Biology - a Local Ecosystem

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A Local Ecosystem
Biotic and Abiotic
* Biotic Factors – living organisms (trees, birds, predators etc…) * Abiotic Factors – non living variables (temperature, oxygen levels etc…) Abiotic Characteristics of Environments
Characteristics| Aquatic| Terrestrial|
Viscosity (measure of a medium’s resistance to an object moving through it)| HIGH VISCOSITYDifficult for organisms to move through| LOW VISCOSITYEasy for organisms to move through| Buoyancy (amount of support experienced by an object)| HIGHGives support to plants and animals. May help maintain shape| LOWPlants and animals need to be able to support themselves| Temperature (Depends on intensity of sun’s radiation)| Heats up and cools down more slowly than air. Heat loss/gain is not a problem| Temperatures vary a great amount.| Gas Availability | Diffusion is generally slower, with more gases available at lower temperatures. Oxygen concentration decreases with depth| Gases are freely available and diffusion is rapid| Water Availability| Readily available – osmotic differences of fresh and salt water are important| Varies, land organisms are prone to dehydration| Light Penetration| Decreases with depth, and thus affects availability of plants| Readily available, but can be affected by dense plant growth.| Distribution and Abundance

* Distribution – WHERE an organism is found. Usually uneven throughout the ecosystem. * Organisms are found where the environment favours them: * Survival rate is high
* Predation is low
* Requirements for survival are met

* Abundance – HOW MANY organisms are present in an ecosystem. Not the same throughout the environment, and changes over time: * INCREASES due to births and immigration
* DECREASES due to deaths and emigration
* Other factors affecting abundance:
* Abiotic:
* Light
* Wind strength
* Rainfall
* Temperature...
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