survivorship curves: Type I applies to species having a
high survival rate of the young, where most of the indi-
viduals of the population survive to maturity and die in
old age, such as humans. Type II species have a rela-
tively constant death rate throughout their life span,
such as fish and large birds. Type III curves are found
in species that have many young, most of which die
very early in their life, such as plants. Most type III off-
spring die before they reach reproductive age.
suspension Particles mixed with, but undissolved, in
a fluid or solid.
suspension feeder(suspensivores) An organism that
obtains food by capturing organic matter suspended in
the water. Those that use a filter to capture food are
called filter feeders. A mucous-bag suspension feeder
uses a sheet or bag of mucous to trap particles, while a
tentacle-tube-foot suspension feeder traps particles on
distinct tentacles or tube feet.
sustainable Aprocess that can continue indefinitely
without overusing resources and causing damage to the
environment.
sustainable agriculture Agricultural techniques and
systems that, while economically viable to meet the
need to provide safe and nutritious foods, utilize
nonenvironmentally destructive methods such as the
use of organic fertilizers, biological control of pests
instead of pesticides, and minimized use of nonrenew-
able fuels.
sustainable development Development and eco-
nomic growth that meets the requirements of the pre-
sent generation without compromising the ability of
future generations to meet their needs. Seeks a balance
between development and conservation of natural
resources.
Sutherland, Earl W., Jr. (1915–1974) American
Pharmacologist Earl Sutherland was born on Novem-
ber 19, 1915, in Burlingame, Kansas. He received a
B.S. from Washburn College in 1937 and an M.D.
from Washington University School of Medicine in St.
Louis in 1942.
Sutherland joined the faculty of Washington Uni-
versity, and in 1953 he became director of the depart-
ment of medicine at Western Reserve University in
Cleveland, Ohio. Here he discovered cyclic AMP
(adenosine monophosphate) in 1956.
In 1963 he became professor of physiology at Van-
derbilt University in Nashville, Tennessee. He was
awarded the 1971 Nobel Prize in physiology or
medicine for isolation of cyclic adenosine monophos-
phate (cyclic AMP) and for demonstrating its involve-
ment in numerous animal metabolic processes. From
1973 until his death he was a member of the faculty of
the University of Miami Medical School.
He died on March 9, 1974, in Miami, Florida. The
Earl Sutherland Prize award is presented annually by
the chancellor of Vanderbilt University to a Vanderbilt
faculty member who has made a nationally recognized
impact in a particular discipline.swim bladder(air bladder) An organ—a gas-filled
sac—that lies in the upper body cavity of many bony
fishes; functions as a ballast tank by creating buoyancy;
also used in respiration and as a sound organ.symbiont One of the members of a symbiotic
relationship.symbiosis A mutually beneficial relationship
between two or more different kinds of organisms in
direct contact with each other.
See alsoMUTUALISM.sympathetic division One of two divisions of the
autonomic nervous system—the sympathetic and
parasympathetic—that regulates involuntary func-
tions. The sympathetic division prepares the body for
survival response while under stress and increases
energy use; autonomic motor neurons release the neu-
rotransmitter norepinephrine, which accelerates
heartbeats, constricts or dilates blood vessels, dilates318 suspension