NARE 221: NATURAL RESOURCES ECOLOGY
The Scope of Ecology
Skills to Develop
Define ecology and the four levels of ecological research
Describe examples of the ways in which ecology requires the integration of different
scientific disciplines
Distinguish between abiotic and biotic components of the environment
Recognize the relationship between abiotic and biotic components of the environment
Ecology is the study of the interactions of living organisms with their environment. One core
goal of ecology is to understand the distribution and abundance of living things in the physical
environment. Attainment of this goal requires the integration of scientific disciplines inside and
outside of biology, such as biochemistry, physiology, evolution, biodiversity, molecular biology,
geology, and climatology. Some ecological research also applies aspects of chemistry and
physics, and it frequently uses mathematical models.
NB: Climate change can alter where organisms live, which can sometimes directly affect human
health.
Levels of Ecological Study
When a discipline such as biology is studied, it is often helpful to subdivide it into smaller,
related areas. For instance, cell biologists interested in cell signaling need to understand the
chemistry of the signal molecules (which are usually proteins) as well as the result of cell
signaling. Ecologists interested in the factors that influence the survival of an endangered species
might use mathematical models to predict how current conservation efforts affect endangered
organisms. To produce a sound set of management options, a conservation biologist needs to
collect accurate data, including current population size, factors affecting reproduction (like
physiology and behavior), habitat requirements (such as plants and soils), and potential human
influences on the endangered population and its habitat (which might be derived through studies
in sociology and urban ecology). Within the discipline of ecology, researchers work at four
specific levels, sometimes discretely and sometimes with overlap: organism, population,
community, and ecosystem.
See figures below ..
Figure1: Ecologists study within several biological levels of organization. (Source:
organisms: modification of work by "Crystl"/Flickr; Source: ecosystems: modification of
work by Tom Carlisle, US Fish and Wildlife Service Headquarters; Source: biosphere: NASA)
Organismal Ecology
Researchers studying ecology at the organismal level are interested in the adaptations that enable
individuals to live in specific habitats. These adaptations can be morphological, physiological,
and behavioral. For instance, the Karner blue butterfly (Lycaeides melissa samuelis)
(Figure below) is considered a specialist because the females preferentially oviposit (that is, lay
eggs) on wild lupine. This preferential adaptation means that the Karner blue butterfly is highly
dependent on the presence of wild lupine plants for its continued survival.
Figure2: The Karner blue butterfly (Lycaeides melissa samuelis) is a rare butterfly that lives
only in open areas with few trees or shrubs, such as pine barrens and oak savannas. It can only
lay its eggs on lupine plants. (Source: modification of work by J & K Hollingsworth, USFWS)
After hatching, the larval caterpillars emerge and spend four to six weeks feeding solely on wild
lupine (Figure3 below). The caterpillars pupate (undergo metamorphosis) and emerge as
butterflies after about four weeks. The adult butterflies feed on the nectar of flowers of wild
lupine and other plant species. A researcher interested in studying Karner blue butterflies at the
organismal level might, in addition to asking questions about egg laying, ask questions about the
butterflies preferred temperature (a physiological question) or the behavior of the caterpillars
when they are at different larval stages (a behavioral question).
Figure3: The wild lupine (Lupinus perennis) is the host plant for the Karner blue butterfly.
Population Ecology
A population is a group of interbreeding organisms that are members of the same species living
in the same area at the same time. (Organisms that are all members of the same species are
called conspecifics.) A population is identified, in part, by where it lives, and its area of
population may have natural or artificial boundaries: natural boundaries might be rivers,
mountains, or deserts, while examples of artificial boundaries include mowed grass, man-made
structures, or roads. The study of population ecology focuses on the number of individuals in an
area and how and why population size changes over time. Population ecologists are particularly
interested in counting the Karner blue butterfly, for example, because it is a unique species on its
own right. However, the distribution and density of this species is highly influenced by the
distribution and abundance of wild lupine. Researchers might ask questions about the factors
leading to the decline of wild lupine and how these affect Karner blue butterflies. For example,
ecologists know that wild lupine thrives in open areas where trees and shrubs are largely absent.
In natural settings, intermittent wildfires regularly remove trees and shrubs, helping to maintain
the open areas that wild lupine requires. Mathematical models can be used to understand how
wildfire suppression by humans has led to the decline of this important plant for the Karner blue
butterfly.
Community Ecology
A biological community consists of the different species within an area, typically a three-
dimensional space, and the interactions within and among these species. Community ecologists
are interested in the processes driving these interactions and their consequences. Questions about
conspecific interactions often focus on competition among members of the same species for a
limited resource. Ecologists also study interactions among various species; members of different
species are called heterospecifics. Examples of heterospecific interactions include predation,
parasitism, herbivory, competition, and pollination. These interactions can have regulating
effects on population sizes and can impact ecological and evolutionary processes affecting
diversity.
For example, Karner blue butterfly larvae form mutualistic relationships with ants. Mutualism is
a form of a long-term relationship that has coevolved between two species and from which each
species benefits. For mutualism to exist between individual organisms, each species must receive
some benefit from the other as a consequence of the relationship. Researchers have shown that
there is an increase in the probability of survival when Karner blue butterfly larvae (caterpillars)
are tended by ants. This might be because the larvae spend less time in each life stage when
tended by ants, which provides an advantage for the larvae. Meanwhile, the Karner blue butterfly
larvae secrete a carbohydrate-rich substance that is an important energy source for the ants. Both
the Karner blue larvae and the ants benefit from their interaction.
Ecosystem Ecology
Ecosystem ecology is an extension of organismal, population, and community ecology. The
ecosystem is composed of all the biotic components (living things) in an area along with
the abiotic components (non-living things) of that area. Some of the abiotic components include
air, water, and soil. Ecosystem biologists ask questions about how nutrients and energy are
stored and how they move among organisms and the surrounding atmosphere, soil, and water.
The Karner blue butterflies and the wild lupine live in an oak-pine barren habitat. This habitat is
characterized by natural disturbance and nutrient-poor soils that are low in nitrogen. The
availability of nutrients is an important factor in the distribution of the plants that live in this
habitat. Researchers interested in ecosystem ecology could ask questions about the importance of
limited resources and the movement of resources, such as nutrients, though the biotic and abiotic
portions of the ecosystem.
Whos an Ecologist?
A career in ecology contributes to many facets of human society. Understanding ecological
issues can help society meet the basic human needs of food, shelter, and health care. Ecologists
can conduct their research in the laboratory and outside in natural environments (Figure4). These
natural environments can be as close to home as the stream running through your campus or as
far away as the hydrothermal vents at the bottom of the Pacific Ocean or side of a mountain.
Ecologists manage natural resources such as white-tailed deer populations (Odocoileus
virginianus) for hunting or aspen (Populus spp.) timber stands for paper production. Ecologists
also work as educators who teach children and adults at various institutions including
universities, high schools, museums, and nature centers. Ecologists may also work in advisory
positions assisting local, state, and national policymakers to develop laws that are ecologically
sound, or they may develop those policies and legislation themselves. To become an ecologist
requires an undergraduate degree, usually in a natural science. The undergraduate degree is often
followed by specialized training or an advanced degree, depending on the area of ecology
selected. Ecologists should also have a broad background in the physical sciences, as well as a
sound foundation in mathematics and statistics.
Figure4: This landscape ecologist is releasing a black-footed ferret into its native habitat as part
of a study. (Source: USFWS Mountain Prairie Region, NPS)
Summary
Ecology is the study of the interactions of living things with their environment. Ecologists ask
questions across four levels of biological organizationorganismal, population, community, and
ecosystem. At the organismal level, ecologists study individual organisms and how they interact
with their environments. At the population and community levels, ecologists explore,
respectively, how a population of organisms changes over time and the ways in which that
population interacts with other species in the community. Ecologists studying an ecosystem
examine the living species (the biotic components) of the ecosystem as well as the nonliving
portions (the abiotic components), such as air, water, and soil, of the environment.
Glossary
abiotic
biotic
conspecifics
ecology
heterospecifics
