Download Concepts in contemporary ecological theory

Concepts in contemporary ecological theoryi
Ecology is the study of relationship between a species and its environment.
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Environment consists of all those objects and forces external to the organism with which it interacts or
by which it is affected.
Most organisms exist in units known as populations, groups of individuals of the same species who
occupy the same given area and interbreed with one another.
The specific area where a population lives is its habitat.
The niche of a population in an environment is its place or how it makes a living (its “profession”).
Habitat is a concrete idea whereas niche is more abstract concept; since it includes how the
population interacts with both natural resources and other populations.
Adaptation is the process by which organisms or populations make biological or behavioral
adjustments that facilitate their survival and reproductive success in their environment.
Ecosystem – cycle of matter, information and energy that includes all organic things and links them to
inorganic.
Exchanges of energy, matter, and information can go on through a number of trophic levels, or levels
of feeding relationships, i.e., producers, herbivores, and consumers.
Sequence of exchange is also known as the food chain.
Every environment is limited in ability to support life.
 Limiting factors (food, water, temperature, rainfall, presence of disease causing organisms, etc.) help
determine the carrying capacity of an environment—the point at or below which a population tends
to stabilize or, alternatively, the limit to which a population can grow and still be supported by the
environment.
 Carrying capacity is really the maximum number of individuals of a population that a given ecosystem
can support without experiencing irreversible damage.
 Carrying capacity determined not just by the total amount of food available (i.e., calories) but also by
quality of food in form of proteins, vitamins, minerals.
 For human populations, carrying capacity can vary with technology.
Two important properties of ecosystems: stability and resilience.
 Resilience is a measure of the degree of change a system can undergo while still maintaining its basic
elements or relationships.
 Stability is a measure of the speed with which a system returns to equilibrium after absorbing
disturbances.
 Ecosystems may be highly resilient, yet have low stability, taking longer to return to equilibrium. But
despite the long period necessary to return to stability they continue to persist as systems because
their parts do not change.
 On the other hand, ecosystems may be highly stable – they return to equilibrium quickly – but have
low resilience because they are likely to collapse.
How/why are humans different from every other species?
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Human interaction with the environment differs from all other animal species in two ways:
1. While the niche of most animal species is relatively narrow ... humans occupy an exceptionally
broad ecological niche and can be found in an extremely wide range of habitats.
2. Once humans enter an ecosystem they tend to become the dominant species and affect the
survival and adaptiveness of other species.
The ability to modify environment (through technology) means that humans can and do create
artificial environments (farms & cities) that must be sustained with enormous inputs of energy, matter
and information.
With globalization these inputs can be drawn not just from local ecosystem but often from very far
away.
Tremendous ability to modify environment means that human dominated ecosystems are often
considerably less resilient than other ecosystems.
They can be maintained only by constant expenditure of human energy and ingenuity.
Evolutionary ecology – study of living organisms within context of their total environment, with the aim of
discovering how their evolved characteristics and strategies for survival contribute to their success in that
environment.
 Combines synchronic (present-oriented) research from ecology with diachronic (concerned with
change over time) perspective of evolution.
 With regard to humans the theoretical orientation of evolutionary ecology emphasizes the adaptive
significance of culture and behavior – from food procurement systems to kinship systems to political
and religious systems.
 Dual inheritance of humans -- cultural transmission and change works simultaneously with a parallel
process of natural selection.
 In the process of adapting, humans are active decision makers and innovations lead to change.
 Flexibility is the key.
 "The organism with the best chance of reproductive success is not necessarily the one
most perfectly adjusted to its environment at any particular point, but rather the one
that maintains its ability to respond to the environment in a flexible variety of ways"
(Bates)
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Taken largely from Daniel Bates’ book Human Adaptive Strategies.
Trophic levels in an ecosystem
Illustration of carrying capacity