around the tree. If the aphids are not moved populations become locally so high that they suffocate.
But on Eco Island all life thrives: the Aphid Eaters are never hungry, the aphids never suffocate, the Ants are as happy as ants can be and the Eco Trees are healthy despite the aphids that live on them and despite spots of fungus on their leaves.
Thus an Ecosystem is the sum of nine conceptual components, listed below.
3.8.1 DEPENDENCY
The Aphids need the Eco Tree and the ants; the Eco Tree depends on the Aphid Eater birds to ensure that the Aphids do not become too populous, and it depends on the ants to give it the right soil conditions; the Ants need the Aphids for the honeydew. And there are many other less obvious and less direct dependency relationships. All living things depend on others to survive: to give them immediate sustenance and to create for them the right environment.
3.8.2 MUTUAL COEXISTENCE AND COMPETITION
The habitats of the ants, the aphids and the Aphid Eaters do not overlap: each has its own Niche. However, each individual competes with members of its own species for resources, for mates and for living room.
3.8.3 ENERGY FLOW
The Eco Tree gets is energy by photosynthesis (4.3.5); the aphids get their energy by sucking sap from the Eco Tree; and the Aphid Eater gets its energy by eating the aphids. Thus energy enters the Ecosystem from the sun and is lost only as heat generated by the activities of all the animals and during decomposition of detritus by the decomposers.
3.8.4 BIOMASS
Biomass is the total mass of life on Eco Island at any one time: it is both the result of productivity and an indicator, in terms of mass per unit area, of the productivity of the island.
3.8.5 PRODUCTIVITY
The Eco Tree is a Primary Producer, converting solar energy and inorganic material into living matter. The aphids, the ants and the Aphid Eater are Secondary Producers, depending upon the primary producer and each other to live. The productivity of Eco Island depends on its inorganic resources such as water and soil nutrients, while production itself is activated by energy.
3.8.6 RESOURCE CYCLES
Like the energy flow, the Eco Tree takes its nutrition from the soil, the aphids from the Eco Tree, and the Aphid Eater from the aphids. But, unlike the energy flow, this is a
