Ecosystems: Definition, Types, and Functioning

Posted on Mar 17, 2025 in Geology

Ecosystems: Definition, Components, and Interactions

An ecosystem is a partially constituted physical environment, or biotope (such as a forest, pond, or prairie), and the organisms living in it, the biocenosis (including snakes, grass, lions, etc.). These components interact through a continuous flow of energy and matter.

Biosphere and Interactions

The biosphere is the part of the planet where life exists. It is a large, integrated ecosystem encompassing all of Earth.

  • Biotope-Biocenosis Interactions: Factors in the physical environment (climate, soil, light) balance the ecosystem.
  • Biotope-Biocenosis Interactions: The characteristics of the biotope significantly impact living organisms, leading to adaptations to their environment.
  • Biocenosis Interactions: Interactions occur between organisms of the same species (intraspecific relationships) and different species (interspecific relationships).

Trophic Relationships and Levels

Trophic relationships are interactions between organisms in an ecosystem through feeding.

  • Producers: Autotrophic beings that perform photosynthesis or chemosynthesis.
  • Consumers:
    • Primary (herbivores)
    • Secondary (carnivores)
  • Decomposers: Bacteria and fungi.

A food chain is a linear representation of the energy flow in an ecosystem. In an ecosystem, food chains overlap.

There are two flows in an ecosystem: an open flow of energy and a closed flow of matter.

  • Energy Flow: Solar energy transforms into chemical energy, which is used and degraded as it passes through trophic levels, ultimately becoming thermal energy. It is unidirectional.
  • Energy Transformation: Solar energy becomes chemical energy in living beings and is released as thermal energy. Energy transfer efficiency is less than 10%.
  • Degraded Energy: Heat released by living beings circulates in the environment. Matter circulates in a closed circle in ecosystems.

Biomass and Production

Biomass is the quantity of organic matter produced. It can be used directly or indirectly to supply energy. Biofuels are fuels extracted from plants (e.g., sugar beets).

Production is the quantity of energy accumulated at different trophic levels of an ecosystem.

Biogeochemical Cycles and Ecosystem Dynamics

Biogeochemical cycles: Living things are formed by the same chemical elements as terrestrial systems. These elements follow cyclical paths.

Self-Regulation and Feedback

Self-regulation: Ecosystems have the capacity to adapt to environmental changes while continuously maintaining the normal flow of matter and energy. Feedback circuits establish a dynamic equilibrium, counteracting natural fluctuations to maintain a stable trophic structure.

Changes in the Ecosystem

Changes can be caused by:

  • Natural events (drought, flood, fire)
  • Human action (pollution, salinization, fishing, hunting)

Biological control: Reduction or elimination of a pest using biological agents, such as predators, parasitoids, organic substances (pheromones), and microorganisms.

Ecological Succession

Ecological succession is the process by which populations are replaced, creating new, more complex, and stable ecosystems.

  • Primary Succession: Occurs in a virgin biotope.
  • Secondary Succession: Occurs in an existing biological community.

Primary Succession Steps:

  1. Virgin field.
  2. Pioneering species (lichens, mosses).
  3. These species introduce changes, and plants, bushes, and lizards appear.
  4. Developmental changes allow for the establishment of other populations.
  5. Climax community: Maturity is reached with stable food chains.

Secondary Succession Steps:

  1. An ecosystem suffers alterations.
  2. Components are lost.
  3. Immature species initiate recovery.
  4. Return to the climax community.

Environmental Impacts

Soil Destruction

  • Erosion: Caused by deforestation and acid rain.
  • Degradation: Caused by pollutants or salinization.
  • Fragmentation of Territory:
    • In terrestrial ecosystems: highways, railways.
    • In river ecosystems: dams and dikes.

Contamination

Climate change, acid rain, and ozone layer destruction lead to biodiversity loss.

Forest Fires

Caused by fuel, a heat source, and fire (natural or intentional).