General Principles of Ecology
Ecology is the study of how organisms interact with one another and with their environment. Environment can be split into two components; the
living portion, termed the biotic component (e.g., organisms), and the nonliving portion, termed the abiotic component (e.g., air, soil, water, etc.).
Ecologists organize the biosphere into several levels. A population is a group of individuals of the same species occupying a common geographic
area. A community is formed when two or more populations reside in the same geographic location. An ecosystem is comprised of a community and
its surrounding abiotic factors. A biome is a collection of ecosystems with similar climates and communities.
Energy Flow
Food webs describe the flow of energy within an ecosystem by linking together several food chains. Each food chain begins with an organism that
uses energy from light or chemical reactions to produce organic compounds from inorganic compounds through photosynthesis or chemosynthesis,
called an autotroph (also referred to as a producer). Any organism that can't produce its own organic compounds and must consume other organisms
to obtain them is called a heterotroph (also referred to as a consumer).
Picture
Heterotrophs can be further organized based on what they consume:
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Herbivore-a heterotroph that only consumes plants
Carnivore-a heterotroph that only consumes animals
Omnivore-a heterotroph that consumes both plants and
animals
Detritivore-a heterotroph that consumes detritus (dead and
decaying organic matter)
Decomposer-a heterotroph that breaks down dead and
decaying organic matter using biochemical reactions
Note that as opposed to detritivores, decomposers break down dead and
decaying organic matter using biochemical reactions without ingesting
it.
Each "step" in a food chain is called a trophic level. For example,
autotrophs comprise the first trophic level of a certain food chain, the
heterotrophs that consume those autotrophs make up the second trophic
level, and so on. Within each food chain, only about 10% of the amount
of energy that is initially available to one trophic level is available to the
organisms in the next trophic level.
Biogeochemical Cycles
A biogeochemical cycle is a description of the pathways a chemical
substance takes to recycle itself. Some of the most important
biogeochemical cycles are depicted in the table below.
Community Interactions
Competition
As described above, competition is an
interaction that is detrimental to both
species. Competition can be described as
intraspecific (among individuals of the
same species) or interspecific (between
different species).
Competition occurs when two or more
species occupy the same niche. A niche is
the conditions in which an organism lives
and the way the organism uses those
conditions (such as how they utilize a
resource), and is sometimes described as
the functional role of an organism in a
community. According to the competitive exclusion principle, no two
species that occupy the same niche can coexist indefinitely; eventually
one species will always reign dominant and lead to the eventual
extinction of the other. This can be avoided by the organisms undergoing
a shift towards different niches.
Aquatic Environment: About 40% of all humans live within 100 km of
a coastline, so humans have a large impact on aquatic environments.
Dead Zones: A "dead zone" occurs when the aquatic environment is very low on dissolved oxygen. Many aquatic organisms depend on oxygen to
survive, so with low concentrations of oxygen, organisms will die out or leave for other areas with higher oxygen levels. This creates a dead zone
with very little aquatic life.
The state of having low oxygen levels is also known as hypoxia. The state of almost no dissolved oxygen is known as anoxia.
. Acid rain is the effect that occurs when greenhouse gases, primarily sulfur dioxide and nitrous oxides, are dissolved into water droplets in the air.
This leads to a high concentration of hydrogen ions in the rain, which in turn results in an acidic solution (ph below 7).
Climate Change
Climate Change is defined as the change in weather patterns over an extended period of time. Factors that can determine and affect climate are called
forcing mechanisms. Forcing mechanisms can be further classified as either internal or external. In Green Generation, the greatest emphasis is on
external forcing mechanisms, primarily human influences.
Bioremediation is the use of biological organisms to clean up an environment. Generally the term refers to the use of microbes to decontaminate a
polluted area, but the term can apply to plants and fungi as well.
Renewable Energy
Renewable energy comes from resources that can be renewed relatively quickly, such as wind or vegetation. The use of renewable energy can
prevent ecological damage if a resource is only utilized under a sustainable yield.
Resources can be divided into three classifications based on how promptly they are renewed:
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Perpetual-resource is continuously and instantaneously renewed on a human timescale (e.g., solar energy, wind, etc.)
Renewable-although not instantaneously, resource is renewed on a human timescale (e.g., vegetation, etc.)
Nonrenewable-resource is in a fixed supply on a human timescale; take a very long time to be renewed (e.g., coal, oil, etc.)
Deserts: characterized by low moisture levels and infrequent, unpredictable precipitation
Grasslands/Savannas: rich biological communities of grasses, seasonal flowering plants, seasonal cycles for temperature and precipitation.
Tundra: characterized by a short growing season, cold, harsh winters, and the potential for frost at any time; less than 10" rainfall per year
Conifer/Boreal Forest/Taiga: cold temps; 20-40" of rain per year; conifer trees can survive harsh winters or extended droughts
Deciduous Forest: lush summer plant growth; requires adaptations for the frozen season 30-100" rain per year; four seasons
Tropical Rain Forest: one of the most complex and biologically rich biomes; uniform temperatures (about 80 degrees); 90-180" rain per year)
AQUATIC ECOSYSTEMS
Estuaries: bays of brackish water (mix of salt and fresh water) from where river enters ocean; nutrient-rich; high species diversity and productivity
Wetlands: land surface is covered with standing water at least part of the year; vegetation is adapted; swamps, wetlands, bogs; low productivity
TERMS TO KNOW FOR MARINE ECOSYSTEMS (ALSO BE ABLE TO POINT THEM OUT ON AN ILLUSTRATION)
Intertidal: between high and low tide which is subjected to periods of wet and dry
Aphotic: deep water areas where no sun penetrates
Neritic: area from low tide to the edge of the continental shelf. Relatively stable in salinity, oxygen and temperature.
Benthic: bottom-dwelling organisms**
Littoral Zone: shore of lake bottom where light penetrates
Euphotic Zone: area in ocean that light penetrates.