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 Production

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

Respiration: – 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?

Respiration

Gross and Net Production• The production of biomass and it’s use as a source

of energy by autotrophs includes three steps:

1. Gross Production: An organism produces organic matter within it’s body

2. It uses some of this new organic matter as a fuel in respiration

3. 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 Ecosystems1. 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 autotrophs.

Measures of Primary Production

in Aquatic Ecosystems1. 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 form

•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 energy.

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

http://www.mlms.logan.k12.ut.us/~mlowe/EnergyPyramid.gif

•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

1. An initial kind of vegetation specially adapted to the unstable conditions

2. Small plants and other early-successional species grow and seeds spread rapidly.

3. Larger plants and other late successional species enter and begin to dominate the site.

4. 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– Specialists– __________ 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.