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Ecology Notes.docx

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Biology 2483A

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The Web of Life : Ecology 10/15/2012
Definition of Ecology
The scientific interactions between organisms and their environment
E.g. sidewalk and corn field
Organisms are important part of one another’s environment
The scientific study of interactions that determine the distribution (geographic location) and abundance of
Why organisms happen to be one area when they are not in another?
Why some organism are more successful in some area in terms of population ?
Other meanings in public usage
Differs from environmental activism and environmental science (solution to environmental problems)
Environmental science is an interdisciplinary field that incorporates concepts from the natural sciences (including
ecology) and the social sciences
Focused on how people affect the environment and how we can address the environmental problems
General Misconceptions
Balance of nature – natural systems are stable and tend to return to original preferred state after disturbance
Not always the case
Communities and ecosystems are dynamic (always changing)
We would end up with different end point after disturbance
Some predictable patterns but we cannot always predict the exact outcome ; random factor
Each species has a distinct role to play in maintaining that balance
Not necessarily
Many species are similar
A lot of redundancy in ecosystem and community; even if we loose one species, nothing would happen to the whole
Some species are a lot more important than others in terms of how the system functions
The different species in an area often respond in different ways to changing conditions.
7 Ecological Maxims (guiding principles)
1. Organism interact and are interconnected (interaction)
Connections could be relatively weak because the communities are complex
Organism interact with on another and with their physical environment. As a result, events in
nature are connected, and what affects one organism or place can effect others as well.
2. Everything goes somewhere
any production, energy, and release of nutrients all end up in somewhere
there is no “away” into which waste materials disappear.
3. No population can increase in size forever
What is the limit imposed on the population ?
There are limits to the growth and resources use of every population, including humans.
4. Finite energy and resources result in tradeoffs
Any decision that organisms might make has another consequence.
E.g. Super organisms that outcompete others must have some way that is overcompensated and
weak in another area.
An organism’s energy and resources are finite, and increasing inputs into one function (such as
reproduction) results in a trade-off in which there is a loss for other functions (such as growth)
5. Organisms evolve
Adaptation and Natural selection
oAdaptation: a characteristic that improves survival or reproduction
The process that makes organisms better suited to their habitat
oNatural selection: individuals with certain adaptations tend to survive and reproduce at
a higher rate than other individuals.
oIf the adaptation is heritable, the frequency of the characteristic may increase in a
population over time.
E.g. antibiotic resistance
oBacteria that is resistance to one will not be resistance to the one anymore
oNatural selection can cause the frequency of antibiotic resistance in bacteria to
increase over time
Organisms evolve or change over time – it is a mistake to view them as static. Evolution is an
ongoing process because organisms continually face new challenges from changes in both the
living and nonliving components of their environment.
6. Communities and ecosystems change over time
They change over time; not static
We are often biased by our own time scale on which we operate.
Ecosystems change over time. When we look at the world as we know it, it is easy to forget how
past events may have affected our present, and how our present actions may affect the future.
7. Spatial scale matters
How we organize the ecological system
E.g. physiology ecologist often study at the level of organism and advance to population,
community, ecosystem and finally biosphere
oHow we define each of these level
oHow this hierarchy system constructed
oUsually people are specialized in one specific area
Organism < population < community < ecosystem < biosphere
oPopulation: group of individuals of same species that are living and interacting in a
particular area.
oCommunity: association of population of different species in the same area.
Spatial definition could be complicated because of migrations, so their boundaries are hard to
oMetapopulation : consists of a group of spatially separated populations of the same
species which interact at some level.
Address the connection between different populations
Abiotic and biotic environmental conditions can change dramatically from one place to another,
some across very short distances. This variation matters because organisms are simultaneously
influenced by processes acting at multiple spatial scales, from local to regional to global.
Ecological studies often include both the biotic (living components), and abiotic (physical components) of
natural systems.

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