Principles of Ecology

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Principles of Ecology

• its all connected

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Outline

• Definition
• Areas of Study
• Ecosystem Structure
• Ecosystem Function
• Key Principles
• Limiting factors
• Holocoenotic principle

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Ecology
The scientific study of the relationships between
organisms and their environments.
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E. Odums Layer Cake
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Levels of Organization Spectrum
Ecological Focus
From Odum, 1971
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Population ecology -- the structure and dynamics
of populations. Physiology -- individual
characteristics and individual processes, a basis
for prediction of processes at the population
level. Community ecology -- the structure and
dynamics of animal and plant communities.
Population ecology provides modeling tools for
predicting community structure and dynamics.
Systems ecology -- studies interaction of human
population with environment, major concepts
optimization of ecosystem exploitation and
sustainable ecosystem management. Landscape
ecology -- regional large-scale ecosystems with
the aid of computer-based geographic information
systems.
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Ecosystem Structure
Abiotic Biotic
Inorganic substances Organic substances Climate P
roducers Macro-consumers Micro-consumers
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Climate
Seasonal variation Spatial variation
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Seasonal variation
driven by Earths annual rotation around the
sun equinoxes and solstices
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Spatial Variation Global Scale
rainfall and temperature
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Spatial Variation Global Scale
wind patterns
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Spatial Variation Regional Scale
Elevation Proximity to water bodies Relationship
between winds and topographic features
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Biotic Elements
Producers - plants Macro-consumers -
animals Micro-consumers - bacteria fungi
Individuals Populations a group of individuals
of any one kind at the same time and in the same
place Communities all populations occupying the
same area at the same time
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Population A group of individuals of any one
kind of organism at the same place at the same
time.
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Measuring Population
Numbers measured as Density Size measured as
Biomass Cover - Cover
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Temporal Population Dispersal
Growing Stagnant Declining
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Patterns of Population Growth
Exponential Growth
Cyclic (without control) with
Control Growth
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Population Regulation
Extrinsic
Intrinsic
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Population Regulation
Density Dependent Genetic Physiological Hormona
l Genetic Behavioral Dominance Territorialit
y Density Independent
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Population Dynamics
Extrinsic factors/Intrinsic factors Density
dependent /Density independent factors
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Species
A group of actually or potentially interbreeding
populations that are reproductively isolated from
all other kinds of organisms.
Differentiation caused by
Recombination
Mutation
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Speciation
One Species
Two Varieties Same species
Two Species
Barrier or Distance
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Community
All populations occupying the same area at the
same time. Vertical Structure
Horizontal Structure
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Distinct Communities
Ecotone
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Whittakers Vegetation Classification
superimposed On the range of terrestrial climates
From Ricklefs, 1979
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Ecosystem Function
Food chains Energy circuits Natural
cycles Succession Control
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Food Chains/Webs
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Energy Circuits
Energy and Matter in Ecosystems or Landscape
Elements 1st Law of Thermodynamics Materials
are recycled. matter cannot be created
or destroyed Energy flows one way. You cant
even break even entropy increases energy
available for work decreases sun chemical
energy chemical energy mechanical energy
photosynthesis food
work
waste heat
waste heat
waste heat
waste heat
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Net Primary Production

• Gross Primary Production
• Rate at which an ecosystem can solar energy into
  chemical energy as biomass
• Net Primary Production
• Rate at which producers use photosynthesis to
  store energy minus what they use for respiration
• NPP GPP - R

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Energy Pyramid
From Ricklefs, 1979
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NPP is variable

• Most productive ecosystem types
• swamps and marshes (wetlands)
• tropical rain forests
• estuaries
• Least productive ecosystem types
• desert
• open ocean

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Natural Cycles - Physical
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Natural Cycles - Chemical

• Carbon
• Phosphorus
• Nitrogen
• Oxygen

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Succession
Directional species replacement
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Cyclic Succession
Pioneering stage
Climax Community
From Odum, 1971
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Sub-climax Communities
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Control Feedback Loops Negative Feedback One
component stimulates a second, which then
inhibits the first, e.g., Predator Prey cycles,
parasitism. Positive Feedback One component
stimulates a second, which then stimulates the
first, e.g., Symbiotic relationship bull horn
acacia and ants
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Predator Prey Relationship
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Principle of Limiting Factors
there is always a limit
Too much or too little of any abiotic factor can
limit or prevent growth of a population.
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• Climate as a limiting factor
• Chemical compounds as a limiting factor

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Solar radiation
Holocoenotic principle
man
water
animals
other plants
fire
topography geographic position
soil
From Billings, 1952
gravity