Earth Science: Biology – Ecology – Types of Cohabitation
A particular form of cohabitation between different species, advantageous for both partners, is symbiosis (also referred to as mutualism).
This is in contrast to other parasitic relationships where organisms feed partially or completely at the expense of others, while they live temporarily or permanently on or inside their body.
Earth Science: Biology – Ecology – Mutual benefit
In symbiosis, species that are different but adapted to each other live together. Here, one distinguishes between spatial relationships (endo- andectosymbiosis) or according to the degree of the reciprocal dependency.
Endosymbiosis is a symbiotic relation- ship where one of the partners (symbionts) lives in the body of the other. An example of such a close relationship is found among lichen, where fungi live in association with green algae or cyanobacteria. The shape and structure of the lichen aggregation is created by fungi (mycobiont); the algae or bacteria (photobionts) are usually located in the upper part of the thallus (vegetative body), so that they obtain sufficient sunlight for photosynthesis.
The advantage for the photobiont is, among others, protection against desiccation. On the other hand, the mycobionts receive a large part of their required nutrients from their active (photo- synthesizing) partners. Consequently, lichen can grow even in extreme locations. This relationship, where both partners are completely dependent on each other, is called mutualism.
In ectosymbiosis, the symbionts do not live inside the body of their partner. An example of this is the symbiosis of clown fish and sea anemones. The latter protect the fish with their stinging tentacles and, at the same time, profit from food remnants generated by clown fish feeding among their tentacles. Moreover, the fish often defend their symbiotic partner against predators. Frequently, symbiotic organisms are subdivided based on the type of their dependency.
Commensalism, for example, occurs when only one partner derives benefit from the association. This is the case when, for instance, animals benefit from the protection of a partner, without damaging or being of use to that partner. The burrows of large marine worms or shellfish very often contain “uninvited guests,” not only for protection but also because they utilize food remnants or waste products.
Protocooperation occurs when two organisms enter into only loose relationships, which could benefit both, but are not imperative because the participants are also able to live alone. An example of this is the already mentioned partnership between clown fish and sea anemones.
MYCORRHIZA
Mycorrhiza is an important type of co-habitation between the roots of higher plants and fungi.
There is a difference between endotrophic mycorrhiza, where fungal hyphae penetrate the root cells, and ectotrophic mycorrhiza, where the roots are enclosed by an envelope of fungal hyphae that penetrate only into the interspaces between cells (extracellular) of root bark.
TYPES OF COHABITATION
A particular form of cohabitation between different species, advantageous for both partners, is symbiosis (also referred to as mutualism).
This is in contrast to other parasitic relationships where organisms feed partially or completely at the expense of others, while they live temporarily or permanently on or inside their body.