Relationships between organisms in ecosystem – food (trophic) chains

The basic feature of living organisms is (among other things) the constant transformation of energy, matter and information, which takes place in the so-called ecosystems (basic functional unit of living nature, consisting of organic and inorganic matter). Each ecosystem consists of three groups of organisms:

PRODUCERS – especially green plants that convert energy from solar radiation into energy of organic bonds in the process of photosynthesis – are the primary producers of organic matter in the ecosystem.

CONSUMERS – part of the organic substances that produce green plants represents food for heterotrophic organisms (animals). Some consumers represent food for other consumers and those for other (higher) – this is how food chain is formed. According to the position of consumers in the food chains we distinguish between:
Herbivores – first order consumers who feed on plant food;
Carnivore and omnivore – higher order consumers. Carnivores include beasts – predators. Omnivores feed on both plant and animal food (e.g. humans)

REDUCENTS – decompose dead bodies of plants and animals into inorganic substances. We include saprophytic organisms (fungi, bacteria) that close the circulation of substances in the ecosystem.

Pic 107: Food chain


The energy cycle in the ecosystem consists of the uptake of nutrients in inorganic form by plants (in the form of ions dissolved in water) and their subsequent storage in biomass. Through the food chain, the elements enter the soil – through dead plant and animal bodies and their excrements, where reducers (decomposers) enter this cycle. Their task is to break down these residues down to inorganic substances that take up plants through the root systems. As part of this decomposition, some elements may also enter the atmosphere (eg sulfur and nitrogen).


It is a process of oxidation of organic substances, which includes their mineralization, especially with the participation of bacteria, saprophages (a heterotrophic organism that extracts energy from organic substances of dead organisms), microorganisms and fungi.

Mushrooms have been involved in recycling for about 400 million years. Unlike bacteria, fungi remain metabolically active during the winter (for example, they can “moldy” bread in the freezer). Any bio-waste can be used in the compost. However, waste from animal production is not recommended for (inter alia) hygiene reasons for composting.

Humidity and ambient temperature and air access (an aerobic process) are important for composting. A suitable humidity is in the range of 45–60%, no more, as the compost starts to rot. At lower humidity, the process slows down. The optimum temperature is in the range of 40–65 °C. A temperature of 50 °C is required to destroy pathogens. The compost is stored either in a container (wood, concrete, stone, etc.) or in a so-called graves (stacks).

Suitable composting wastes include garden waste (mown grass, fallen fruit, withered flowers), kitchens (plant food residues – scales, cuttings, etc.) and biological waste from livestock farming (herbivores). The compost should not be put arbitrarily – the principle of mixing nitrogenous raw materials (soft, fleshy, green – e.g. plant cuttings) with carbon (hard, firm, dark – e.g. dry leaves, sawdust) applies. The optimum ratio is about 35: 1 (C: N), while it is important to mix the ingredients.

There are two stages in composting

Oxidation stage (consumption of O2 and organic matter; formation of CO2 and NH3 ) – bacteria and fungi degrade simple carbohydrates, amino acids and proteins, increasing temperature. Microorganisms degrade lipids and complex carbohydrates. At the same time, pathogens are destroyed and temperature is reduced again.

Ageing stage: humification occurs – a product with a lower carbon to nitrogen ratio is produced.

Food chains

In terms of the use of living or dead organic matter we recognize two basic kinds of a food chain:

Grazing food chain, starting with organic matter created by autotrophic plants. This type of food chain starts from the living green plants goes to grazing herbivores, and on to carnivores. Ecosystems with such type of food chain are directly dependent on an influx of solar radiation. This type of chain thus depends on autotrophic energy capture and the movement of this captured energy to herbivores. Most of the ecosystems in nature follow this type of food chain. The phytoplankton →zooplankton →fish sequence or the grasses →rabbit →fox sequences are the examples, of grazing food chain.

Detritus food chain, which is formed by reducers. The decomposition product of one group of decomposers becomes a substrate for another group of decomposers, resulting in mineralization of dead bodies. This type of food chain goes from dead organic matter into mi¬croorganisms and then to organisms feeding on detritus (detrivores) and their predators. Such ecosystems are thus less dependent on direct solar energy. These depend chiefly on the influx of organic matter produced in another system. For example, such type of food chain operates in the decomposing accumulated litter in a temperate forest.

An animal that feeds on only one kind of food and cannot take another kind of food is referred to as a monophage (e.g. silkworm caterpillars feed only on mulberry leaves). Conversely, an animal that can also accept another kind of food is called a polyphage.

Relations between animals

Relations between animals may be:

A) indifferent (so called neutralism) – species (populations – individuals of one species that share a common opinion at the same time) are independent of each other;

B) negative, which may be of varying intensity:

competition – populations compete for space or food source;
parasitism – a parasite (one population) lives at the expense of a host (another population). Ectoparasite lives on the body surface of another animal and the endoparasite lives inside the body of another animal;
predation – one population feeds on the other (predator-prey);

C) positive – populations are mutually beneficial:

commensalism – free coexistence of populations, e.g. large beasts and vultures that feed on their prey;
mutualism – a more solid form of coexistence; e.g. nitrogenous bacteria form tubers on the roots of bean plants where they live. Bacteria provide plants with a useful form of nitrogen;
symbiosis – the strongest form of coexistence, e.g. lichens (fungus + algae or cyanobacteria).