“You are what you eat… and you are what, what you eat, eats… and you’re even what, what, what you eat, eat, eats… and it repeats, it repeats, it repeats!!!”
(Charlie Mcgee – Formidable Vegetable Sound System)
In nature, organic systems are made up of living organisms that organise resources in the environment for their own means.
Every cell in every living thing, from the smallest bacteria to the largest tree, shares a fundamental requirement for the energy and matter to grow, function and reproduce.
Fortunately, the elements needed for life are to be found in most places on earth but organisms must be able to access the energy and materials they need in a form that is “biologically available”. As humans, we can go out and bathe in sunshine, but can’t directly access energy from it. Likewise, we’d struggle to get the calcium and other minerals needed to build bones by eating dirt.
However, there is a range of mechanisms that living species employ, individually and collectively, to ensure they can get hold of a suitable supply.
By in large, it all gets underway with a process carried out by specialized organisms called photoautotrophs. Plants, algae and blue-green bacteria alone can obtain energy from sunlight, to be used in the conversion of inorganic materials to organic ones. For the sake of simplicity, in this discussion, we are primarily going to focus on plants.
The source of just about all biologically available energy and the staring point of organic matter is the carbohydrate molecule formed during photosynthesis
Carbon Dioxide + Water + Sunlight = Carbohydrates + Oxygen
Chlorophyll, found in the cells of vegetative species is the factory where organic chemistry begins. This is the original source of both the fuel that drives the majority of life activity, and the initial molecules from which, along with other elements, organic materials are built.
With available energy, and carbohydrate molecules in place, the other nutrient elements that are integral to the assembly of living materials can be acquired from the environment.
A source of nitrogen is essential as it is the basis of proteins and a major component of genetic material and chlorophyll. Approximately 78% of the air is nitrogen but only nitrogen-fixing bacteria have the faculty to make this nitrogen biologically available. Quite a bit of energy is required to do so, but plants readily offer up some of their calorie rich carbohydrates and even accommodate these bacterial allies, in exchange for a regular nitrogen supply.
Once nitrogen enters the scene, the assembly of amino acids, enzymes, hormones and all sorts of compounds, involving small amounts of mineral nutrients, is set in motion.
Plants can take in mineral nutrients such as calcium, magnesium, phosphorous etc… through their roots, along with water, but their ability to access and acquire the required minerals from the soil matrix is somewhat limited. Soil dwelling organisms like mycorrhizal fungi and mineral solubilising bacteria are far superior in this department. Again, plants allocate a portion of their quota, in the form of sugary root exudates, to these microbial networks as down payment for delivery of organic nutrient packages.
These transactions, involving the direct provision of carbohydrates, by living plants to microbial associates, for the acquisition of other nutrients that are integral to the make up of organic materials, is the means by which biomass is most effectively produced.
At this point, the inherent material elements and energy of life are biologically available on the open market. From here on in, species essentially consume energy that has already been produced and materials that have already been acquired. In the consumption and metabolism of organic resources, energy is burnt or dissipates and materials are recycled or lost back to the environment, beyond which more energy and material elements are needed to keep the wheel turning.
The evolution of organisms that eat living plants may seem like a counter intuitive biological strategy but in some circumstances, this can improve overall production. For instance, pests and diseases will often target weaker plants, effectively making way for better prospects. The rate of photosynthesis can also drop off when plants enter phases of reproduction, or as they approach full maturity. Vegetative growth of herbs and grasses in particular can be stimulated and prolonged by a graze from passing herbivores. As they go, animals excrete nutrient rich by-products of the digestion process, depositing fertility through the landscape.
Successive populations of microorganisms also consume one another, passing materials on at various stages along the way. We now know that even plants consume microbes by extracting the cellular contents of bacteria that are enticed into the cells of plant root tips.
In this way, consumers turn over materials in living organisms that are under-utilised so they can be used more effectively.
At the end of the line, what’s left of what once lived still has energetic and material value, as witnessed in the heat, smoke and ashes generated by burning dead matter. Decomposers including saprophytic fungi, small invertebrates, worms, protozoa, bacteria, yeasts etc… get by largely on deceased organisms. In combination, they break down residual materials, using up much of the remaining energy. Nutrients liberated in the process are available once again for plant uptake.
Decomposers recycle and repurpose used materials that would otherwise be wasted or lost.
Up to this point, we have been discussing the interactions involving energetic and material goods in biological systems but there are also many vital cultural services that organisms have developed, which are viable terms of trade in their own right. Examples of these are too numerous to list, but a few are well worth mentioning.
For starters, many plants recruit other organisms for assistance with reproduction and distribution. Flowering plants use a range of strategies to entice insects, birds and mammals into helping with pollination. As animals move around and access food, often, they also inadvertently spread propagation material to new ground.
There are microorganisms that defend plants from attack, and others known to manufacture beneficial compounds that promote growth, induce immunity or improve resilience to environmental stress. Larger predators like carnivores offer protection too, by regulating herbivore activity. In the grasslands and meadows of the world, they not only keep grazing populations in check, but also induce the behaviour whereby these herds bunch up and continually move on to fresh forage, allowing plants in their wake, time to recover.
Of major significance, is the way different species modify their living environment, vastly improving growing conditions. In the soil, finer particles get coated with the humus end products of organic material decomposition, and stick together to form micro aggregates . Micro aggregates are continually bound, by the actions of mycorrhizal fungi, plant roots and soil organisms like earthworms, into relatively stable macro aggregates. Water and nutrients are better retained within the contained environment of soil aggregates through fluctuating seasonal conditions. The gaps between aggregates enable water, air and for that matter, plant roots, to move down into the soil, and gases released through decomposition to escape up and out. There are more stomata pores on the underside of leaves for good reason! Other larger soil microbes and animals also create channels for air and water as they move up, down and around the soil; as do decaying roots. Unlike dirt, there is structure in living soils, making materials far less prone to being washed or blown away. On a global scale, the sequestration of carbon and the release of oxygen, from photosynthesis, have altered the composition of earths’ atmosphere over time, cooling the planet. So too, is heat released from the water vapour of transpiring plants, when it precipitates in the upper atmosphere. This is a much better scenario than the reflection of radiation that occurs when solar energy hits bare soil, part of which is trapped by greenhouse gases. Finally, hydrophilic bacteria that float up to the atmosphere from the plant canopy cause something called bio precipitation. By inducing condensation and the formation of raindrops, they clear the atmosphere of vapour and hazes that trap heat, and return water to the earth, enabling further plant growth and transpiration, and so it goes.
Over billions of years, intricate self-serving dynamics have co-evolved between participants within diverse living communities, that one way or another, all play their part in an organic economy where the interests of the individual align with that of the whole.
It begs the question, where do humans fit into all this ?