In the previous lesson of ECONATICS, we have looked at the importance of the non-living components of the ecosystem. In this lesson we will concentrate on describing the living or biotic components of the environment (Supporting article R). The concept “biotic” actually refers to all material that consists of carbon. It therefore also includes organisms that have deceased. We know by now that the health of living things relate directly to the condition of a-biotic components (such as water and air) at their disposal. But there also exists very strong interdependent links between biotic elements among each other.
There exists tremendous diversity in the interconnected chain of life on our planet (Supporting article K). Many forms of animals and plants have probably not yet even been discovered and many have become extinct even before they became known to us through fossilized material. The well-known paleontologist (some one who studies fossil plants and animals) Stephen Jay Gould estimated that 99% of all plant and animal species that have ever existed have already become extinct, and most of them have left us no fossil records. It is also interesting to realize that humans and other large animals are very, very rare life forms, as 99% of all known animal species are smaller than bumble bees.
There exist a number of ways by which animals and plants could be classified. We will first look at two generally used methods and thirdly at a method used by ecologists that emphasizes the relationships between different organisms as well as their relationship to their habitat.
1. TAXONOMIC APPROACH TO THE CLASSFICATION OF BIOTA
We love the beauty of animals – vertebrates and invertebrates (Supporting article O) and plants, but to see the structure and functioning of vital Micro and Macro organisms (Supporting article N) could sometimes be even more fascinating. Have a look at Supporting articles G, and F to get a better understanding of this fascinating world of organisms. Remember that micro and macro organisms outnumber by far the kingdoms of plants and animals that we are used to. Often we see the public media emphasizing the protection of endangered wildlife such as rhino’s and tigers (the so-called “big and hairy”), small micro and macro creatures might even be more vital for the survival of life on earth.
Firstly scientists use a ranking system, or taxonomy (Supporting article M) to orderly arrange and connect living things (or what they refer to as life) according to some scheme of resemblance. The basic classes are traditionally referred to as “Kingdoms”. Over the years the number of kingdoms in generally accepted classifications has grown from:
· Two kingdoms - animals and plants, to
· Three kingdoms - animals and plants and protista – microscopic single-celled organisms, to
· Four kingdoms - where distinction is made between microscopic organisms (protista) whose cells do have a distinct nucleus - eukaryotes – (kingdoms protista, plantae and animalia), and those who do not have a distinct nucleus - prokaryotes – (kingdom monera)),
When they realized the importance of the distinction made between eukaryotes and prokaryotes, the taxonomic rank order was altered. Empire Prokaryota (with kindom Monera sorting under it) was distinguished from Empire Eukaryota (with kingdoms protista, plantae and animalia.
· Five kingdoms - when animal traits were observed in fungi (multi-cellular saprotrophs) it had to be distinguished from multi-cellular autotroph plantae, and so a fifth kingdom was established).
· Six kingdoms - later some scientists felt that distinctions of kingdoms should be based on genetic characteristics. They found that, based on their genetic structures, not all organisms (from both the Prokaryota and Eukaryota Kingdoms
When one deals with the classification of living things, the starting point of your reasoning will largely determine how various forms of life may appear to relate to one another. Over the ages many individuals contributed to this process (Supporting article T). What Carolus Linnaeus, Jean Baptiste de Lamarck and Charles Darwin popularized during their times (Supporting article U) was the result of thousands of year’s speculation, and I daresay that their views might still again be re-written as new species are being discovered.
To conclude, in general the "classic" six-kingdom system consists of: Animals; Plants (that has been split into Plantae and Fungi); and single-celled organisms have been split into Bacteria, Archaea and Protista. But since about 2000, some research no longer support any of the traditional systems. In the following web page there is a rather lengthy explanation of the various categories and methods of arranging life into distinguishable groups: http://en.wikipedia.org/wiki/Kingdom_(biology).
2. FUNCTIONAL APPROACH TO CLASSIFICATION
Secondly, one can differentiate between organisms in an ecosystem by looking at the function they fulfill in the food network (Supporting article Q). A food network or food web is an interconnecting network of food chains. In a food chain energy is transferred from green plants through a sequence of organisms in which the one organism eats the organism below it in the chain and is eaten by the one above.
We can divide biotic components according to their main role namely, producers, consumers or decomposers. The producers in an ecosystem are those organisms which are able to manufacture organic compounds from inorganic substances. Inorganic elements such as calcium, iron, etc. are being taken up by the roots of plants and synthesized into organic compounds (such as starches, protein, etc.).These green plants (or vegetation) also absorb energy from the sun and through the process of photosynthesis make the organic compounds available to consumers. Green plants are therefore independent of other organisms to function while consumers are heterotrophic as they rely on autotrophic organisms for their energy needs.
The role of plants is extensive. Apart from their fundamental role in transforming the sun’s energy (by means of photosynthesis) into food (chemical energy) for herbivores, plants influence the formation of organic content in soil as well as the recycling of nutrients. Roots of trees transport nutrients from deep under the surface and eventually returns it to the surface (in the form of leaves, wood etc.) that fall to the ground where it rots (decompose) and is returned to the soil in the form of nutrients to the upper layers of the soil – available to shallower root systems of shrubs, grasses, etc. Furthermore plants cool the surface as they provide shade. This further enhances the performance of micro-organisms that break down organic matter. Plant roots bind soil together and prevent erosion caused by floodwater and together with the canopy (leaves, grass cover) it minimizes the erosive effect of heavy rains on the soil surface.
Consumers are dependant on producers for their energy needs. They can further be subdivided into primary consumers or herbivores (plant-eaters), secondary consumers or carnivores (meat-eaters) and omnivores (both primary and secondary consumers). Omnivores like humans can even be tertiary producers when they process their food into products like cheese from milk. Those carnivores that kill their prey and eat it are called predators and those who eat what is left by the carnivores are called scavengers.
The third group into which biotic elements can be divided is called decomposers. Among decomposers we get Macro-decomposers which include for example earthworms and wood lice. The Micro-decomposers consist of a large variety of bacteria, fungi and other single-cell micro-organisms. Decomposers live on dead organic material and therefore obtain their energy by consuming corpses of animals and dead plant material. They break down all the organic material (compounds such as proteins) of the bodies of producers and consumers into inorganic materials (elements such as magnesium) that are restored to the soil or water. These elements (or minerals) could then be taken up by the roots of plants (producers) from where it is transformed again into compounds through the processes associated with photosynthesis.
We have already explained how all components (biotic and a-biotic) are bound together in a dynamic functioning system by means of energy flow. So before we move on, we need to refer to food pyramids and the transfer of energy in the food network (Supporting article L). When a herbivore (e.g. rabbit, cow, giraffe) eats, only a fraction of the energy that it gets from the green plant becomes new body mass; the rest of the energy is used up by the herbivore to carry out its life processes such as movement, digestion and reproduction or is lost as waste. Therefore, when the herbivore is eaten by a carnivore (e.g. lions, leopard, fish eagle), the herbivore passes only a small amount (not more than 10%) of the total energy that it has received from green plants to the carnivore. Of the energy transferred from the herbivore to the carnivore, some energy will be "wasted" or "used up" by the carnivore. The carnivore therefore has to eat many herbivores to get enough energy to grow. For a schematic presentation of this process, you can refer to: Hugo,M.L. 2004. Environmental Management: An ecological Guide to Sustainable Living in Southern Africa . Par 3.4) www.environmental-management.co.za.
Because of the large amount of energy that is lost at each link, the amount of energy that is transferred gets smaller and smaller. Therefore the further along the food chain you go, the less food (and hence energy) remains available. When there are too many links in a single food chain the animals at the end of the chain would not get enough food (and hence energy) to stay alive. Most food chains have no more than four or five links. Therefore many animals are part of more than one food chain and eat more than one kind of food in order to meet their food and energy requirements. These interconnected food chains form a food web. Energy flow in food chains could be graphically represented in food pyramids, but more on that in our next lesson, called ‘Dynamics in the Ecosystem’.
From the perspective of human survival on earth, the concept of loss of energy along the food chain, tells us that the shorter the food chain, from which humans eat, the more likely they are to be able to provide enough for the growing population. In simplistic terms: if we eat only plant material (such as wheat) the earth can support more people than if we depend on meat. This lies at the core of human survival on earth.
3. CLASSIFICATION BY LEVELS OF ECOLOGICAL ENGAGEMENT
Supporting the holistic approach we have with ECONATICS, we are however not only concerned with the categorizing and eating habits of biotic components but rather the inter-relationships between different organisms and their habitat. This is the field of expertise that ecologists involve them with and which leads us to the third categorizing method in our discussion by which biotic elements could be grouped.
For their purpose ecologists classify the terrain of ecological research under five categories or levels of engagement (Supporting article P). We will start with the smallest and end with the category most inclusive of all life on earth.
Individual organisms: These are single individual animal, plant or life forms (species). Their main objectives here are to survive and reproduce.
Populations: These are groups of individual organisms belonging to the same species living in the same area.
Communities: This applies to a situation where individuals from various species co-exist in the same habitat. Individuals from the same species only compete with one another for the same resources, for example a herd of giraffe competing for leaves high up in trees. Members of another species, for example zebra feeding on grass can co-exist with the giraffe competing amongst one another for food.
Ecosystems: These are different communities consisting of various species of any scale interacting together and with their physical-biological environment. Ecosystems encompass the interactions of various communities within a certain environment.
Ecosphere: This is the part of earth where active life is possible, namely the zone that includes the atmosphere, sea and surface water and soil. All ecosystems together form the ecosphere (Supporting article S).
“It is not always possible to make sensible divisions between these levels, as all species exhibit mutually interwoven characteristics that make it impossible to study any aspect of ecosystem organization in isolation. An analytical study on different levels is nevertheless necessary in order to obtain a clear picture of the whole ecosystem.” (Hugo,M.L. 2004. Environmental Management: An ecological Guide to Sustainable Living in Southern Africa . p60)
In terms of their biological or biotic role, one would categorize humans along with other omnivores as consumers. However the impact that human consumption has had on the natural environment can not be compared to the effects animals have (Supporting article H). Related to most other consumers in the ecosystem, humans exert such a major influence on its environment that the very existence of life on earth seems to hinge around human activity. Human population growth has led to remarkable industrialization (causing the burning of fossil fuels and with it the increase in CO2 levels, the greenhouse effect and other forms of pollution); deforestation (causing loss of natural habitats and biodiversity as well as loss of oxygen producers and CO2 eliminators, namely trees); the manufacturing of harmful substances (herbicides and pesticides and DDT); ozone depletion and global warming. Even in Kenya
Humans have the ability to encourage the establishment and maintenance of biotic elements in ecosystems or to destroy ecosystems almost in the blink of an eye (Supporting article A). Humans are able to peacefully coexist with their pets and there are groups that encourage this healthy coexistence (http://www.vetsol.co.za/education.html). However, most forms of development to favor humankind at this stage are having negative consequences on the natural systems of the world. We need to seriously invest our time and energy to adapt our way of life towards harmonious co-existence with the various elements of nature (Supporting article B and E).
It is important to know that what we are talking about is not simply an emotional or theoretical New Age-driven concept of a few extremists. For too long have people acted with apathy and even contempt towards this message because it did not affect their daily lives directly; nor their pockets. The results of global warming (regular floods in Australia and South Africa , fires in Russia , extreme cold in America
