An ecosystem is defined by the interactions between the living and non-living things in any given area. These interactions result in a flow of energy that cycles from the abiotic environment and travels through living organisms via the food web.

This energy flow is ultimately transferred back to the abiotic environment when living organisms die and the cycle begins all over again.

Abiotic factors are the non-living components of an ecosystem. These include:

• air
  
• water
  
• wind
  
• soil
  
• temperature
  
• sunlight
  
• chemistry

Abiotic factors interact with each other as much as the biotic, or living organisms, interact.

Living organisms adapt to their biotic environment to survive. Mammals in cold environments need thick fur to stay warm. Reptiles sit on hot rocks in the sunlight to warm their bodies. Animals such as termites, ants and rabbits dig burrows in the ground for shelter.

One of the most critical interactions in an ecosystem between the biotic and abiotic environment is photosynthesis, the base chemical reaction that drives most life on earth. Plants and algae use sunlight, water and carbon dioxide to create the energy they need to grow and live via photosynthesis. An important by-product of photosynthesis is oxygen, which animals need to breathe.

Plants and algae also absorb the essential vitamins and minerals they need to live from their environment. Animals eat plants and algae and absorb these vitamins and minerals. Predators eat other animals and obtain the energy and nutrients from them. This is how nutrients cycle from the abiotic environment through the biotic world.

Within an ecosystem, there are three different categories of organisms: producers, consumers and decomposers.

Producers are organisms such as plants and algae that create energy through photosynthesis. Consumers eat other organisms for their energy. Decomposers break down dead plants and animals and return nutrients to the soil.

There are four main types of species interactions that occur between organisms in an ecosystem:

• Predation, parasitism and herbivory - In these interactions, one organism benefits while the other is negatively affected. * Competition - Both organisms are negatively affected in some way due to their interactions. * Commensalism - One organism benefits while the other is neither harmed nor gains. * Mutualism - Both organisms benefit from their interactions.

Red fox (Vulpes vulpes) and hare (Lepus europaeus) interactions are an excellent example of predator-prey dynamics. The hares consume grasses, then the red foxes predate the hares. The grasses are negatively impacted by the hares while the hares benefit by getting a meal. Foxes then benefit by eating the hares.

Commensalism examples are more difficult as it is hard to prove whether the other animal benefits or is negatively impacted.

For example, Remora fish ride other fish and sharks and then eat their leftover food. The sharks and large fish are said not to be affected by the presence of the Remora as they ride them and then eat the leftover food. This interaction would be classed as competitive if Remora fought their hosts for food instead of waiting until they were finished.

Plants with bird or butterfly pollinators are good examples of mutualistic interactions. Plants benefit by having their flowers pollinated so they can reproduce. The butterflies and bird pollinators benefit as they get a delicious nectar meal.