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8.9.1. Intraspecific and interspecific relationships

Intraspecific relationships

The intraspecific relationships are established interactions between individuals of the same species. These relationships can be harmful, if they provoke competition between individuals, or beneficial, if they favor their cooperation.
The competitive relationships occur when two or more individuals compete for:
  • The resources of the environment: food, light, etc.
  • Reproduction: trying to get a mate for reproduction.

Biological song: Headless Amantis. The song of the praying mantis.

  • Social dominance: an individual is imposed on the rest. For example, chickens have a social hierarchy in which some individuals dominate others.
The relationships of cooperation or association of individuals into groups allows to obtain benefits, such as protecting the young, facilitate reproduction, obtain food or defense. Some of these cooperative relationships are:

Family relationships

Groups are made up of parents and their descendants. Its main benefit is to facilitate the care of the young and facilitate reproduction. They may be:

  • Parental monogamous: Formed by a male and a female. For example, wolves or many birds.
  • Polygamous parents: Formed by a male and several females. For example, lions, buffaloes or zebras.
  • Matriarchal: The female is the one who leads the group, as in the case of elephants, whose females are in charge of three or four daughters, and their offspring. Males are solitary and go from one herd to another.

Gregarious relationships

Groups of individuals, not necessarily from the same family, who meet occasionally to search for food, defend themselves, reproduce or migrate. For example, herds of deer, schools of fish, or flocks of migrating birds.

Social or state relations

They are the hierarchical relationships that occur between individuals who could not live individually outside of that social life. Individuals usually present anatomical and physiological differences and have different functions, appearing various categories or castes. For example, ants, termites or bees.

For example, ants have a state relationship in which individuals are within a category (queen, worker, drone) performing a function (reproduction, feeding, defense), controlled by the queen.

Bees, in their hive, have a queen and hundreds of drones, while the rest are workers. The only function of the drones is to impregnate the queen. The worker bees are sterile females, and they are in charge of making the wax and collecting the nectar from the flowers.

Abeja reina

By HoraMora (Own work) [GFDL or CC BY-SA 4.0-3.0-2.5-2.0-1.0], via Wikimedia Commons

Colonial relations

The individuals remain physically united, inseparably, forming colonies. Descendants join their parents to form a common organism to survive, since individuals specialize in different functions (getting food, reproduction, defense, etc.). For example, corals.

Animation: Intraspecific relationships.

Interspecific relationships

The interspecific relationships are the interactions that are established between individuals of different species. They can be negative, neutral or positive relationships:

Interspecific relationships of competition

They are the relationships that are established between individuals of different species of the ecosystem that occupy the same ecological niche. They compete for the same food and occupy the same place in the food chain. They appear when the resource they share is limited, such as electricity, water, food, etc., and the species that is better adapted will be more efficient in the use of those resources and will displace the other.

Predation ratio

Relationship that is established when one species (predator) feeds on another (prey), which normally dies, to feed. The predator is usually larger than the prey and, in turn, can be prey to another predator. For example, the wolf and the lamb, the cat and the mouse, the big fish and the small fish, etc. Herbivores (sheep, giraffes, etc.) also prey on vegetables.

Humor and predation

Sometimes the predator seems to have trouble hunting its prey.

Parasitism ratio

It is a relationship in which one species benefits (parasite) by living at the expense of another that harms itself (host), from which it takes food and even accommodation. It causes damage but without actually killing it, since the survival of the parasite is linked to that of the host and it cannot live without it.

Two types of parasites are distinguished:

  • Ectoparasites: They live on the host's body: For example, lice, fleas, ticks, etc.

Video: Child with lice, lots of lice.

  • Endoparasites: They live inside the host. For example, tapeworms.

Ciclo de vida de la tenia

By EternamenteAprendiz (Own work) [CC BY-SA 3.0], via Wikimedia Commons

Mutualism relationship

In mutualism relationships, the two or more individuals associate temporarily, not permanently or obligatorily (individuals can survive without the help of the other), for mutual benefit. Some examples of mutualism are:

  • Cattle herons that feed on buffalo parasites.
  • Insects (bees, for example), and some birds (hummingbirds, for example), take advantage of the nectar of flowers and help pollinate the flowers, so both species benefit.
  • The honey-guide bird discovers a honeycomb, but since it cannot break it, it guides the honey badger, which breaks it to feed. Then, the bird feeds on the remains that have been left.

Text with video: Anemone and clown fish.

Video: Humans and honey bird.

Symbiosis relationship

The symbiosis is very similar to mutualism, since both species derive benefit, but differ in that it is a forced relationship. The two species cannot live independently and need each other to survive. Some examples of symbiotic relationships are:

  • Lichens. A lichen is formed by the symbiotic union between an alga and a fungus. The alga photosynthesizes and produces food. The fungus retains moisture and protects the algae from drying out.
  • Ruminants (cows, sheep, camels) have microorganisms in their stomach that help them digest the cellulose in the vegetables they eat. They both benefit.
  • Some bacteria (genus Rhizobium) live in the roots of leguminous plants and allow them to fix nitrogen to be able to synthesize proteins. Bacteria receive food.

Commensalism relationship

Relationship between two species in which one of them (commensal) benefits from the other but without harming it. Some examples of commensalism are:

  • The remora fish, which is located in the shark's ventral area. Thus, it is protected and feeds on the remains that escape from the shark's jaws. The shark neither benefits nor harms.

Video: Remora fish with shark.

  • Epiphytic plants, which grow on another plant that they use as a support but without feeding on it, such as orchids and some ferns.
  • Scavengers feed on the remains left by carnivorous animals.

Inquilism relationship

The inquilism is a relationship much like commensalism. A species (tenant) finds shelter in a structure of another organism that does not harm or benefit. Some examples are:

  • The hermit crab, which protects itself in the shell from another organism that has already died.
  • The "needle fish", which hides in holothurians (sea cucumber) when there is danger.

Cangrejo ermitañoBy Blue-banded_Hermit_Crab.jpg: Linda Tannerderivative work: Stemonitis (Blue-banded_Hermit_Crab.jpg) [CC BY 2.0], via Wikimedia Commons


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