To achieve an accurate definition of the concept of heterotrophic organisms it is necessary to establish the meaning of the two terms that compose it.
A organism, at the biological level, is the set of organs They interact according to the laws of nature. Extensively to this meaning, organism can be used as a synonym for living being.
Heterotroph, meanwhile, is a adjective which applies to the living being that cannot take an inorganic substance and create organic matter for itself, forcing it to feed on other living beings.
The heterotrophic organisms, therefore, are those who They feed on other organisms to obtain organic matter already synthesized because they do not have an independent food production system. This means that obtaining Energy, nitrogen and carbon they achieve it from feeding on other living beings.
All the animals and the mushrooms they are part of the set of heterotrophic organisms. This characteristic of their nutrition makes heterotrophs always depend on another living being for their subsistence, since they obtain their energy from an external source of organic matter.
Most heterotrophic organisms are chemoganotrophs and they use the energy that they extract directly from organic substances. A few heterotrophic organisms are part of the subset of the photoorganotrophs, which manage to fix the energy coming from the light.
If the organism, on the other hand, is able to generate its food through an inorganic substance, it is classified as autotroph. An example of an autotrophic organism are the plants, which produce the energy they need by being in contact with light and combining it with the carbon dioxide in the air and the minerals in the soil are capable of producing their own energy.
Many heterotrophic organisms (such as a cow) feed on autotrophic organisms (the alfalfa). However, many times it can happen that a heterotrophic organism (such as a Lion) feeds on another organism with the same characteristics (such as a zebra).
Fungi, heterotrophic organisms of various characteristics
Although generally when speaking of heterotrophic organisms, animals are mentioned; being easy to understand because it is one of the characteristics that clearly differentiate us from plants. However, within this group there is also the group of fungis, mushrooms.
Unlike plants, fungi do not have chlorophyll so they cannot develop their own food from the energy of light and substances in the soil (photosynthesis); for this reason they are located within the classification of heterotrophic organisms. There are several classifications within the world of heterotrophic fungi.
The Saprobes They feed on dead organic matter, of animal and plant origin. Within this group are the obligate saprobes that can feed only in this way and the facultative ones that can vary their feeding depending on the possibilities of the environment.
The Parasites they feed on the living tissue of other living beings. They settle in the bark of plants and damage their tissues. Its action causes rot in plants causing serious consequences. Some of these fungi can also attack animals.
The Symbiotes they join with other living beings and establish a bond in which each one obtains a benefit. It is an associative relationship that occurs, for example, between a fungus and an alga: the fungus extracts nutrients from it and provides protection against possible enemies. In some cases, they can even develop combined forms of reproduction.
Having said all this and taking into account the many differences that a fungus represents from an animal that can move, we can say that within the variety of heterotrophic organisms we can find species that are absolutely different from each other but that share one thing: an energy-based diet that other organisms have synthesized.