GLOSSARY G11
r-strategists Seer-selected species.
rule of 70 Doubling time (in years)
70/(percentage growth rate). See doubling time,
exponential growth.
salinity Amount of various salts dissolved in a
given volume of water.
salinization Accumulation of salts in soil that
can eventually make the soil unable to support
plant growth.
scavenger Organism that feeds on dead or-
ganisms that were killed by other organisms or
died naturally. Examples include vultures, fl ies,
and crows. Compare detritivore.
science Attempts to discover order in nature
and use that knowledge to make predictions
about what is likely to happen in nature. See
reliable science, scientifi c data, scientifi c hypothesis, sci-
entifi c law, scientifi c methods, scientifi c model, scientifi c
theory, tentative science, unreliable science.
scientifi c data Facts obtained by making ob-
servations and measurements. Compare scientifi c
hypothesis, scientifi c law, scientifi c methods, scientifi c
model, scientifi c theory.
scientifi c hypothesis An educated guess that
attempts to explain a scientifi c law or certain sci-
entifi c observations. Compare scientifi c data, scientifi c
law, scientifi c methods, scientifi c model, scientifi c theory.
scientifi c law Description of what scientists
fi nd happening in nature repeatedly in the same
way, without known exception. See fi rst law of
thermodynamics, law of conservation of matter, second
law of thermodynamics. Compare scientifi c data,
scientifi c hypothesis, scientifi c methods, scientifi c model,
scientifi c theory.
scientifi c methods The ways scientists gather
data and formulate and test scientifi c hypothe-
ses, models, theories, and laws. See scientifi c data,
scientifi c hypothesis, scientifi c law, scientifi c model,
scientifi c theory.
scientifi c model A simulation of complex
processes and systems. Many are mathematical
models that are run and tested using computers.
scientifi c theory A well-tested and widely
accepted scientifi c hypothesis. Compare scientifi c
data, scientifi c hypothesis, scientifi c law, scientifi c meth-
ods, scientifi c model.
secondary consumer Organism that feeds
only on primary consumers. Compare detritivore,
omnivore, primary consumer.
secondary succession Ecological succession
in an area in which natural vegetation has been
removed or destroyed but the soil or bottom
sediment has not been destroyed. See ecological
succession. Compare primary succession.
second-growth forest Stands of trees result-
ing from secondary ecological succession. Com-
pareold-growth forest, tree farm.
second law of energy Seesecond law of ther-
modynamics.
second law of thermodynamics In any
conversion of heat energy to useful work, some
of the initial energy input is always degraded
to lower-quality, more dispersed, less useful
energy—usually low-temperature heat that
fl ows into the environment; you cannot break
even in terms of energy quality. See fi rst law of
thermodynamics.
selective cutting Cutting of intermediate-
aged, mature, or diseased trees in an uneven-
aged forest stand, either singly or in small
groups. This encourages the growth of younger
trees and maintains an uneven-aged stand.
Compareclear-cutting, strip cutting.
sexual reproduction Reproduction in organ-
isms that produce offspring by combining sex
cells or gametes (such as ovum and sperm) from
both parents. It produces offspring that have
combinations of traits from their parents. Com-
pareasexual reproduction.
social capital Result of getting people with
different views and values to talk and listen to
one another, fi nd common ground based on
understanding and trust, and work together to
solve environmental and other problems.soil Complex mixture of inorganic minerals
(clay, silt, pebbles, and sand), decaying organic
matter, water, air, and living organisms.
solar capital Solar energy that warms the
planet and supports photosynthesis, the process
that plants use to provide food for themselves
and for us and other animals. This direct input
of solar energy also produces indirect forms of
renewable solar energy such as wind and fl ow-
ing water. Compare natural capital.
solar energy Direct radiant energy from the
sun and a number of indirect forms of energy
produced by the direct input of such radiant
energy. Principal indirect forms of solar energy
include wind, falling and fl owing water (hydro-
power), and biomass (solar energy converted
into chemical energy stored in the chemical
bonds of organic compounds in trees and other
plants)—none of which would exist without
direct solar energy.
sound science Seereliable science.
specialist species Species with a narrow eco-
logical niche. They may be able to live in only
one type of habitat, tolerate only a narrow range
of climatic and other environmental conditions,
or use only one type or a few types of food.
Comparegeneralist species.
speciation Formation of two species from one
species because of divergent natural selection in
response to changes in environmental condi-
tions; usually takes thousands of years. Compare
extinction.
species Group of similar organisms, and for
sexually reproducing organisms, they are a set
of individuals that can mate and produce fertile
offspring. Every organism is a member of a
certain species.
species diversity Number of different species
(species richness) combined with the relative
abundance of individuals within each of those
species (species evenness) in a given area. See
biodiversity, species evenness, species richness. Com-
pareecological diversity, genetic diversity.species equilibrium model Seetheory of
island biogeography.
species evenness Relative abundance of indi-
viduals within each of the species in a commu-
nity. See species diversity. Compare species richness.
species richness Number of different species
contained in a community. See species diversity.
Comparespecies evenness.
S-shaped curve Leveling off of an expo-
nential, J-shaped curve when a rapidly grow-
ing population reaches or exceeds the carrying
capacity of its environment and ceases to grow.
statistics Mathematical tools used to collect,
organize, and interpret numerical data.
stewardship worldview Worldview holding
that we can manage the earth for our benefi t
but that we have an ethical responsibility to be
caring and responsible managers, or stewards,
of the earth. It calls for encouraging environ-
mentally benefi cial forms of economic growth
and discouraging environmentally harmful
forms. Compare deep ecology worldview, environ-
mental wisdom worldview, planetary management
worldview.
stratosphere Second layer of the atmosphere,
extending about 17–48 kilometers (11–30 miles)
above the earth’s surface. It contains small
amounts of gaseous ozone (O 3 ), which fi lters
out about 95% of the incoming harmful ultra-
violet radiation emitted by the sun. Compare
troposphere.
stream Flowing body of surface water.
Examples are creeks and rivers.
subatomic particles Extremely small par-
ticles—electrons, protons, and neutrons—that
make up the internal structure of atoms.
succession Seeecological succession, primary suc-
cession, secondary succession.
succulent plants Plants, such as desert cacti,
that survive in dry climates by having no leaves,
thus reducing the loss of scarce water. They
store water and use sunlight to produce the
food they need in the thick, fl eshy tissue of their
green stems and branches. Compare deciduous
plants, evergreen plants.
sulfur cycle Cyclic movement of sulfur in
various chemical forms from the environment to
organisms and then back to the environment.
sulfur dioxide (SO 2 ) Colorless gas with an
irritating odor. About one-third of the SO 2 in
the atmosphere comes from natural sources as
part of the sulfur cycle. The other two-thirds
come from human sources, mostly combustion
of sulfur-containing coal in electric power and
industrial plants and from oil refi ning and smelt-
ing of sulfi de ores.
surface fi re Forest fi re that burns only under-
growth and leaf litter on the forest fl oor. Com-
parecrown fi re, ground fi re. See controlled burning.
surface water Precipitation that does not in-
fi ltrate the ground or return to the atmosphere
by evaporation or transpiration. See runoff.
Comparegroundwater.