The ecosystem
By Marjorie Henry, Contributor

Prime Minister Portia Simpson Miller greets Sean Douglas (left) and Serena Pettigrew, students of Haile Selassie High School track team, during a courtesy call at Jamaica House, recently. - Rudolph Brown/Chief Photographer

In the previous lesson, I shared with you information on one of the topics that has been included in the new Geography Syllabus that of the effect of relief on climate in the Caribbean. I hope you did the additional reading not only from the recommended texts but also from any other available source. How well did you do on the quiz to review the topic? Well check your answers now.

The aspects of climate that relief affects are temperature, rainfall and wind.

The rate at which temperature reduces with increase in altitude is 0.6ºC for every 100m.

Examples of mountainous Caribbean islands - Jamaica, Dominica. Examples of low-lying Caribbean islands are Antigua, Bahamas, Barbados.

The type of rainfall that results from the relief of the land is called RELIEF or OROGRAPHIC RAINFALL.

Relief rainfall - this involves a wind blowing against a mountain range, and the air having to rise over it. By rising, the air cools, condensation occurs and clouds are formed. Heavy rainfall usually occurs on the windward side of mountains (the side which faces the prevailing wind). The leeward side (the side which is sheltered from the wind) is usually very much drier, and is said to be in the rain shadow.

Strong winds occur on the windward side of the slopes.

Ecosystem is not exactly a new topic at this level of geography since formerly, topics such as soil and natural systems were studied. However, this is my focus in today's lesson as I continue to highlight aspects of the revised Geography Syllabus. You are required to know 'the components of an ecosystem - human. climate, vegetation, soil (living and non-living components)'. However, before looking at the components of an ecosystem, let us first offer a definition for it. Ecosystem is a contraction of 'ecology' and 'system'. In reference to the text Geography An Integrated Approach by David Waugh, we are told that the term ecology refers to the study of where organisms live. An organism's home or habitat lies in the biosphere, which is the surface zone of the earth and its adjacent atmosphere, in which all organic life exists. The scale of these homes varies. The ecological units are:

Microhabitat - small specific locations, for example, under a leaf or under a stone in a river;

Habitat - a more specific location with a particular set of conditions and an appropriately adapted community, for example, fresh water pond, hedgerows;

Zones - units within biomes, for example, three layers in the rainforest;

Biomes - large areas cutting across continents yet each with its own characteristic type of flora and fauna, for example, rain forest, desert.

Fundamental to these four ecological units listed above is the concept of environment. The environment is a collective term to include all the conditions in which an organism lives. Environment can be divided into two types as follows:

The physical, non-living or abiotic environment - this includes properties of temperature, water, light, humidity, wind, carbon dioxide, oxygen, pH, rocks and nutrients in the soil.

The living or biotic environment which refers to all organisms - plants, animals, bacteria and fungi.

The ecosystem is defined as a natural unit in which the life cycles of plants, animals and other organisms are linked to each other and to the non-living constituents of the environment to form a natural system.

Any change affecting any single element within the ecosystem must obviously have repercussions throughout the entire system. An ecosystem depends on two basic processes, namely, energy flow and material cycling.

Here is a quiz based on today's lesson.

1. Ecosystem is a contraction of what two words?

2. What term refers to 'the study of where organisms live'?

3. List the different ecological units in order of scale.

4. What is the meaning of 'environment'?

5. State the two divisions of environment.

6. Define ecosystem.

The topic continues in the next lesson as we look more specifically at the components of an ecosystem. May I encourage you to continue reading on the topic.

Marjorie Henry teaches at Glenmuir High School.