Notes on an Eco-System

These notes were taken from wikipedia and the bbc bitesize websites

An Eco-System is composed of living elements sharing the environment with non-living elements.

 

Small scale (micro) eco system eg a pond

Medium scale (messo) eco-system eg a forest

Large scale (biome) eco-system eg a tropical rainforest

Sunlight is the main source of energy – allows the plants to live which allows herbivores to live which allows carnivores to live (the food chain).

 

The term eco system was coined in 1930 by Roy Clapham, to denote the physical and biological components of an environment considered in relation to each other as a unit.

 

Biomes are defined based on factors such as plant structures (such as trees, shrubs, and grasses), leaf types (such as broadleaf and needleleaf), plant spacing (forest, woodland, savanna), and climate.

 

Influencing Factors:

• Elevation
•  Humidity
•  Drainage
•  Salinity of water
• characteristics of water bodies
• Climate
• Human influences such as grazing, hydric regimes,

 

Introducing new elements, biotic (living) or abiotic (non living) into an eco-system tend to have a disruptive effect. Sometimes this can lead to ecological collapse or "trophic cascading" and the death of many species belonging to the ecosystem in question.

 

Under this deterministic vision, the abstract notion of ecological health attempts to measure the robustness and recovery capacity for an ecosystem; i.e. how far the ecosystem is away from its steady state.

 

Often, however, ecosystems have the ability to rebound from a disruptive agent. The difference between collapse or a gentle rebound is determined by two factors -- the toxicity of the introduced element and the resiliency of the original ecosystem.

 

Ecosystems are primarily governed by stochastic (chance) events.

An ecosystem results from the sum of myriad individual responses of organisms to stimuli from non-living and living elements in the environment. As the number of species in an ecosystem is higher, the number of stimuli is also higher.

 

 Mathematically it can be demonstrated that greater numbers of different interacting factors tend to dampen fluctuations in each of the individual factors. Given the great diversity among organisms on earth, most of the time, ecosystems only changed very gradually, as some species would disappear while others would move in. Locally, sub-populations continuously go extinct, to be replaced later through dispersal of other sub-populations.

 

Stochastists do recognize that certain intrinsic regulating mechanisms occur in nature. Feedback and response mechanisms at the species level regulate population levels, most notably through territorial behaviour. Andrewatha and Birch^[12]suggest that territorial behaviour tends to keep populations at levels where food supply is not a limiting factor. Hence, stochastists see territorial behaviour as a regulatory mechanism at the species level but not at the ecosystem level.

 

 

An ecosystem is an environment containing a community of interdependent plants and animals. Food chains link animals to the plants/animals they eat and the animals that eat them.

 

Ecosystems are made up of both non-living (abiotic) and living (biotic) factors.

• Abiotic factors are the elements of an ecosystem that are non-living. Nevertheless, they still have an affect on the ecosystem. Water, temperature, relief (height above sea level), soil type, fire, and nutrients are all examples of abiotic factors.
• Biotic factors are the living elements of an ecosystem, i.e. plants and animals. All biotic factors require energy to survive. These living organisms form a community within an ecosystem.

 

The community within an ecosystem is linked together by food chains. Biotic factors become linked in a food chain when they eat one another. The start or bottom of a food chain is made up of producers, such as plants and algae. 

These producers are at the bottom as they do not eat other biotic factors for their energy. Instead of taking energy from food, producers get energy by converting it from carbon dioxide and water using sunlight (Photosynthesis).

Consumers eat other organisms to get their energy.

There are four types of consumer:

1.      Herbivores are organisms that eat plant matter (producers) to gain energy.

2.      Carnivores are organisms that eat meat to gain energy.

3.      Omnivores are organisms that eat both plant (producer) and animal (consumer) matter to gain energy.

4.      Decomposers are organisms that feed on the remains of dead plant and animal matter. They help to speed up the process of decay. They also assist in recycling nutrients back to producers in nutrient cycles.

 

In the same way as energy passes through the food system, so do toxins. A toxin is a poisonous substance. When it enters an organism it will be stored in the tissues of that organism.

·         Producers absorb toxins and store them.

·         The toxin will pass to an herbivore when it consumes the contaminated producer.

·         The toxin will pass to a carnivore when it consumes the contaminated herbivore.

·         The toxin will pass to a higher carnivore when it consumes the contaminated carnivore.

 

The more contaminated organisms a carnivore consumes, the more toxins it will amass. This process is called the bioaccumulation of toxins and can have undesirable affects on organisms near the top of a food chain.