Biological Productivity
and Energy Flow
Biological Production

 Biomass
- The total amount of organic matter on Earth or in any
ecosystem.
 Biological Production
- The capture of usable energy from the environment to
produce organic compounds in which that energy in
stored.
6CO2 + 6H2O→C6H12O6 + 6O2
Sounds like
photosynthesis!
Two Kinds of Biological
Production
1. Primary Production


Make their own organic matter from a source of energy
(sun) and an inorganic compound (water)
 Carried out by autotrophs and chemoautotrophs
 Ex: photosynthesis
2. Secondary Production

Cannot make their own organic compounds
and therefore must feed on other living things
 Carried out by heterotrophs
 The use of energy from organic matter (stuff
you eat) 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
C6H12O6 + 6O2 → 6CO2 + 6H2O
Why are
decomposers
(aka “recyclers”)
so important?
Gross and Net Production

 The production of biomass and it’s use as a source of
energy by autotrophs includes three steps:
1.
2.
3.
Gross Production: An organism produces organic matter within it’s
body (ex. Proteins & Sugars)
It uses some of this new organic matter as a fuel in respiration
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
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 to a less useful, lower quality form
Which law of
thermodynamics
is Bob using?

• 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
*how much goes in vs. how much is used
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
Some Example of Energy Flow:
 Energy Flow in an Old-Field Food Chain
 Energy Flow in a Stream or River
 Energy Flow in Ocean Ecosystems
 Chemosynthetic Energy Flow in the Ocean