Page 79 - Environment: The Science Behind the Stories

species—these processes and more have combined to threaten Biosphere
Earth’s biodiversity (pp. 301–308). The sum total of
When we look around us, it may not appear as though a living things on
human version of an asteroid impact is taking place, but we can- Earth and the
not judge such things on the timescale of a human lifetime. On areas they
inhabit
the geologic timescale, extinction over 100 years or even 10,000
years appears instantaneous. In contrast, speciation is a slow
enough process that it will take life millions of years to recover—
by which time our own species will most likely not be around.

Levels of Ecological Ecosystem

Organization A functional
system consisting
of a community,
Extinction, speciation, and other evolutionary mechanisms its nonliving
and patterns play key roles in ecology. Ecology is the scien- environment,
and the
tific study of the distribution and abundance of organisms, the interactions
interactions among organisms, and the relationships between between them
organisms and their environments. It is often said that ecology
provides the stage on which the play of evolution unfolds. The
two are intertwined in many ways.

Community
We study ecology at several levels A set of
Life exists in a hierarchy of levels, from atoms, molecules, and populations of
different species
cells (pp. 41–47) up through the biosphere, which is the cumu- living together in
lative total of living things on Earth and the areas they inhabit. a particular area
Ecologists are scientists who study relationships at the higher
levels of this hierarchy (Figure 3.11), namely at the levels of the
organism, population, community, ecosystem, and biosphere.
At the level of the organism, the science of ecology describes
relationships between an organism and its physical environ-
ment. Organismal ecology helps us understand, for example,
what aspects of a Hawaiian honeycreeper’s environment are Population
important to it, and why. In contrast, population ecology exam- A group of
ines the dynamics of population change and the factors that individuals of a
affect the distribution and abundance of members of a popula- species that live
in a particular
tion. It helps us understand why populations of some species area
(such as endangered honeycreepers) decline while populations
of others (such as ourselves) increase.
In ecology, a community consists of an assemblage of
populations of interacting species that live in the same area.
A population of ‘akiapo¯la¯ ‘au, a population of koa trees, a
population of wood-boring grubs, and a population of ferns,
together with all the other interacting plant, animal, fungal, Organism
and microbial populations in the Hakalau Forest, would be An individual
considered a community. Community ecology focuses on pat- living thing
terns of species diversity and on interactions among species,
ranging from one-to-one interactions to complex interrela-
tionships involving the entire community.
Ecosystems encompass communities and the abiotic
(nonliving) material and forces with which community mem-
bers interact. Hakalau’s cloud-forest ecosystem consists of its
community plus the air, water, soil, nutrients, and energy used
by the community’s organisms. Ecosystem ecology reveals pat-
terns, such as the flow of energy and nutrients, by studying Figure 3.11 Ecologists study questions on the levels of
living and nonliving components of systems in conjunction. the organism, population, community, ecosystem, and
Today’s warming climate (Chapter 18) is having ecosystem- biosphere.
78 level consequences as it exerts impacts on the organisms of

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