Ecosystems

Ecologists invented the word ecosystem, an abbreviated form of ecological system, to describe a network consisting of organisms, their environment, and all of the interactions that exist at a particular place. The biosphere is a global ecosystem. Because it is too complex to study, ecologists limit their view to smaller regions, setting up more manageable boundaries. For the sake of simplicity an ecosystem may be a pond, a cornfield, a river, a field, a terrarium, or a small clearing in the forest.                                        Accordingly, ecosystems vary considerably in complexity, too. Some may be quite simple- for example, a rock with lichens growing on it. Others like the tropical rain forest, are quite complex. They contain an abundance of living organisms and a wide variety of species as well. A complete picture of ecosystems is not possible, though, until we look at ecosystem balance and imbalance to answer some important questions: How can ecosystems be altered, and in what ways can they recover from damage? Stability or balance doesn’t mean that all of the parts of an ecosystem operate in perfect harmony. Not at all. Ecosystem stability is often achieved through competition and apparent conflict: animals competing for a limited food supply, disease organisms killing off the weak, and predators feeding on prey. The net result, or the more or less constant condition, is what ecologists refer to as stability

An ecosystem consists of a number of living organisms and their physical environment. The living organisms and their non-living environment are interrelated and interact with each other.

There are six major components in an ecosystem:

1. inorganic substances;

2. organic compounds;

3. climate, temperature, wind, light and rain which affect all the processes in an ecosystem;

4. producers; green plants which are able to manufacture food from simple inorganic substance in the process  known photosynthesis;

5. consumers. Primary consumers: they obtain their ener­gy from green plants. But secondary consumers such as dogs and cats feed on other animals;

6. decomposers, such as bacteria and fungi. Bacteria break down the flesh of dead animals. Fungi break down plant ma­terial. They enable chemical substances to return to the phys­ical environment.

The main processes in ecosystems include: 1. food chains, 2. materials cycles, 3. development and 4. evolution.

Food Chains. The Sun's energy travels through an ecosystem. The proper transfer of energy through an ecosystem by the producers, the consumers and the decomposers is called a food chain.

Materials Cycles. Materials cycles include cycles of nitrogen, carbon, oxygen, water and mineral salts. Chemical substances move from the non-living environment to living things. They are then returned to the environment.

Development. An ecosystem exists in a state of equilibrium. It can support a certain number of plants and animals of differ­ent species. If the population of one animal increased, there would not be enough food and water for all the animals. Consequently, some would die. In this way the ecosystem reg­ulates itself and returns to its state of equilibrium.

Ecosystems are not static — they change all the time. Plants and animals are able to adapt to changes in the phys­ical environment. For example, if fire destroyed the vegeta­tion in a region, there would be certain changes. First grass and some flowers would grow. Then insects would appear. The wind would blow the seeds of small trees. These trees would grow and birds and animals would appear.

Evolution. During long periods of time ecosystems evolve. The evolution of an ecosystem is caused by factors inside and out­side it.

Consider the evolution of the atmosphere: when life began there was no oxygen in the atmosphere. Consequently the sun's rays prevented life from developing on land. The first living organisms developed under the sea. After the evolution of pho­tosynthesis, the oxygen in the atmosphere increased and life expanded. Complex living organisms developed. As the oxygen in the atmosphere increased, a layer of ozone was formed, life would be impossible without it on the surface of the Earth.

Today life on the Earth is in danger: man himself might destroy the equilibrium of ecosystem by pollution, extinction of wildlife and unreasonable utilization of the globe's material resource.