Unit 6: The structure of the ecosystems                      1   2   3   4   5   6

5. Matter and energy in the ecosystem

In ecosystems, matter and energy are transmitted though the food relationships between organisms. However, matter and energy behave in a different way. While energy enters, flows through the ecosystem in one way and finally is lost, matter describe a cycle, passing from a trophic level to other and it never losses.

a) Flow of energy trough the ecosystem

Energy enters to the ecosystem during photosynthesis. Thanks to this reaction producers transform the electromagnetic energy of sunlight into chemical energy that is stored in the chemical bonds of organic matter. In this way, energy can pass from a trophic level to another. Consumers obtain the energy from the food they eat and decomposers from the organic matter they decompose.

Producers, consumers and decomposers, use:

- A part of the energy to make their own bodies (to repair tissues and to grow).

- Other part is used to perform vital functions and to stay alive (movement, breathing, etc).

- Other part is lost as heat.

Only the energy stored in the tissues can pass to the following trophic level.

The energy flows in one direction through the ecosystem and it is finally lost.

b) Cycle of matter in the ecosystem

Matter flows through the ecosystem describing a cycle.

Producers take in inorganic matter form the environment, changing it into organic matter. Consumers obtain this organic matter from producers and other consumers by eating. Finally organic matter finishes in the decomposers’ level where it is transformed into inorganic matter. That is how it is returned to the inert environment and put at disposal of producers again.

Matter flows in a closed cycle trough the ecosystem. It does not lose and can be reused many times.

5.1. What is the difference between the behavior of matter and energy

        in the ecosystems?

5.2. Why it is said that decomposers close the cycle of matter in the

        ecosystem?

5.3. A trophic pyramid is a way to represent graphically the amount of matter

        or energy that exists in each trophic level in an ecosystem.

        If you observe the example, each level stores less energy

        than the previous one. Could you give an explanation to this?