Ecology: Trophic Transfer of Energy in an Ecosystem
Updated on April 30, 2015 from
What is an Ecosystem?
Ecology, the study of the interactions of living organisms with one another and with their
environment, is the study of ecosystems, an ecological system encompassing a community and
all the physical aspects of its habitat.
A place where a certain species lives is called its habitat, and groups of different species living
together are called a community. All of the biotic and abiotic aspects of a community are called
an ecosystem. Ecosystems run on energy, which comes in from the sun. Life is possible
because photosynthesis captures the light energy from the sun and turns it into the chemical
energy of organic molecules. This is a basic principle in ecology. The organic molecule
compounds are composed of what we call food, which gives us energy.
Where Do Organisms Get Energy From?
An organism acquires energy from the food it eats. Some of that energy is stored as fat, some is
lost through wastes, urine, and feces. But most escapes as heat, which is produced when energy
is transferred from one form to another. Only 10% of energy if incorporated into the next trophic
level, so because the loss of energy from one level to the next is so great, the number of trophic
levels is limited.
The Energy Pyramid
Energy Flow in an Ecosystem
Energy transfer in an ecosystem, pyramid model
Source: Stephsnature
Energy flows through food webs, a network
of feeding relationships in an environment,
which contain food chains, a linear pathway
of energy transfer in an ecosystem. Food
chains are composed of trophic levels: a
group of organisms that have the same
source of energy. The Energy Pyramid is a
model that shows how energy flows through
a food chain. Producers form the base of the
pyramid and help support all other
organisms. Animals that consume the
producers (primary consumers) occupy the
next level. Consumers do not absorb all the
energy stored in their food. In addition, they
use some of this energy when they perform
daily activities and lose energy in the form
of heat. Only about 10 percent of the energy
from each level of an energy pyramid is
available to organisms in the next level.
Transfer of Energy
Numbers of Organisms:
In any food web, energy is lost each time one organism eats another. Because of this, there have to be many
more plants than there are plant-eaters. There are more autotrophs than heterotrophs, and more plant-eaters than
meat-eaters. Although there is intense competition between animals, there is also an interdependence. When the
population of one species decreases, it can affect an entire chain of other species and have unpredictable
consequences.
Equilibrium
As the number of carnivores in a community increases, they eat more and more of the herbivores, decreasing
the herbivore population. It then becomes harder and harder for the carnivores to find herbivores to eat, and the
population of carnivores decreases as they compete for food. In this way, the carnivores and herbivores stay in a
relatively stable equilibrium, each limiting the other's population. A similar equilibrium exists between
producers and consumers.
BIOMASS PYRAMID
Diagram of the transfer of energy and heat loss in an ecosystem
Answer the following questions:
Name: ________________
1. According to the image above, which level has the most energy available to them? EXPLAIN you answer.
2. What happens to the amount of energy as you move up each level of the energy pyramid? Explain your thinking.
3. How is the energy lost from each energy level?
4. What happens to the sizes of populations as you move up each level of the energy pyramid? Explain your
thinking.
5. Using the energy pyramid model, explain why there are fewer third-level consumers than primary consumers.
6. What would happen to the energy in the energy pyramid if a disease destroyed half of the primary consumers?
7. If a drought destroys half of the producers in an energy pyramid, what will happen to the other levels of the
energy pyramid? (Consider the role of competition in your response).