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I
n biology, there are several
kinds of interaction between
organisms. One species in an
ecosystem may lose out to another
when competing for the same
resources. A prey species may be
eaten by a predator. There are also
symbiotic relationships, in which
one species benefits but not at the
expense of the other, or where one
organism does not benefit but still
survives. In the relationship known
as “mutualism,” both organisms
benefit from the relationship.A tree and its ants
In the mid-1960s, Daniel Janzen,
a young American ecologist,
became fascinated by the amazingIN CONTEXT
KEY FIGURE
Dan Janzen (1939 –)BEFORE
1862 Charles Darwin proposes
that an African orchid with
a long nectar receptacle must
be pollinated by a moth with
an equally long proboscis.1873 Belgian zoologist Pierre-
Joseph van Beneden first
uses the term “mutualism”
in a biological context.1964 The term “coevolution”
is first used by American
biologists Paul Ehrlich and
Peter Raven to describe
the mutualistic relations
between butterflies and
their food plants.AFTER
2014 Researchers discover
an unusual yet beneficial
three-way mutualism involving
sloths, algae, and moths.MORE NECTAR
MEANS MORE ANTS
AND MORE ANTS
MEAN MORE NECTAR
MUTUALISMS
US_056-059_Mutualisms.indd 56 12/11/18 6:24 PM