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In aquatic environments
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In terrestrial environments
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Light
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Penetration decreases as depth increases, as the light is reflected, scattered or absorbed. Animal and plant distribution is influenced by the availability of light.
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Is readily available in most terrestrial environments depending on shade provided by living (eg. trees) or non-living (eg. rocks, caves) things. The amount of light available is important for plant growth.
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Availability of water
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Water is readily available, but access to this water sometimes depends on osmotic factors.
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Availability varies, as it depends on rainfall or groundwater.
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Availability of ions
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Marine (saltwater) environments contain dissolved ions including sodium and chloride.
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Ions are available in the soil. Soil type influences the diversity and growth rate of plants.
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Availability of gases
Both carbon dioxide and oxygen are important gases for living organisms.
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Limited availability. Dissolved oxygen increases with decreasing temperature and decreases with depth.
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Are readily available in the air. Air contains about 20% oxygen and 0.03% carbon dioxide.
The availability of gas may be a limiting factor at high altitudes.
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Buoyancy
The upward force that a fluid exerts on an object less dense than itself.
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The buoyancy effect of water is much greater than that of air. Water offers support to both plants and animals, from kelp to whales and jellyfish. This is important as it allows them to maintain their shape and function effectively.
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Plants and animals need to support themselves as the buoyant effect of air is so small.
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Viscosity
Viscosity is a measure of a fluid's (gas or liquid) resistance to flow
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Water has a low viscosity but it is more viscous than air.
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Air has a very low viscosity.
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Temperature
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Experience less variation than terrestrial temperatures.
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Large variation in temperature. Temperature experiences daily and seasonal variations.
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Pressure
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Increases as depth increases. For every 10 metres of depth, the pressure is that of one atmosphere.
For example at10m below the surface, water pressure is twice that pressure on the earth’s surface. At 20m below the surface, the water pressure is three times that of pressure at the earth’s surface.
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Decreases as height above sea level increases. Can also vary over time. Breathing of animals can be influenced by changes in pressure.
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