Ecological Interactions

Interactions within Species and with Other Species

Types of Ecological Interactions

1. How are ecological interactions classified?

Ecological interactions are classified as intraspecific or interspecific interactions and as harmonious or inharmonious interactions.

Ecological Interactions - Biology Questions and Answers

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2. What are intraspecific and interspecific ecological interactions?

Intraspecific ecological interactions are those between individuals of the same species. Interspecific ecological interactions are ecological interactions between individuals of different species. 

3. What is an inharmonious ecological interaction?

An inharmonious, or negative, ecological interaction is when at least one of the participating organisms is harmed.

4. What is harmonious ecological interaction?

An harmonious, or positive, ecological interaction is when none of the participating organisms is harmed.

Intraspecific Ecological Interactions

5. What are the main intraspecific ecological interactions?

The main harmonious intraspecific ecological interactions are colonies and societies. The main inharmonious intraspecific ecological interactions are intraspecific competition and cannibalism.

6. What are colonies and societies?

Colonies are functional integrated aggregates formed by individuals of the same species. Colonies are often confused with a single individual. Examples are coral reefs, by-the-wind sailors and filamentous algae.

Societies are interactions for labor division and collaboration among individuals of the same species. Human societies are examples of ecological societies; other species, such as bees, ants, termites, wolves and dolphins, also form societies.

7. What is competition? Which type of ecological interaction is competition?

Competition is the ecological interaction in which individuals explore the same ecological niche or their ecological niches partially coincide and, therefore, competition for the same environmental resources takes place.

Competition is harmful for all participating organisms and is therefore classified as an inharmonious (negative) ecological interaction. 

8. What is an example of intraspecific competition?

Intraspecific competition occurs in practically all species, for example, the competition of humans for a job.

9. Why is cannibalism an inharmonious intraspecific ecological interaction?

In cannibalism, an individual eats others of the same species (this occurs in some insects and arachnids). Since it is an interaction between organisms of the same species and at least one of them is harmed (the other benefits), the classification as inharmonious intraspecific ecological interaction is justified.

  • Ecological Interactions Review - Image Diversity: cannibalism

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Interspecific Ecological Interactions

10. What are the main interspecific ecological interactions?

The main harmonious interspecific ecological interactions are: protocooperation, mutualism and commensalism. The main inharmonious interspecific ecological interactions are: interspecific competition, parasitism, predatism and ammensalism.

11. What is protocooperation?

Protocooperation is the ecological interaction in which both participants benefit but which is not obligatory for their survival. Protocooperation is a harmonious (positive) interspecific ecological interaction. Examples of protocooperation are: the spur-winged plover, which eats residues from crocodile teeth by using its beak; the removal of ectoparasites from the back of bovines by some birds that eat the parasites; and the hermit crab, which live inside shells on top of which sea anemones live (these offer protection to the crab and gain mobility to obtain food).

12. What is mutualism?

Mutualism is the ecological interaction in which both participants benefit and which is obligatory for their survival. Mutualism is a harmonious (positive) ecological interaction. Mutualism is also known as symbiosis. Examples of mutualism are: the association between microorganisms that digest cellulose and the ruminants or insects within which they live; lichens, formed by algae or cyanobacteria that produce organic material for the fungi and absorb water with their help; and nitrifying bacteria of the genus Rhizobium, that when attached to leguminous plants offers nitrogen to these plants.

  • Ecological Interactions Review - Image Diversity: mutualism

13. What is commensalism?

Commensalism is the ecological interaction in which one individual benefits while the other is neither benefits nor is harmed. Commensalism is a harmonious (positive) ecological interaction, since none of the participants is harmed. An example of commensalism is the numerous bacteria that live on the skin and in the digestive tract of humans without being pathogenic or beneficial. They are innocuous bacteria living in commensalism with humans.

  • Ecological Interactions Review - Image Diversity: commensalism

14. What benefits can commensalism offer to a species?

Commensalism may involve the obtainment of food (for example, the innocuous bacteria of the human gut), shelter or support (epiphytes on trees) and transportation (pollen carried by insects or birds). The commensalism that involves the obtainment of shelter is also called inquilinism.

15. What are some examples of interspecific competition?

Examples of interspecific competition are: disputes among vultures, worms, flies and microorganisms for carrion and the competition between snakes and eagles for rodents.

16. What is parasitism?

Parasitism is the ecological interaction in which an organism lives at the expense of another. The parasite often does not cause the immediate death of the host since it needs the host alive to survive.

Parasitism is an inharmonious (negative) interspecific ecological interaction, since one participant is harmed while the other benefits.

  • Ecological Interactions Review - Image Diversity: parasitism

17. What are some examples of parasitism?

Classical examples are the parasites of humans (host), such as the trypanosome that causes Chagas’ disease, the HIV virus (AIDS), the bacteria that cause tuberculosis, the schistosome that causes schistosomiasis, hookworms, etc. Other examples are: trees (host) and parasitic helminthes (parasite), dogs (host) and lice (parasite), cattle (host) and ticks (parasite), etc.

18. What is predatism?

Predatism is the ecological interaction in which one individual mutilates or kills another to get food. Predatism is an inharmonious (negative) ecological interaction since one participant is harmed.

  • Ecological Interactions Review - Image Diversity: predatism

19. Is herbivorism a form of predatism?

Herbivorism is a form of predatism in which first order consumers feed on producers (plants or algae). For example, the relationship between birds and fruits, humans and edible vegetables, etc. are forms of predatism. (There are proposals to consider the herbivorism of leaves a form of parasitism and the herbivorism of entire plants and seeds a form of predatism).

20. What is ammensalim?

Ammensalism is the ecological interaction in which an individual harms another without obtaining benefit. Ammensalism is an inharmonious (negative) ecological interaction since one participant is harmed.

(Sometimes it is wrongly said that ammensalism is a form of ecological interaction in which an organism releases substances that harm another species in the environment; this situation is indeed an example of ammensalim but the concept is not restricted to it.)

One of the best examples of ammensalism is between humans and other species under threat of extinction due to human actions such as habitat devastation by fires, ecological accidents, leisure hunting, etc. Another example is the red tide, a proliferation of algae that can lead to death by intoxication of fish and other animals.

  • Ecological Interactions Review - Image Diversity: ammensalism

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