Understanding Food Chains and Biogeochemical Cycles
Chain: An object consisting of a series of links.
Trophic: Directly related to food.
Food: Any substance (solid or liquid) usually ingested by living organisms for nutritional and psychological purposes.
What is a Food Chain?
Food chain comes from the Greek word throphe, meaning food. It is the process of energy transfer through a range of organisms.
Definition of a food chain: A food chain is the process of transferring food energy through a series of organisms, in which each feeds on the preceding one and becomes food for the following one. The food chain, also known as the trophic chain, is the flow of energy and nutrients that is established between the different species in an ecosystem in relation to their nutrition.
Each chain starts with a vegetable organism, or an autotrophic primary producer, which is an organism that makes its own food.
Examples of Food Chains
Freshwater food chains:
- Algae and aquatic plants
- Herbivorous fish
- Carnivorous fish
At sea: At this stage, things are a bit more complicated and diversified.
- Dissolved salts
- Phytoplankton (photosynthesis)
- Zooplankton
- Larger fish
Wastes from different consumption levels fall to the bottom of the sea where saprophytic bacteria (which feed on decaying organic matter) convert them into minerals. These minerals become salts that are used to restart the process.
In the sea, because “the big fish eats the small,” we can find seven or even more links (up to five more compared to what can be found on land).
Nutrient Cycling and Biogeochemical Cycles
- Nutrient Cycle: Designates the cyclical journey of a substance or nutrient essential for life through the physical and biological environment.
- All organisms participate in the various trophic levels.
- The most important cycles are the carbon, nitrogen, phosphorus, water, oxygen, and sulfur cycles.
- The inorganic nutrient cycle goes through organisms, air, water, and even rock. Chemical cycles pass through biological and geological cycles (biogeochemical cycles).
- When cycles occur naturally without external input, the ecosystem is said to be in equilibrium.
- Human activities release elements, altering the balance of the stages of the biogeochemical cycles.
Heavy Metal Cycles
What is a heavy metal? Any metallic chemical element that has a density at least five times greater than that of water and is also toxic or poisonous at low concentrations.
What is a cycle? A cycle is a set of steps that repeat again and again. A cycle does not end; it has no beginning, it’s like a circle. Cycles in nature occur continuously.
Heavy metals are not chemically or biologically degradable. Once released, they can remain in the environment for hundreds of years. In addition, their concentration increases in living organisms as they are eaten by others, so that eating contaminated plants or animals can cause symptoms of intoxication.
They can be found in greater amounts in the deeper layers of rivers and to a lesser extent on the surface.
The toxicity of heavy metals is based on a variety of ways they influence the physiological processes of organisms.