Symbiosis, Living together

By januari 21, 2022 Algemeen


Life on Earth is complex and interactive, with organisms forming populations, which in turn form communities, or ecosystems, both locally and globally. The ecology is defined by the interactions between species and their composition within that system that drives natural selection, evolution, and genetic composition. The fitness for survival of an organism in any ecosystem is not dependent solely upon the species but includes the interactions of other organisms with that species. Symbiosis, the nature of the interactions between different organisms living in close physical association, is omnipresent and played an essential role in the evolution of many current forms and refers to close and often long-term interactions between organisms of different species.

In ecosystems all over the world, there are immense, mutually beneficial associations of macrofungi with flowering plants in complex, positive, metabolic, symbiotic relationship to each other. Interactions between and among species within an ecosystem can be simple or complex, competitive or beneficial, predatory or symbiotic. The more we learn about nature, the more symbiosis seems ubiquitous. The most dramatic examples of symbiosis as a factor in evolution are those cases of endosymbiosis wherein prokaryotic organisms have become regular ‘inhabitants’ of eukaryotic cells, with the now well-established case of mitochondria and chloroplasts having descended from prokaryotes being the major examples.

It is of great importance to understand how ecosystem parameters can be guided by key ecological players in the system to maximize benefits for the life-chances of whole species. For example, health in forest ecosystems is regulated by what are called ‘mother trees’ that control fungal networks that in turn interconnect trees of varying ages. The control system works to regulate nutrient flows to trees that need them most, such as very young ones. It also works to transfer information and energy from dying species to those that might continue to thrive, thus maintaining the forest as a larger system. Given that forest ecosystems are foundational for most life on earth, including humans, the so-called wood-wide-web is a prime example of natural justice and the attempt to maintain balance or total homeostasis in nature.  This insight can now be re-asserted as crucial for all aspects of human enterprise and can be traced to the earliest beginnings of evolution. These crucially important insights have yet to be incorporated into ecological thinking applied to politics and human societies.

Most symbiotic relationships probably started out as facultative. Over many generations, the organisms came to depend more on the symbiosis because natural selection favored those traits and not others. Eventually, the symbiosis became the sole source of the food, shelter, enzyme, or whatever else the symbionts derived from one another. Since symbiosis was identified as a potential for evolutionary innovation, the conditions that favor it and its subsequent evolutionary outcomes is looks that virtually all species on Earth are involved in multiple interspecific interactions at anyone time.

Most relationships between plants and animals are viewed as unidirectional, as in the model of a food chain where an herbivore eats plants and carnivores eat herbivores. As aforementioned, many relationships between organisms are more complex and involve multidirectional interactions. Symbiosis commonly describes close and mostly long-term interactions between different biological species. One organism has evolved to use the other as a unique habitat or niche that it can exploit to gain a competitive advantage. There are three general types of symbiosis: mutualism, commensalism, and parasitism. Based on the nature of the interaction between organisms, symbiotic relationships are loosely grouped into one of these types. The changes in circumstance that bring about shifts in the nature of a symbiosis can also have a temporal element. Over different timescales, a lineage of symbiont may make the transition from parasitism to mutualism, and then back again to parasitism. In symbiosis, at least one member of the pair benefits from the relationship. The other member may be injured, i.e., have the parasitism association, or be relatively unaffected, i.e., have the commensalism association -commensalism is loosely defined as a symbiotic relationship in which one organism benefits and the other is unaffected-. An other type of relationship is mutualism; in this type both the partners get benefit from the associationship. Endosymbiosis is any symbiotic relationship in which the symbionts (cohabiting partners)  live within the tissues of the host, either in the intracellular space or extracellularly. Ectosymbiosis, also referred to as exosymbiosis, is any symbiotic relationship in which the symbiont lives on the body surface of the host, including the inner surface of the digestive tract or the ducts of exocrine glands.

Plants are the very foundations of life on the earth. A large proportion of the microbial population are present in the region immediately around plant roots, the rhizosphere. The surface and immediate neighborhood of a root provides a specialized environment for microorganisms where the microbial population is enhanced because of the root exudates. Almost 90% of all vascular plant families enjoy symbiotic relationships with microorganisms. Most symbiotic relationships probably started out as facultative. Over many generations, the organisms came to depend more on the symbiosis because natural selection favored those traits and not others. Eventually, the symbiosis became the sole source of the food, shelter, enzyme, or whatever else the symbionts derived from one another. Symbiotic relationships in which both the species of the association benefits are mutualistic. Mutualistic relations between plants and fungi are very common. The fungus helps the host plant absorb inorganic nitrogen and phosphorus from the soil. Some mycorrhizal fungi also secrete antibiotics which may help protect their host from invasion by parasitic fungi and bacteria. One of the most important examples of mutualism in the overall economy of the biosphere is the symbiotic relationship between certain nitrogen-fixing bacteria and their legume hosts. Leguminous plants (family Fabaceae (or Leguminosae), or the fruit or seed: beans, soybeans, peas, chickpeas, peanuts, lentils, lupins, mesquite, carob, tamarind, alfalfa, and clover) form a symbiosis with rhizobial bacteria (established inside the root nodules of legumes) and fix large amounts of elementary nitrogen (N2), an extremely important process for nitrogen availability in many terrestrial ecosystems.

Corals are the product of a symbiosis between cnidarians (corals, sea fans, sea whips (colonial species)) and green algae, allowing the building of entire reefs.  Each individual provides an advantage to the other, enabling them to exploit each other and thereby enhance their chances of survival. An example is the anemone-clownfish mutualism, in which the clownfish gets food scraps from the anemone and uses the stinging cells of the anemone for protection. The anemone gets smothering algal cover cleaned off by the clownfish and absorbs nutrients from the clownfish’s nitrogenous waste, so both organisms benefit. Another well-known example of mutualism is the relationship between corals and zooxanthellae, a type of algae that live in corals. The coral gets extra nutrition from the algae as it photosynthesizes, and the zooxanthellae are protected by the hard coral and obtain plant nutrients from the coral (e.g., ammonia).

No doubt, conflict between organisms exists, but an overall balance of interests (eco-homeostasis) is in the total interest of all life. In addition, ecology itself is a radical concept in that it requires of us all to live within the limits of nature and to live with all the other life forms that share this Earth.

The new era will be characterized by human intelligence that replicates the symbiotic and mutually reinforcing life-reproducing forms and processes found in living systems. Given that we have evolved as a species within the pre-existing evolutionary matrix, such intelligence lies within us as latent potential. The elements include full recyclability of all inputs and outputs, the elimination of toxic waste in all aspects of human enterprise, safe and socially just renewable energy, and full and harmonious integration of human industry and technology with physical and living systems at all scales.

Human action, culture, and enterprise will be exemplified by those cumulative types of relationships and attributes nurtured by humans that enhance mutual interdependence and mutual benefit for all living beings (which is desirable), all species (essential), and the health of all ecosystems (mandatory). Human development will consist of creative actions that use the very best of biomimicry together with other eco-industrial, eco-technological, eco-agricultural, and eco-cultural innovations.

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