Greenhouse effect The way in
which gases in Earth’s atmosphere
trap heat. The buildup of these
gases leads to global warming.Greenhouse gas Gases such as
carbon dioxide and methane that
absorb energy reflected by Earth’s
surface, stopping it from escaping
into space.Green Movement A political
ideology that encourages a greater
focus on the importance of the
environment, and asks people to
take action to prevent damage
to Earth’s natural habitats.Groundwater Water found below
Earth’s surface, such as in spaces
in the soil, sand, or rock.Habitat The area in which
an organism naturally lives.Herbivore An organism that eats
only plants.Homeostasis The regulation
of conditions within an organism,
such as temperature, water, and
carbon dioxide, to maintain a
stable internal state.Hypothesis An idea or assumption,
used as the starting point for
a theory, which is then tested
through scientific experimentation.Inheritance The passing on of
genetic qualities and behavioral
predispositions to offspring,
through both genetic information
and parental nurture.Invasive species A nonnative
species that has been introduced
to an ecosystem and spreads
rapidly, damaging the ecological
balance of the area.Irrigation The controlled
application of water to areas of
land, usually through the creation
of channels, to help crops grow.Keystone species A species
that plays a centrally important
role in an ecosystem, often
disproportionate to its biomass,
and whose removal would alter
or endanger the entire ecosystem.Kin selection An evolutionary
strategy whereby individuals
pursue the best tactic for their
relatives’ survival, even at the
expense of their own safety, well-
being, or reproduction.Mass extinction The widespread
and rapid dying out of an abnormally
large number—at least half—of
all species; this sharp change in
biodiversity usually marks a shift
to a new geological era in our
planet’s history.Metabolism The chemical
processes that occur within the
cells of an organism to keep it alive,
such as the processes that enable
the digestion of food.Metacommunity A set of
independent communities that
interact and are connected by
the movement of some species
between those communities.Metapopulation A collection
of smaller populations of a given
species that are linked by the
movement of some individuals.Microorganism An organism,
invisible to the human eye,
that can only be seen with a
microscope, such as a bacterium,
virus, or fungus; also known as
a microbe.Migration A large-scale movement
of a species from one environment
to another; often occurs seasonally.Monoculture Using land for the
cultivation or growth of only one
type of plant or animal. This often
has damaging effects on the land,
as it can decrease its mineral value.Morphology The study of the
external structure of organisms.Mutation A change of
structure within an organism’s
DNA, which may result in a
genetic transformation giving
it uncharacteristic traits. One
example of a mutation is
albinism, a lack of pigmentation.Mutualism A situation in which
two or more organisms depend
on each other for survival.Mycorrhizae Types of fungi
that grow among the roots of
plants and exist in a symbiotic
relationship with these plants.Natural selection The process
by which characteristics that
increase an organism’s chances
of reproducing are preferentially
passed on.Niche The specific space and
role that a species occupies within
an ecosystem.Omnivore An organism that feeds
on both animals and plants.Organism General term for
any living thing, from single-cell
bacteria to complex, multicellular
life forms such as plants and animals.Ornithology A branch of biology
that concerns the study of birds.342 GLOSSARY
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