mucous
• Adapting to pressure
– Hydrostatic pressurepress. At a given depth in a
static liquid is a result of
the weight of the liquid
acting on a unit area at
that depth plus any
pressure acting on the
surface liquid
– Pressure increases 1
atmosphere (or bar) for
every 10 meter or 33 ft of
depth in ocean water
– Adaptations
• Light skeletons and water
muscles
• Fluid filled body cavities
rather than gas- filled
spaces
• Piezophile- organism that
thrives at high pressures
(deep sea bacteria or
acrhaea)
• Buoyancy- upward force,
caused by fluid pressure
that keeps things afloat
– Archimedes’ principle- any
object, wholly or partially
immersed in a fluid, is
buoyed up by a force equal
to the weight of the fluid
displaced by the object
– Adaptations
• Small size reduces sinking
(plankton)
• Using fins as hydrofoils
(sharks)
• Using low –density organic
compounds (oil) or body
fluids (plankton, sharks)
• Gas- filled bladders (bony
fishes)