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Environmental Sys. & Soc. Study Guide
Pages 46-68
(by Kyleigh Estes)
Energy Stores and Flows
Interpreting diagrams:
 Boxes=stores
 Arrows=flows
o Sometimes the width of the arrow can represent the amount of energy (J)
in that flow.
Energy Loss:
 Mammals lose more energy to the environment because of the high levels of
respiration needed to maintain body temperature and higher activity
 Herbivores (plant eaters) take in large amounts of indigestible substances like
cellulose and lose the energy from these substances in feces.
Transfer and Transformation of Materials within an Ecosystem
 Unlike energy, nutrients are recycled in ecosystems This recycling is necessary to
the Earth in order to maintain the availability of nutrients.
Carbon Cycle:
 Stores of Carbon:
o Biological molecules (e.g. carbohydrates, fats, proteins)
o Biomass
o Fossil Fuels (e.g. coal, gas, peat, oil)
o Limestone
Figure 1: Carbon Cycle Diagram

Processes that return Carbon to the atmosphere
o Weathering of limestone
o Acid rain
o Combustion of fossil fuels
Nitrogen Cycle:
 Nitrogen is an essential building block of amino acids and nucleic acids and is the
most abundant gas in the atmosphere.
 The Nitrogen Cycle is driven by four types of bacteria:
o Nitrogen-fixing bacteria
o Decomposers
o Nitrifying bacteria
o Denitrifying bacteria
Figure 2: Nitrogen Cycle Diagram



Lightning fixes atmospheric nitrogen into ammonia.
Ammonia is also found in excretory products from decomposers, along with
ammonium compounds.
The ammonia is oxidized by the nitrifying bacteria and is turned into nitrates. The
denitrifying bacteria then return it to the atmosphere.
Water (Hydrologic) Cycle:
 Refers to the entire path of water through the atmosphere, lithosphere, and
biosphere.
Figure 3: Hydrologic Cycle Diagram
Productivity
Primary vs. Secondary:
Primary productivity—The gain by producers (autotrophs) in energy or biomass per unit
area per unit time
 Conversion of solar energy
 Depends on amount of sunlight, availability of growth factors, and ability of
producers to use energy in order to synthesize organic compounds.
 At its highest where growth conditions are optimal
Secondary productivity—The biomass gained by heterotrophic organisms, through
feeding and absorption, measured in units if mass or energy per unit area per unit time.
 Depends on amount of food present and the efficiency of consumers turning it
into new biomass.
Gross vs. Net:
Gross productivity (GP)—The total gain in energy or biomass per unit area per unit time
Net productivity (NP)—The gain in energy or biomass per unit area per unit time
remaining after allowing for respiratory losses
Population Changes
Limiting Factors and Carrying Capacity:
Carrying capacity—The maximum number of organisms that an area or ecosystem can
sustainably support over a long period of time
Limiting factors:
 Temperature
 Water and nutrient availability
S and J Curves:
 S-Curve:
o Graphical approach to depicting population change that occurs in 3 stages.
o 3 Stages
 Exponential growth—Population grows at an increasingly rapid
rate
 Transitional—Population growth slows considerably, but continues
to grow due to limiting factors.
 Plateau—Population growth stabilizes at a lower level
 J-Curve:
o Graph that shows only the exponential growth of a population
Survivorship Curves:
 Show changes in the survivorship over the lifespan of species
 “r” and “K” Strategists
“r” Strategists
“K” Strategists
Initial colonizers
Dominant species
Large number of a few species
Diverse range of species
Highly adaptable
Generalists
Rapid growth and development
Slow development
Early reproduction
Delayed reproduction
Short life
Longer living
Small size
Larger size
Very productive
Less productive
 Factors that influence survivorship rates:
o Competition for resources
o Adverse environmental conditions
o Predator-prey relationships
Density Dependency:
 Density-dependent factors—A limiting factor related to population density that
acts as a negative feedback mechanism and can include:
o The size of the breeding population
o The size of the territory

Density-independent factor—A limiting factor related to population density that
are generally abiotic and affect the population and can include:
o Weather (drought, fire, hurricane)
o Long-term climate change
Internal vs. External Factors:
 Internal factors—Density-dependent fertility or size of breeding territory
 External factors—Predation or disease
Human Involvement:
Population Growth Caused by Human Population Decline/Extinction Caused by
Involvement
Human Involvement
Increase available resources (e.g. farming) Change the physical environment and
cause habitat disruption (e.g. draining of
bodies of water)
Reduce competition (e.g. pesticides)
Change the biological environment by
introducing a new species
Reduce predators (e.g. over-hunting large Overkill (e.g. big-game hunting)
carnivores)
Introduce animals to new areas (e.g. game Cause secondary extinctions (e.g. loss of
releases)
food species)
Succession:
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
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Different types of succession
o On bare rock= lithosere
o In a freshwater habitat= hydrosere
o In a dry habitat=xerosere
Primary succession—succession occurring on a previously uncolonized substrate
Secondary succession—succession occurring in a place where a previous
community has been destroyed (faster than primary succession because of the
presence of soil)