We explain what heterotrophic organisms are, the types that exist and how they feed. In addition, we explain what their characteristics and examples are.
What are heterotrophic organisms?
All those organisms that are heterotrophs are known as They must feed on the organic matter of other living beings. Through food they obtain the energy and resources necessary to maintain the functioning of their metabolism, grow, develop and reproduce.
Your name comes from the Greek straight“other”, and trophos“food”. They are distinguished from autotrophic organisms, capable of manufacturing their own organic matter from inorganic compounds and an external energy source (such as sunlight).
Whether they hunt other living beings, feed on their corpses, or feed on decomposing organic matter in soils, heterotrophic organisms are considered ecologically consumersThat is to say, they are incapable (in the long run) of existing in an environment devoid of other living beings that serve as a source of food in one way or another.
See also: Protozoa
Origin of heterotrophic organisms
exist Numerous theories about the beginning of life on Earth. One of them maintains that autotrophic organisms were the first since they are self-sustaining life forms.
In the extreme conditions of the forming planet, only these simple organisms could obtain energy. Only After the development of autotrophs, the existence of heterotrophs was possible.capable of taking advantage of the organic matter of the former.
However, other theories maintain the opposite. For example, Aleksandr Oparin and John Holdane suppose that during the primitive times of the planet, the formation of the first cells occurred spontaneously. These primitive cells, which Oparin called “coacervates,” would have fed on free and surrounding organic matter. There is no scientific consensus on this yet.
Types of heterotrophic organisms
Heterotrophic organisms can be classified according to their role in the food chainthat is, according to the mechanism they use to consume foreign organic matter:
- Primary consumers or herbivores. Those that feed directly on the organic matter of producers (autotrophs), as is the case with animals that consume plants, their fruits, roots or trunks.
- Secondary consumers or carnivores. Those that feed on the organic matter of primary consumers, which they hunt. There may be different links of predators between these and the end of the chain.
- Parasites. Those that consume the organic matter of the body of other living beings, causing damage but without preying on it, but existing together with it, either outside (ectoparasites) or inside (endoparasites) of its body.
- Decomposers. Those that consume dead and decomposing organic matter, that is, the remains of predators’ hunts (scavengers), the body waste of other living beings or even their excretions.
- Omnivores. Those that can consume organic matter from practically any source, whether primary or secondary consumers, decomposing organic matter, or producers.
Stages of heterotrophic nutrition
Heterotrophic nutrition can be summarized in the following stages:
- Ingestion. The organism captures another and ingests it (in whole or in part), filling its digestive cavities with its organic matter.
- Digestion. The organic matter consumed is disintegrated by various chemical reactions inside the consumer’s body, reducing it to more basic compounds that can then be assimilated.
- Metabolism. Substances extracted from organic matter and reduced to simple elements are subjected to chemical reactions. In this way, more complex molecules richer in biochemical energy are manufactured (anabolism), which are subsequently oxidized to release a greater amount of chemical energy than that invested in their manufacture (catabolism). This energy is used for the consumer’s vital processes.
- Excretion. The metabolic byproducts, along with unusable or excess organic matter, are discarded from the body, along with the gases of respiration (CO2), although through different routes: defecation (matter) and exhalation (carbon dioxide).
Feeding of heterotrophs
The specific diet of heterotrophic organisms may consist of:
- Body parts, or the entire body, of other lower heterotrophs or their offspring, whether hunted on their own or as a result of someone else’s hunt.
- Body parts of autotrophic beings, such as bacteria, plants, algae, etc.
- Fruits, shoots and other products of autotrophic beings such as plants.
- Excretions, eggs, internal substances or waste substances of other living beings.
- Organic waste accumulated in the soil and in the process of decomposition (humus).
Habitat of heterotrophic organisms
Heterotrophic organisms are found in all habitats where the number of autotrophic organisms is sufficient as food for the first link of consumers. Eventually, a second link may join that preys on them.
Although life adapts to virtually all conditions, heterotrophs They are not usually found in the most extreme conditionsFor example, only autotrophic organisms such as chemosynthetic ones can live inside volcanoes.
Ecological role
Heterotrophic organisms perform functions in an ecosystem. control and regulation of lower populations in the food pyramid. By consuming other forms of life, they help keep their numbers stable.
On the other hand, force other organisms to compete for survival. This process is called natural selection and, according to accepted and proven theories, they are the driving force of evolution and the origin of species.
However, disproportionate consumer growth can lead to imbalance. Ultimately, can lead to the extinction of the life forms consumed and then to his own.
trophic or food chain
In the trophic chain, or food chain, matter and energy It is transferred from one group of living beings to another. All living beings in an ecosystem intervene in it in different ways.
In this circuit, Each organism finds the resources to nourish itselfgrow and reproduce. Then, the energy and matter it consumed re-enters the chain, serving as food for the next link.
The food chain can be summarized as:
- Producers (autotrophs) make their own organic matter. To do this, they use inorganic matter from soils, air and water.
- Primary consumers (heterotrophs) feed on part of the organic matter from producers.
- Secondary consumers (predatory heterotrophs) feed on primary consumers to grow, develop and reproduce.
- Both primary and secondary consumers eventually perish and their organic matter is used by decomposers (detritophagous heterotrophs) that reduce it to inorganic matter in the soil.
- The producers take said inorganic matter and the cycle begins again.
More in: Food chains
Differences with autotrophs
The fundamental difference between autotrophs and heterotrophs lies in how they obtain the organic matter necessary for their biological functions (grow, develop and reproduce).
Autotrophs produce it by consuming inorganic matter. from the environment and energy from some external source. Heterotrophs cannot make organic matter from inorganic substances, and therefore must take it from other living beings.
Photoheterotrophs
Certain types of bacteria and unicellular organisms They are capable of synthesizing their own organic matter using sunlight. That is, in this sense they are similar to autotrophs.
However, they cannot get all the carbon they need from carbon dioxide, but they must also consume remains of organic matter from the environment. Therefore, they are not completely autotrophic. They are considered an intermediate category.
Examples of heterotrophic organisms
Most of the known living beings that we deal with on a daily basis are heterotrophs. To begin with, they are the the entire animal kingdom, including fish, insects, worms, mammals, birds and humans. In addition, they include fungi, decomposing bacteria, and most protozoans.