Predation, parasitism, competition… all living beings, besides interacting with the environment, we relate to other living beings. What types of relationships in addition to those you know? Do you feel like to know them?
INTRODUCTION
The group of all living beings in an ecosystem is called biocenosis or community. The biocenosis is formed in turn by different populations, which would be the set of individuals of the same species occupying an area. For survival, it is imperative that relations between them are established, sometimes beneficial and sometimes harmful.
INTERESPECIFIC RELATIONSHIPS
They are those that occur between individuals of different species. This interaction it is called symbiosis. Symbiotic relationships can be beneficial to a species, both, or harmful to one of the two.
Detrimental to all the species involved:
• Competition: occurs when one or more resources are limiting (food, land, light, soil …). This relationship is very important in evolution, as it allows natural selection acts by promoting the survival and reproduction of the most successful species according to their physiology, behavior …
One species has benefits and the other is detrimented:
- Predation: occurs when one species (predator) feeds on another (prey). This is the case of cats, wolves, sharks …
- Parasitism: one species (parasite) lives at the expense of other (host) and causes it injury. Fleas, ticks, pathogenic bacteria… are the best known, but there are also vertebrate parasites, like the cuckoo that lay their eggs in the nests of other birds, which will raise their chicks (brood parasitism). Especially interesting are the “zombie parasites”, which modify the behavior of the host. Read this post to learn more!
Reed warbler (Acrocephalus scirpaceus) feeding a cuckoo’s chick (Cuculus canorus). Photo by Harald Olsen Parasites that live inside the host’s body are called endoparasites (such as tapeworms), and those who live outside ectoparasites (lice). Parasitism is considered a special type of predation, where predator is smaller than prey, although in most cases does not cause the death of the host. When a parasite causes illness or death of the host, it is called pathogen.
Cymothoa exigua is a parasite that replaces the tongue of fish with their own body. Picture by Marcello Di Francesco.
Kleptoparasitism is stealing food that other species has caught, harvested or prepared. This is the case of some raptors, whose name literally means “thief.” See in this video a case of kleptoparasitism on an owl:
Kleptoparasitism can also occur between individuals of the same species.
One species has benefits and the other is not affected:
- Commensalism: one species (commensal) uses the remains of food from another species, which does not benefit or harm. This is the case of bearded vultures. It is also commensalism the use as transportation from one species over another (phoresy), as barnacles attached to the body of whales. The inquilinism is a type of commensalism in which a species lives in or on another. This would apply to the woodpeckers and squirrels that nest in trees or barnacles living above mussels. Finally, metabiosis is the use of the remains of a species for protection (like hermit crabs) or to use them as tools.
The woodpecker finch (Camarhynchus pallidus) uses cactus spines or small branches to remove invertebrates from the trees. Picture by Dusan Brinkhuizen. Both species have benefits:
- Mutualism: the two species cooperate or are benefited. This is the case of pollinating insects, which get nectar from the flower and the plant is pollinated. Clownfish and anemones would be another typical example, where clown fish gets protection and food scraps while keeps predators away and clean parasites of the sea anemonae. Mutualism can be optional (a species do not need each other to survive) or forced (the species can not live separately). This is the case of mycorrhizae, an association of fungi and roots of certain plants, lichens (mutualism of fungus and algae), leafcutter ants …
Atta and Acromyrmex ants (leafcutter ants) establish mutualism with a fungus (Leucocoprinus gongylophorus), in which they gather leaves to provide nutrients to the fungus, and they feed on it. It is an obligate mutualism. Photo taken from Ants kalytta.
INTRAESPECIFIC RELATIONSHIPS
They are those that occur between individuals of the same species. They are most beneficial or collaborative:
- Familiars: grouped individuals have some sort of relationship. Some examples of species we have discussed in the blog are elephants, some primates, many birds, cetaceans … In such relationships there are different types of families.
- Gregariousness: groups are usually of many unrelated individuals over a permanent period or seasonal time. The most typical examples would be the flocks of migratory birds, migration of the monarch butterfly, herds of large herbivores like wildebeest, shoal of fish …
Gregariousness of these zebras, along with their fur, allow them to confuse predators. Photo taken from Telegraph - Colonies: groups of individuals that have been reproduced asexually and share common structures. The best known case is coral, which is sometimes referred to as the world’s largest living being (Australian Great Barrier Reef), but is actually a colony of polyps (and its calcareous skeletons), not single individual.
- Society: they are individuals who live together in an organized and hierarchical manner, where there is a division of tasks and they are usually physically different from each other according to their function in society. Typical examples are social insects such as ants, bees, termites …
Intraspecific relations of competition are:
- Territoriality: confrontation or competition for access to the territory, light, females, food… can cause direct clashes, as in the case of deer, and/or develop other strategies, such as marking odor (cats, bears…), vocalization …
Tiger figthing for territory. Video caption by John Varty - Cannibalism: predation of one individual over another of the same species.
And you, as a human, have you ever thought how do you relate with individuals of your species and other species?
REFERENCES
- Zompopas
- Relacions de la biocenosi
- Ecología de las comunidades
- Els ecosistemes (xtec)
- National Geographic
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