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Biological Productivity
and Energy Flow
Biological Production
• Biomass - the total amount of organic matter on
Earth or in any ecosystem. Measured in terms of
mass per unit of space. Examples: kg/hectare or MT
(metric tons)/hectare or g/m2(square meter).
• Biological Production- the capture of usable
energy from the environment to produce organic
compounds in which that energy in stored. Two
types. Measured by the amount of food produced
per area per time period. Examples: gram/m2/day
or kg/ hectare/day.
Two Kinds of Biological
1. Primary Production
Photosynthetic organisms make their own
organic matter from a source of energy and
an inorganic compound and convert it to
organic compounds
Carried out by autotrophs and chemoautothrophs
Examples: photosynthesis & chemosynthesis
2. Secondary Production
Cannot make their own organic compounds
and therefore must feed on other living things
Carried out by heterotrophs
– the use of biomass to release energy that can
be used to do work
– In other words, the use of energy from organic
matter by most heterotrophic and autotrophic
organisms is accomplished through respiration.
– An organic compound such as sugar is
combined with oxygen to produce carbon
dioxide and water.
– Compare to photosynthesis. Do you remember
the formula for photosynthesis and the formula
for respiration? How do these two things relate?
Gross and Net Production
The production of biomass and it’s use as a source of
energy by autotrophs includes three steps:
Gross Production: An organism produces organic
matter within it’s body
It uses some of this new organic matter as a fuel in
It stores some of the newly produced organic matter
for future use
The amount left after use during respiration is Net Production
Net Production (NPP) = Gross Production (GPP)- Respiration (Ra)
Controlling Primary Production
• Primary production is controlled by different factors in terrestrial
versus aquatic ecosystems.
• Water: Influences terrestrial (aquatic systems are not water
limited) ecosystems are largely influenced by water – greater
precipitation/soil moisture increases primary production.
• Temperature: terrestrial and aquatic; higher temperatures
increase primary production (think about how temperature
increases chemical reaction rates).
• Light: production in aquatic systems is limited by light because
light is quickly attenuated at depth; terrestrial systems are not as
limited as aquatic systems by light, but since light and
temperature are related, light does play an indirect role in
terrestrial systems via temperature.
• Nutrients: terrestrial and aquatic; increased nutrient availability
results in greater primary production; productivity in terrestrial
systems tends to be limited by nitrogen, whereas productivity
in aquatic systems tends to be limited by phosphorus.
Measures of Primary Production
in Terrestrial Ecosystems
1. Primary production is measured differently in terrestrial versus
aquatic ecosystems.
2. CO2 Method: this method measures the net consumption of
CO2 in the light to determine NPP and the production of CO2
in the dark to determine respiration (R)
3. Harvest Method: This method is based on measuring the
standing crop biomass at two different times. The difference
between each time is the NPP.
4. Satellite: Satellite sensors quantify the spectral pattern of
reflected light off of photosynthetic organisms, which
provides an index of NPP. In terrestrial ecosystems
measurement of visible and near-infrared wavelengths
reflected off vegetation (Normalized Difference Vegetation
Index; NDVI) is used to estimate the productivity of terrestrial
Measures of Primary Production
in Aquatic Ecosystems
1. Satellite: Satellite sensors are also used in aquatic ecosystems
to quantify the spectral pattern of reflected light off of
photosynthetic organisms, which provides an index of NPP.
For example, measurement of the spectral signature of
chlorophyll a in water bodies is used to estimate the
productivity of aquatic primary producers (autotrophs).
2. Light/dark bottle (oxygen) method: This method measures the
net production of O2 in the light to determine NPP and the
consumption of O2 in the dark to determine respiration (R) in
aquatic ecosystems.
Energy Flow
• Ecosystem Energy Flow
– The movement of energy through an
ecosystem from the external environment
through a series of organisms and back to the
external environment
The Laws of Thermodynamics
• 1st Law of Thermodynamics
- (the law of conservation of energy)
-Energy is neither created nor destroyed. It is
merely changed from one form to another
• 2nd Law of Thermodynamics
- Energy always changes from a more useful,
higher quality from to a less useful, lower quality
•Thermodynamic System
- Formed by an energy source, ecosystem and
energy sink, where the ecosystem is said to be an
intermediate system between the energy source
and the energy sink (degraded heat energy)
Energy Efficiency and
Transfer Efficiency
Energy Efficiency
-the ratio of output to input, or the amount of useful
work obtained by some amount of available
Trophic-level efficiency
- Also known as food chain efficiency.
- It is an ecological measure of energy efficiency
- the ratio of production of one trophic level to the
production of the next lower trophic level
Energy Pyramid of Trophic- Level Efficiency
•10 percent of the energy at one level of a food web is transferred to the
next, higher, level.
•The other 90 percent of the energy is used for the organism's life processes
or is lost as heat to the environment.
Question: How many kcals would transfer to the 4th order consumer if there
was one?
QUESTION: Why are there so few organisms at the top of the pyramid?
See page 173
Energy Pyramids Continued
• The organisms at higher feeding levels of an energy
pyramid do not necessarily require less energy to
live than organisms at lower levels. Since so much
energy is lost at each level, the amount of energy in
the producer level limits the number of consumers
the ecosystem can support. As a result, there
usually are few organisms at the highest level in a
food web and increasingly more organisms as you
move down the energy pyramid to successively
lower feeding levels.
Ecological Restoration
The Balance of Nature
– An environmental myth that states that
the natural environment, when not
influenced by human activity, will reach a
constant status, unchanging over time.
– Biomes have reached some consistency
and this is known as a climax community,
but this is different from climax state,
which according to the Balance of
Nature would continue indefinitely.
– In truth ecosystems do change – think
about the biomes that require fire.
What needs to be restored?
As we have been studying, biomes and the ecosystems
within have been undergoing degradation and are in
great need of restoration. Examples from your text:
1. Wetlands, Rivers and Streams
(Ex: Kissimmee River, Everglades National Park)
2. Prairie Restoration
(Ex: Allwine Prairie)
When Nature Restores Itself:
The Process of Ecological Succession
Ecological Succession:
The process of the development of an
ecological community or ecosystem.
Two Types:
1. Primary Succession: The initial
establishment and development of an
ecosystem. No previous life exists.
Pioneer species are the first.
2. Secondary Succession: The
reestablishment of an ecosystem where
there are remnants of a previous
biological community
Which is which and why?
Patterns in Succession
An initial kind of vegetation specially adapted to
the unstable conditions
Small plants and other early-successional species
grow and seeds spread rapidly.
Larger plants and other late successional species
enter and begin to dominate the site.
A mature forest develops.
Examples of Succession:
Dune Succession, Bog Succession, Old-Field Succession
Bog Succession
Reproductive Strategies
• R-strategists
– Many offspring, low parental care, reproduce rapidly
– Read reproductive age early, low survival rate, short lifespan,
short generation time
– Seen in unstable environments – often pioneer species
– ________ successional species, opportunists, type _______
– Generalists, Also prone to population crashes when competitive
species move in.
– Example: dandelions
• K-strategists
Few offspring, reproduce late
Mature slowly
High survival rate
High parental care
Seen in stable environments
__________ successional species
More prone to extinction
Example: gorilla
Survivorship curve
Survivorship Curve
• Type I survivorship curves are for species that have
a high survival rate of the young, live out most of
their expected life span and die in old age.
– Humans are a good example of a species with a Type I
survivorship curve.
• Type II survivorship curves are for species that have
a relatively constant death rate throughout their life
span. Death could be due to hunting or diseases.
– Examples of species exhibiting a Type II survivorship curve
are coral, squirrels, honey bees and many reptiles.
• Type III survivorship curves are found in species that
have many young, most of which die very early in
their life.
– Plants, oysters and sea urchins are examples of species that
have Type III survivorship curves.
Species Change in Succession
Earlier and later species in succession may
interact in three ways:
If they do not interact, the result is termed
chronic patchiness – where the species
that enters first remains until the next time
the ecosystem is disturbed.
1. Facilitation
• During succession, one species
prepares the way for the next (and
may even be necessary for the
occurrence of the next)
• Example: The pine tree provides the
shade to allow the oak to grow.
2. Interference
• During succession, one species
prevents the entrance of a later
species into an ecosystem.
• Ex) Some grasses produce dense and
thick mats so the seeds of trees cannot
reach the soil to germinate
Life History Difference
• The difference in the life histories of the
species allow some time to arrive first
and grow quickly, while others arrive
late and grow more slowly.
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