We explain what heterotrophic organisms are, the types that exist and how they feed. Also, what are its characteristics and examples.

heterotrophic organismheterotrophic organism
Heterotrophs need other living things as a source of food.

What are heterotrophic organisms?

Heterotrophs are all those organisms that They must feed on the organic matter of other living things.. 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 trophies“food”. They are distinguished from autotrophic organisms, capable of making their own organic matter from inorganic compounds and an external energy source (such as sunlight).

Whether they hunt other living things, feed on their carcasses, or feed on decaying organic matter in soils, heterotrophs They are considered ecologically consumers. In other words, 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 planet in formation, only these simple organisms could obtain energy. Single after the development of autotrophs, the existence of heterotrophs was possiblecapable of taking advantage of the organic matter of the former.

Nevertheless, other theories hold otherwise. 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.

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Types of heterotrophic organisms

heterotrophic organism - mosquitoheterotrophic organism - mosquito
A mosquito is a parasitic heterotroph.

Heterotrophic organisms can be classified according to their role in the food chainthat is, according to the mechanism they use to consume other people’s organic matter:

  • Primary consumers or herbivores. Those that feed directly on the organic matter of the producers (autotrophs), as occurs with animals that consume plants, their fruits, roots or trunks.
  • Secondary consumers or carnivores. Those that feed on the organic matter of primary consumers, whom 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 the hunt of predators (scavengers), the residues of the body of other living beings or even their excretions.
  • omnivores. Those that can consume organic matter from practically any source, be they 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 (totally or partially), 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. This is how more complex molecules are manufactured and richer in biochemical energy (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 vital processes of the consumer.
  • Excretion. Metabolic by-products, along with unusable or surplus organic matter, are discarded from the body, along with the gases of respiration (COtwo), although by different routes: defecation (matter) and exhalation (carbon dioxide).
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feeding of heterotrophs

heterotrophic organismheterotrophic organism
Many fungi feed on decaying organic matter.

The specific diet of heterotrophic organisms may consist of:

  • Parts of the body, or the whole body, of other lower heterotrophs or their young, whether hunted on their own or hunted by others.
  • Parts of the body 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 from other living beings.
  • Organic residues accumulated in the soil and in the process of decomposition (humus).

Habitat of heterotrophic organisms

Heterotrophic organisms are found in all habitats in which the number of autotrophic organisms is sufficient as food for the first link of consumers. Eventually, a second link may be added that preys on them.

Although life adapts to virtually all conditions, heterotrophs they are not usually found in the most extreme conditions. For example, inside volcanoes only autotrophic organisms such as chemosynthetics can live.

ecological role

heterotrophic organismheterotrophic organism
Consumers regulate the size of populations of other species.

The heterotrophic organisms exert in an ecosystem functions of control and regulation of populations lower in the food pyramid. By consuming other life forms, they help keep their numbers stable.

Secondly, force other organisms to compete for survival. This process is called natural selection and, according to accepted and proven theories, they are the engine of evolution and the origin of species.

However, a disproportionate growth of consumers can cause an imbalance. As a last resort can lead to the extinction of life forms consumed and then his own.

Trophic or food chain

In the trophic chain, or food chain, matter and energy is transferred from one group of living things to another. All living beings in an ecosystem intervene in it in different ways.

In this circuit, each organism finds the resources to nourish itself, grow and reproduce. Then the energy and matter it consumed re-enters the chain, serving as food for the next link.

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The trophic chain can be summarized in:

  • Producers (autotrophs) make their own organic matter. For this they use inorganic matter from the soil, 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

heterotrophic organismheterotrophic organism
We heterotrophs must obtain organic matter from other organisms.

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 things.

photoheterotrophs

Certain types of bacteria and single-celled organisms are capable of synthesizing their own organic matter using sunlight. That is to say that in this sense they resemble autotrophs.

Nevertheless, they cannot get all the carbon they need from carbon dioxide, but must also consume traces 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 things we deal with on a daily basis are heterotrophs. For starters, they are entire animal kingdom including fish, insects, earthworms, mammals, birds, and humans. In addition, they include fungi, spoilage bacteria, and most protozoa.

References:

  • “Heterotrophic nutrition” on Wikipedia.
  • “Autotrophic and heterotrophic organisms” in Oikos= from the National Autonomous University of Mexico.
  • “Autotrophic and heterotrophic organisms” (video) in Private Teacher Puebla.
  • “Heterotrophic organisms” (video) in SchoolBox.
  • “Heterotroph” in The Encyclopaedia Britannica.

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