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Cycles, Balance, and Life

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For hundreds of millions of years, the chemicals and elements found on Earth have remained relatively constant, or in other words, they have changed very little. The amount of one element or chemical in the Earth’s surface is practically the same as it was many millions of years ago. This consistency is one of the things that makes life on Earth possible.

This balance is maintained via complex interactions or cycles between the Earth and its organisms, or lifeforms. The elements of the Earth are taken into lifeforms, used to sustain the organism, and later released in the form of waste, or through decomposition upon the death of the organism.

Most of these cycles only take a few months or a few years to complete. However, some can take many millions of years.

The Energy Cycle

Each day as the Sun rises, our little blue world is showered with heat and light. This energy from the Sun is very important to all life on Earth. Without it, life could not exist.

While most of the heat and light that reaches the Earth is either reflected or radiated back into space, some of it is captured by plant life through the process of photosynthesis.

Photosynthesis takes place when plants use sunlight in order to produce sugars. These sugars can then be used by the plant as food in order to sustain the functions of life.

Animals and humans do not have the ability to produce their own food. Thus, they must obtain their energy by eating plants, or by eating other animals that have eaten plants.

At some point as plants or animals die, or release waste into the environment, the heat from the Sun is released back into the environment.

Food Chains

In previous sections we have studied how the many different substances needed for life are passed from the Earth to lifeforms, and then from one lifeform on to another, until these substances are eventually returned to the Earth.

These many different cycles are primarily carried out as one organism consumes, or eats, another in a complex chain known as the food chain.

The most important part of any food chain are the plants that take the energy from the Sun and substances from the atmosphere and soil to produce food.

As one organism eats another, it uses a portion of these substances to sustain itself, and discards the rest in the form of waste.

Ecosystems

The plants and animals that are found in a particular location are referred to as an ecosystem. These plants and animals depend on each other to survive. In a delicate balance, these lifeforms help to sustain one another in regular patterns. Disruptions to an ecosystem can be disastrous to all organisms within the ecosystem.

As an example, consider what happens when a new plant or animal is introduced into an ecosystem where it did not before exist. The new organism competes with the natural organisms from that location for available resources. These unnatural strangers can push other organisms out, causing them to become extinct. This can then affect still other organisms that depended on the extinct organism as a source of food.

Throughout the history of the Earth, the delicate balance found within ecosystems has been disrupted by natural disasters such as fires, floods, storms, volcano eruptions, and so forth. In recent years, however, mankind has increasingly been affecting the many ecosystems around the world.