Understanding Ecosystems: Structure, Function, and Cycles
An ecosystem can be defined as an open system composed of a physical-chemical part (biotope) and a biotic part (biocenosis), or all living things present in it.
Trophic Levels Within an Ecosystem
- Producers: They are the first trophic level because they are autotrophic organisms, i.e., they produce organic matter from inorganic matter and an energy source.
- Consumers: Part of the organic matter produced by producers serves as food for consumers, which is used for ATP production through cellular respiration and to reproduce and grow. Among consumers, we can distinguish several trophic levels:
- Herbivores or primary consumers
- Secondary, tertiary consumers, etc.
- Omnivores
- Scavengers and Detritivores:
- Scavengers
- Decomposers: These are essential to perform the function of recycling and biodegradation. There are two types of decomposers:
- Transformers
- Mineralizers
Food Chains and Food Webs
Food chains are very simplified representations of trophic relationships because an organism can eat individuals of various species and also be eaten by different species. Hence, a more accurate representation is the food web, which, if done comprehensively, accurately reflects trophic relationships in an ecosystem.
Biomass
Biomass is the amount of dry weight per unit area or volume of an organism or a particular trophic level.
Production
Production is the ratio between the increase of biomass and unit time.
- Types of production:
- Primary Production: Is that fixed by autotrophic organisms.
- Secondary Production: Is that for any of the other trophic levels.
- Details of production:
- Gross Production: The biomass produced per unit time by an individual or trophic level, including the one that will be consumed by respiration.
- Net Production: Gross production minus the loss by respiration.
Productivity
We define productivity as the ratio of net production and biomass. We can say that productivity is the rate at which biomass is produced, i.e., the rate at which biomass is renewed, so it is also called the renewal rate.
Efficiency
This parameter is used to express the performance of a trophic level or system and is calculated by the ratio between the energy leaving and entering.
Biogeochemical Cycles
Biogeochemical cycles, so-called because they relate to chemicals that travel through the Earth and the biosphere subsystems, are divided into two types: gaseous, such as carbon and nitrogen, and sedimentary, such as phosphorus and sulfur.
Gaseous Cycles
They possess a volatile component. They circulate through the atmosphere, hydrosphere, lithosphere, and biosphere. The movement is rapid, and lateral losses are not problematic.
- Carbon Cycle: Carbon is found in the atmosphere as CO2, in the lithosphere in the form of carbonate rocks, mainly in the hydrosphere dissolved as bicarbonate and CO2, and in the biosphere integrated into organic molecules, also as bicarbonate dissolved as carbonate skeletons and forming structures in different organisms.
- Nitrogen Cycle: Nitrogen appears in the atmosphere as N2 and to a much lesser extent in the molecules of NO, N2O, NO2, referred to generically as N2Ox.
Sedimentary Cycles
They do not possess volatile components, so they are only driven on the hydrosphere, lithosphere, and biosphere. The movement is slow, and the lateral losses are important.
- Phosphorus Cycle: Phosphorus is found in soil in the form of phosphates; it comes from rocks where it is released by chemical and mechanical weathering.
- Sulfur Cycle: Sulfur is incorporated into organic matter by plants and algae in the form of sulfate and transferred in the form of organic molecules.
Population
A population is the set of individuals of a species living in an ecosystem.
Tolerance Interval
The concept of tolerance interval: The interval of a factor within which the growth of a particular species occurs; this interval is set by the tolerances.