Ecosystems maintain themselves from the flow of energy through different trophic levels in an ecosystem. The cycling energy and nutrients obtained from different external sources sustain the ecosystem. Energy flow is depicted by the use of food chains, food webs, and ecological pyramids
In an ecosystem, there exist, several feeding groups, each known as a trophic level into which producers and consumers can be arranged. Producers represent the first trophic level, herbivores the second, primary carnivores, the third and top carnivores represent the fourth.
A food chain refers to energy transfer and nutrients transfer from organism to another in an ecosystem by the repeated process of eating and being eaten. The initial link in a food chain is a producer, often a green plant that produces energy for consumers. Plants capture solar energy and convert it into chemical energy stored in the form of fats, proteins, or carbohydrates. They and herbivores utilize the stored food in plants. Herbivores are then preyed on by some carnivorous animals. Food from one trophic level is therefore distributed to the other trophic level establishing a food chain.
Grass Mouse Snake Hawk
There are three types of food chains;
- Grazing food chain: This starts from producers to primary consumers, to secondary consumers, then tertiary consumers. Green plants may be oxidized in respiration, eaten by herbivores or die and decay. Food assimilated in herbivores can be stored as proteins, carbohydrates, or fats and transformed into complex organic molecules. Carnivores may then consume the energy or die and decay for consumption by decomposers.
- Parasitic food Chain: The energy in this food chain goes from large organisms to smaller ones.
- Detritus food chain: Detritus refers to dead organic remains from the grazing food chain. This energy is a source for organisms referred to as detritivores that are not part of the grazing food chain. Organisms in this food chain include fungi, bacteria, and algae.
Many food chains exist, but they are not independent. An organism does not depend solely on another, but resources are shared among various microorganisms, for example, animals may be eaten by several predators. Interlinks between the food chains form a food web which maintains the stability of the ecosystem due to the formation of alternative pathways.
An ecological pyramid can be used to show the trophic structure of an ecosystem. At each step, energy is lost as heat; thus, organisms pass lesser energy to the next trophic level than they receive. There are different types of ecological pyramids
- Pyramid of numbers: This pyramid depicts the numbers of producers and consumers in an ecosystem. The base represents producers which are the most abundant and the number of organisms goes decreasing up the pyramid. This pyramid indicates that fewer consumers consume producers.
- Pyramid of biomass: This pyramid is formed by the weights or biomass of the members of a food chain. It indicates the total weight and fixed energy present at one time and the decrease of biomass in each tropic level. The biomass of the organisms decreases up the pyramid.
- Pyramid of energy: It depicts the total amount of energy at each trophic level and the role of various organisms in the transfer of energy. The energy at the producer level will be more than the energy at higher trophic levels.