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Survival Factors (Limiting factors (a component of an ecosystem which…
Survival Factors
Limiting factors
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Abiotic factors include environmental conditions – such as light, temperature, salinity, rainfall, wind velocity, soil pH, etc.
Biotic factors include interactions between organisms – either intraspecific (within species) or interspecific (between species)
Law of Tolerance
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As a population is exposed to the extremes of a particular limiting factor, the rates of survival begin to drop
Zones
Optimal zone – Central portion of curve which has conditions that favour maximal reproductive success and survivability
Zones of stress – Regions flanking the optimal zone, where organisms can survive but with reduced reproductive success
Zones of intolerance – Outermost regions in which organisms cannot survive (represents extremes of the limiting factor)
Plant examples
Plant species that are not particularly salt tolerant are called glycophytes – these plants are easily damaged by high salinity
Plant species that are salt tolerant are called halophytes – these plants may become stressed in freshwater environments
Plant types
Cultivation of land for agriculture (e.g. irrigation or grazing) causes the water table to rise and concentrates salt at the roots
This makes it harder for glycophytes to extract water from the soil (also, the uptake of salt can be toxic to the plant)
Understanding salt tolerance for different plant species is therefore critically important to effective crop farming
Animal examples
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Coral properties
Coral polyps receive nutrition from photosynthetic zooxanthellae (an algae) that lives within the polyp’s endodermis
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Increases in ocean temperature cause zooxanthellae to leave the coral tissue, leading to coral bleaching (i.e. > 35ºC)