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11.3.1. Energy and matter in ecosystems

Energy and matter in ecosystems

The planet Earth is a large system in which there is an exchange of matter and energy between its components (inert, such as soilwater, etc., and living beings) and, when a change occurs, if it is not too drastic, you can re-establish a balance between its components.

Solar energy is used by autotrophic photosynthetic beings to perform photosynthesis and create organic matter that passes to other living beings, but solar energy is also the generator of winds, climate, sea currents, etc.

An ecosystem has a similar structure. Relationships are established between its components of exchange of matter and energy, since all living beings need matter to be able to grow and renew the tissues that wear out, and energy to be able to carry out their vital functions.

Autotrophic beings, plants, through photosynthesis are capable of forming organic matter (carbohydrates) from inorganic matter (water, carbon dioxide, mineral salts) using the energy of the sun. For this reason, these organisms are called producers of the ecosystem and are the basis of the diet of the rest of living beings.

Animals are heterotrophs, and we need the organic matter made (and the energy it contains) by producers (autotrophs) or other heterotrophs. Therefore, within the ecosystem, we are consumers.

Finally, decomposers and disintegrators transform organic matter into inorganic matter and close the cycle of matter.

There is a flow of energy from producers to decomposers, passing through all trophic levels. It is a linear flow in which energy (from the sun) can only be used once, passing to heterotrophs via food to enable them to perform their life functions.

Flujo de la energía y ciclo de materia en un ecosistema

Flujo de energía en un ecosistema

Matter passes from one organism to another, but when it dies or produces waste, the matter can be used again by plants thanks to the action of decomposers. The cycle of matter causes the same matter to pass from one organism to another.

Trophic levels

The following trophic levels are distinguished in an ecosystem:

  • Producers: They are the autotrophic photosynthetic organisms, the first link in the food chain. They transform the energy of sunlight into chemical energy, which is stored in the organic matter they produce through photosynthesis. They are plants and algae.
  • Consumers: they are heterotrophic organisms, that is, they obtain their energy from food (organic matter) produced by other organisms. Some of the energy they receive is lost through cellular respiration.
    • Primary consumers: they feed on the  producing organisms, such as plants or algaeThey are herbivorous animals , and constitute the second link in the food chain.
    • Secondary consumers: they feed on herbivorous animals (primary consumers). They are the first order carnivores and constitute the third link in the food chain.
    • Tertiary consumers: They feed on other carnivorous animals. They are second-order carnivores and constitute the fourth link in the food chain.
  • Decomposersdegrade and break down organic matter and transform it into inorganic matter, much simpler and more usable by producing organisms. They are thelast linkin the food chain, those that close the cycle of matter. Fungi and bacteria are decomposers.

Trophic relationships in the ecosystem

Trophic or feeding relationships are the relationships of food dependence that are established between the different trophic levels of an ecosystem.

Organisms at one trophic level obtain matter and energy from organisms at a lower trophic level.

Two types of trophic relationships are distinguished:

Trophic chains

The food chain represents how matter and energy are transferred between organisms in an ecosystem. That is, what organisms does an organism feed on and what other living beings does it serve as food? It is a linear sequence in which, by means of arrows, it is indicated how matter and energy (food) pass from one organism to another.

The number of links in a food chain can vary depending on the ecosystem, although it is usually quite small, since at each step there is a significant loss of energy.

Cadena trófica

Tomada de Wikipedia, de chris (through works of J. Patrick Fischer, C. Schuhmacher, Madprime, Luis Fernández García, Luis Miguel Bugallo Sánchez, chung-tung yeh, Susanne Heyer and Simon Andrews)

Interactive activity: Complete the food chains.

Interactive activity: Trophic chains.

Trophic netwoks

But the food chain is too simple a representation, it is only a line, and a species does not feed exclusively on another species, but rather the diet is more varied and many different food chains are established.

species can be consumed by many types of organisms and feed on several different species. For this reason, more than trophic chains, in ecosystems there are trophic networks, a set of related trophic chains that represent all the feeding relationships that occur between the organisms of an ecosystem.

Red trófica

By Matthew C. Perry [Public domain or Public domain], via Wikimedia Commons

Interactive activity: Trophic networks.

Trophic pyramids

The trophic relationships of an ecosystem can also be represented using pyramids. At the base of the trophic pyramid are the producers, and above them, the primary consumers (herbivores), and above these, the secondary and tertiary consumers (carnivores), but in increasingly smaller quantities. The decomposers are outside the pyramid, since they act on the remains of all living things.

Niveles tróficos de un ecosistema

By Roddelgado (Own work) [CC BY-SA 4.0], via Wikimedia Commons 


Answer in your notebook

Why are decomposers so important?

Answer in your notebook

What trophic level is responsible for transforming the energy of the Sun into useful energy for the rest of the living beings in the ecosystem?