Chapter 9 Biological Productivity and Energy Flow

Biological Production The ultimate limit on production of organic matter is energy flow. Biomass - the total amount of organic matter on Earth or in any ecosystem. - amount per surface area Biological Production -the capture of usable energy from the environment to produce organic compounds in which that energy in stored -Three measurements: biomass, energy stored, carbon stored

Two Kinds of Biological Production 1.Primary Production Make their own organic matter from a source of energy and an inorganic compound Carried out by autotrophs and chemoautothrophs Ex) photosynthesis (energy “fixation”) 2. Secondary Production Cannot make their own organic compounds and therefore must feed on other living things Carried out by heterotrophs (animals, fungi, many bacteria…)

Once an organism has obtained new organic matter, it can use it to: –Make new compounds –Grow –Reproduce –Store for future use The use of energy from organic matter by most heterotrophic and autotrophic organisms is accomplished through respiration. Respiration: –the use of biomass to release energy that can be used to do work

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 over after utilization is called Net Production Net Production = Gross Production - Respiration

Equations: Production, Biomass and Energy Flow Biomass and net production –B2 = B1 + NP –NP = B2 - B1 Energy Equalities –Autotrophs NPP = GPP - R –Heterotrophs NSP = B2-B1

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 –Energy enters an ecosystem by two pathways Energy fixed by organisms Heat energy is transferred by the air or water currents or by convection through soils, sediments and warms living things

Making Energy Visible

The Laws of Thermodynamics 1 st Law of Thermodynamics - (the law of conservation of energy) -Energy is neither created nor destroyed. It is merely changed from one form to another. 2 nd Law of Thermodynamics - Energy always changes from a more useful, higher quality form to a less useful, lower quality form (heat) - energy must be added to a system in a useable form - Entropy: measure of a decrease in order 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

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 - a ecological measure of energy efficiency - the ratio of production of one trophic level to the production of the next lower trophic level - 10% transferred; 90% lost

Some Examples of Energy Flow: 1.Energy Flow in an Old-Field Food Chain - sun, autotrophs,heterotrophs 2.Energy Flow in a Stream or River -sun, algae (autotrophs) & dead organic matter, detritivores & heterotrophs 3.Energy Flow in Ocean Ecosystems -sun, autotrophs, invertebrates, whales -sun, autotrophs, invertebrates, waste/dead critters, Benthic critters 4. Chemosynthetic Energy Flow in the Ocean - chemosynthetic bacteria, heterotrophs (clams, giant worms)