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The Pyramid of Producers and Consumers⁵

The green plants are the primary producers in the ecosystem, for they capture the sun's energy in high-energy biomolecules which they and the consumers in the system can use. The consumers may be classified as herbivores (which eat plant materials), carnivores (which eat herbivores and carnivores), supercarnivores (which eat other carnivores), and the decomposers (bacteria, fungi). At each consumer stage, about ninety percent of the food energy is either not assimilated or is used for life processes rather than being stored. Because of this inefficiency each population annually consumes food equivalent to many times its own weight.

Since plants provide food for many insects and animals, a very large number and mass of plants is necessary. The energy stored in each level of consumers is reduced to roughly one-tenth that stored by the members of the preceding level below. This is illustrated in the diagram of the ecological energy pyramid (a pyramid of biomass would be similar in shape, for the stored energy is proportional to the dry weight or mass of the plant or animal material). Note that the primary producers, the plants, generally form the large base, whereas each of the successive levels of consumers is increasingly smaller in stored energy and biomass.

figure 4-2. Pyramid of biomass in grasslands. The base is the great mass of grass, shrubs, and trees. Next come the herbivores such as antelope, zebra, and wildebeest, and finally the carnivores such as lions, hyenas, and wild dogs. The decrease in total mass of living things at each successive consumer level is required by the inefficiency with which a consumer stores the energy contained in the food consumed.

For the first example of such an ecosystem pyramid, consider the African veldt where large quantities of grass and shrubs grow. Great herds of many different kinds of herbivores--antelope, buffalo, wildebeest--roam the plains, feeding on specific kinds of vegetation. The carnivores include lions, hyenas, wild dogs. There are also scavengers such as jackals and vultures, and finally the carrion-consuming insects and the decomposers in the soil.

The ocean presents excellent examples of communities of living things. Here the primary producers are the phytoplankton, microscopic single-cell plants in the surface water layers which absorb sunlight and produce the basic food supply for the entire community. The microscopic zooplankton are tiny animals which feed on the phytoplankton. Small fish, tiny crustaceans and other invertebrates feed on the plankton. Larger fish feed on the smaller, and so the food chain extends to the supercarnivores such as sharks and swordfish.

The actual complex of food chains in any ecosystem is much more complicated than the brief sketches given above, but the principles of interdependence, energy flow, material cycles, and the pyramid relationships are, with variations, common to them all. When the complexity and balance of the biosphere and the beautifully adapted and unique environmental conditions on the earth's surface are considered, one is impressed with the reality of an intelligent master plan in nature.

The Creator designed nature so that no single plant or animal could produce too many of its own kind. If too many of one species survive, the balance of nature is upset. For example, excessive numbers of porcupines can damage a forest, and they will multiply beyond the sustainable limit if suitable predators are scarce. In northern forests the most successful predator of porcupines is the fisher. This animal has been hunted almost to extinction in some areas, with resulting damage to the forests. Now the fisher is being protected and the porcupine populations are coming under control. Thus a dynamic balance of nature preserves the natural order for the benefit, that it, the preservation of all the species. Especially benefited is man whom God has set to be His steward over all the other creatures on the earth.

Many interesting interrelationships exist between different kinds of animals, kinds of plants, or between plants and animals. Sometimes one organism cannot survive or even reproduce without another as part of its environment. Many illustrations of this are to be found among the pollen-bearing plants and the pollenating insects, where special design characteristics make a particular insect necessary or specific for a particular plant, and sometimes also the plant necessary for the insect. In all of these sometimes amazing details and in the balance of nature, according to the creation point of view, one sees evidence of wisdom, intelligence, purpose, plan.

References

5. Curtis, Helena, (ref. 1), 438-456.