Barrons AP Environmental Science

(Marvins-Underground-K-12) #1

  1. (C) Environmental resistance or limiting factors consists of all factors in an
    environment that limit a population’s ability to increase in numbers.
    Predation, competition for resources, disease, limited food and space, etc.,
    all work to hold a population in check. Environmental resistance can be
    either density-dependent or density-independent. Factors that are density-
    dependent are stronger when a population has a higher density (more
    crowded). Examples would include predation, parasitism, disease, and
    competition for space or food. Density-independent factors (usually abiotic)
    will kill organisms—whether they are crowded or not. Examples would
    include floods, storms, earthquakes, fire, etc. In nature, biotic potential and
    environmental resistance work together to level out population numbers to
    an amount that can be supported by the environment. When environmental
    resistance “pushes down” on J curve growth, the curve levels into what is
    known as an S curve (or sigmoid curve) and reflects a balanced community.

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