Summation
A phenomenon of neural integration in which the membrane potential of the postsynaptic
cell in a chemical synapse is determined by the total activity of all excitatory and inhibitory
presynaptic impulses acting on it at any one time.
Superior
Inserted or situated abovr the perianth. Used of an ovary.
Suppressor T cell (TS)
A type of T cell that causes B cells as well as other cells to ignore antigens.
Suppressor genes
A gene that is able to reverse the effect of a specific kind of mutation in other genes.
Surface tension
A measure of how difficult it is to stretch or break the surface of a liquid. Water has a high
surface tension because of the hydrogen bonding of surface molecules.
Survivorship curve
A plot of the number of members of a cohort that are still alive at each age; one way to
represent age-specific mortality.
Suspension-feeder
An aquatic animal, such as a clam or a baleen whale, that sifts small food particles from the
water.
Sustainable agriculture
Long-term productive farming methods that are environmentally safe.
Sustainable development
The long-term prosperity of human societies and the ecosystems that support them.
Swim bladder
An adaptation, derived from a lung, that enables bony fishes to adjust their density and
thereby control their buoyancy.
Symbiont
The smaller participant in a symbiotic relationship, living in or on the host.
Symbiosis
An ecological relationship between organisms of two different species that live together in
direct contact.
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