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Chapter 4
Organisation at the
Ecosystem Level
4.1 ENERGY FLOW IN THE ECOSYSTEM
Energy flow represents a fundamental ecological concept with a unifying role among the partial plant, animal, and microorganism studies. It is
based on trophic relations between various organisms and constitutes the
“ driving force” for the function of the ecosystem. Energy flow is not circular
but linear (Figure 4.1), with a direction from the lower to the higher trophic
levels and with conversion from light to chemical energy and, finally, from
chemical energy to heat, i.e. to a downgraded energy form. Energy flow
interruption in an ecosystem entails the collapse of its organization; the
ecosystem is gradually decomposed into inorganic matter.
The energy source for the biosphere is solar radiation. Only a few special
deep sea ecosystems represent exceptions, since these can obtain energy
from chemical substances without the presence of light. The manifold
life manifestations depend on light for energy. Plants and algae and some
bacteria bind and exploit light energy through photosynthesis.
Solar radiation with intensity 0–1.2 cal/min/cm 2 reaches the planet
Earth. The main part of this energy mobilizes wind, wave and oceanic
current mechanisms as well as the hydrological cycle, ultimately returning
to space as infrared radiation. It is estimated that around 1% of the total
incident radiation is bound by the biosphere through photosynthesis.
Two essential concepts used for the study of energy flow in an ecosystem
are biomass and production. Biomass is defined as the energy content
(or the equivalent organic matter content) of an organism, population or
ecosystem. Production is the amount of biomass increase, while productivity
is production per time period. Biomass and production are measured, as a
rule, in energy units (e.g. calories) or mass units (e.g. grams). Productivity
is usually expressed in mass units per time and surface.
Other useful concepts are consumption, assimilation, waste and respiration, which are measured by the same units. Hence, trophic relationships are
analysed as follows: the biomass deducted from a prey population, i.e. from
an inferior trophic level, serves as consumption to a predator population,
DOI: 10.1201/b14609-4
Chapter 4
Organisation at the
Ecosystem Level
4.1 ENERGY FLOW IN THE ECOSYSTEM
Energy flow represents a fundamental ecological concept with a unifying role among the partial plant, animal, and microorganism studies. It is
based on trophic relations between various organisms and constitutes the
“ driving force” for the function of the ecosystem. Energy flow is not circular
but linear (Figure 4.1), with a direction from the lower to the higher trophic
levels and with conversion from light to chemical energy and, finally, from
chemical energy to heat, i.e. to a downgraded energy form. Energy flow
interruption in an ecosystem entails the collapse of its organization; the
ecosystem is gradually decomposed into inorganic matter.
The energy source for the biosphere is solar radiation. Only a few special
deep sea ecosystems represent exceptions, since these can obtain energy
from chemical substances without the presence of light. The manifold
life manifestations depend on light for energy. Plants and algae and some
bacteria bind and exploit light energy through photosynthesis.
Solar radiation with intensity 0–1.2 cal/min/cm 2 reaches the planet
Earth. The main part of this energy mobilizes wind, wave and oceanic
current mechanisms as well as the hydrological cycle, ultimately returning
to space as infrared radiation. It is estimated that around 1% of the total
incident radiation is bound by the biosphere through photosynthesis.
Two essential concepts used for the study of energy flow in an ecosystem
are biomass and production. Biomass is defined as the energy content
(or the equivalent organic matter content) of an organism, population or
ecosystem. Production is the amount of biomass increase, while productivity
is production per time period. Biomass and production are measured, as a
rule, in energy units (e.g. calories) or mass units (e.g. grams). Productivity
is usually expressed in mass units per time and surface.
Other useful concepts are consumption, assimilation, waste and respiration, which are measured by the same units. Hence, trophic relationships are
analysed as follows: the biomass deducted from a prey population, i.e. from
an inferior trophic level, serves as consumption to a predator population,
DOI: 10.1201/b14609-4