Answer to Question #2387 in Biochemistry for Mary

Question

The rule of thumb concerning ecosystems as units that capture energy and transport it is as follows: For every jump in trophic level, the amount of available energy drops by 90%. Discuss in detail what accounts for this loss of energy? Please give examples

Answer 1

It means that living organisms of the next trophic level utilize only 10% of
the food from previous level (due to the laws of thermodynamics), 90% is
lost as unmetabolized molecules.
Thus 1 pound of carnivore (lion) requires
10 pounds of herbivores (cows) or 100 pound of plants.
The producers in an ecosystem are plants and other organisms that undergo
photosynthesis.
Organisms that eat plants are called consumers. Trophic
levels (eating levels) begin with producers. Producers form their first
trophic level. Consumers form several additional levels. As you move up
through the trophic levels, more energy is lost. This pattern of energy
reduction is repeated as you move up each successive trophic level.
In fact,
as you ascend the levels, reduction becomes even more severe because warm
blooded animals must maintain a constant body heat. Producing heat is energy
lost. The rule of thumb is as follows: for every jump in trophic level, the
amount of available energy drops by 90%.
What is the consequence of this
energy reduction at each trophic level? First, this is the reason that large
animals tend to be rare. For example, if you have a field that contains 100
mice, how many weasels could that field support? Remember, at most, only 10%
of energy is passed on to the next level. Therefore, far fewer weasels could
make a living off of this field of mice. The number of larger animals that
would prey on the weasels would be even fewer, and so on and so on. In
summary, as each trophic level is ascended, the amount of available energy
drops by 90%. Very little of the original solar energy assimilated by plants
is available to the animals in the higher trophic levels. It is either
dissipated as heat or used by photosynthesizing organisms to power their own
physical processes.