In this week's article I highlight some of the different branches of ecology, just to give you an idea of how many areas are influenced by ecology. Basically there are five types or branches of ecology; organismal, population, community, ecosystem and global, all of which will be briefly described in this article.

But before diving into the different types of ecology, I would like to start off by defining ecology, which is the study of how organisms interact with their environment.

The first branch of ecology I will look at is organismal ecology, which includes physiological and behavioural ecology or organisms.

This branch of ecology looks at how organisms respond to the living (biotic) and non-living (abiotic) components in their environment. Therefore it addresses their behaviour, physiology and morphology with respect to how its structure relates to its function. Some animals look "funny", for instance, the male of some moth species have very feathery antennae which at close range makes them look like they are wearing the elaborate head-dress of a masquerader on Carnival day. But these tiny feathery projections are necessary as they increase the surface area of the antennae so that the male moths can sense the pheromones of the females and locate her for mating.

The next branch of ecology is population ecology, which generally looks at the three phases of the life cycle of a population; growth, stability and decline. But before going further let's first define what a population is. A population is simply a group of organisms of the same species living in the same place at the same time.

With respect to the life stages of a population, growth occurs when the available resources exceed the number of individuals present, so that the population can expand and there are enough resources to feed new members. Usually in this phase the reproduction rate is fast and there is a low death rate. However, resources are limited so there are only a certain number of individuals in the population that can be maintained, so that at this point the population reaches the next stage - stability.

the number of individuals in the population decreases and the population may eventually go extinct. The reasons for this are many, such as, environmental factors, increase in predators, illness, low genetic diversity so that members are susceptible to diseases, over hunting and pollution by humans.

Then there is community ecology. In its simplest terms, a community can be defined as a collection of organisms in a specific place and/or time. This simple definition means that in this branch of ecology, one compares how the community structure differs between places or regions, or if in the same place at different times. The latter of which is important when looking at whether there is loss in biodiversity.

In this branch of ecology, research is focused on the interactions between the organisms in the community and how they affect the community structure. Some types of interactions examined in community ecology include, mutualism, where in this type of relationship, both organisms benefit. Another type of relationship is predation, where one organism benefits while the other is either damaged or killed. Parasitism is another form of predation but instead of feeding on the carcass of the prey organisms, the parasite eats its prey or host while it is still alive. It should also be noted that herbivores are also considered predators.

But why study these interactions? Well take predation for example, the study of this interaction between organisms is important as it affects population size and species composition and in turn biodiversity of a community. Another important interaction is competition.

What has to be kept in mind is that resources are limited, for example, sunlight, food, water, shelter and mates. So in order to obtain enough resources to survive, organisms in a community must compete with one another.

The next branch of ecology is ecosystem ecology which takes community ecology a step further by looking at how organisms in a community interact with the non-living components, like soil, nutrient, rainfall and temperature.

Focus in this area is often placed on the cycling of nutrients and the flow of energy. In this branch, focus is also placed on ecosystem services, like water purification where as water filters through the roots of our forest trees to end up as clean water in our rivers and streams.

Many important nutrients are continuously cycled in our ecosystems and are thus always available for instance, oxygen, water and phosphorous which is essential for plant growth.

Therefore knowing how these cycles operate and are maintained, is necessary for the existence of all organisms on the planet.

Finally there is global ecology, which is the study of the patterns of the worldwide circulation of energy and nutrients and the factors that control it. The concept of global ecology is best explained using an example. One well known example is the clearing of the Amazon rainforest, one of the major natural sinks or absorbers of carbon dioxide in the world. Therefore as the forest decreases more carbon dioxide remains in our atmosphere contributing to global warming and in turn climate change.

I hope this short article has shown that the study of ecology as one moves from the level of a single organism to the planet, all components both living and non-living are vital for the continued survival of our planet, and on a more selfish note, the existence of humans.