I
n the 5th century BCE, the Greek
historian Herodotus described
watching crocodiles open their
jaws for plovers to pick food from
their teeth. He may have been the
first to write about an ecological
process—in this case a mutualistic
relationship between reptiles and
birds. Aristotle and Theophrastus
observed many more interactions
between animals and their
environment in the 4th century BCE.
Over the next two millennia,
countless other observations of the
natural world were made, but a deep
understanding of how organisms
interacted with each other and the
world around them was hampered
by the inability to observe very
small things, those that were active
at night, or those living underwater.
Additionally, few people with an
interest in nature experienced muchbeyond their own local area. As
technology improved and people
began to travel the world, scientists
such as Robert Hooke, Antonie van
Leeuwenhoek, Carl Linnaeus,
Alexander von Humboldt, Alfred
Russel Wallace, Charles Darwin,
and Johannes Warming became
increasingly aware of ecological
processes and laid the foundations
of the science of ecology, even if
they didn’t use that word.Mathematical models
It had long been understood that
one of the most basic ecological
processes is the struggle for
survival: for herbivores to find food,
predators to find prey, and prey to
avoid being eaten. Predators do
everything they can to hunt and
eat prey, and the latter do all they
can to avoid being eaten. In 1910,Alfred Lotka introduced one of the
first mathematical models ever
applied to ecology. Now known
as the Lotka-Volterra model, its
predator–prey equations help
predict the population fluctuations
of these two groups.
In the early years of the 20th
century, Joseph Grinnell conducted
extensive research into animals’
habitat needs in the western United
States. He observed that species
had different “niches” within a
habitat—and that if two species
have approximately the same food
requirements, one will “crowd out”
the other. Darwin had observed this
on his travels aboard HMS Beagle,
but Grinnell’s axiom developed the
idea further, as did subsequent
research. In 1934, Georgy Gause
demonstrated what he called the
competitive exclusion principle inINTRODUCTION
1917
Joseph Grinnell publishes
his research on the California
Thrasher, establishing the
basis for the theory of
ecological niches.1957
Robert MacArthur’s
research on North American
warblers shows how different
species can avoid directly
competing with each other
in order to coexist.1965
Dan Janzen observes the
interdependence of acacia
trees and the ants that reside
on them, and concludes that
the species evolved in a
mutualistic manner.1925 – 26
The Lotka-Volterra model uses
a mathematical equation to
describe the interactions between
predator and prey.1961
Joseph Connell reveals that
different types of barnacle
thrive in different tidal
zones, although they could,
in theory, live in any of them.1969
Robert Paine
coins the term “keystone
species” to describe species
that play a crucial role in
ecosystem functions.42
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