Density-dependent factors are influences on a population's growth that depend directly on the population's density (size).
Density-dependent factors exert a stronger influence as a population becomes more crowded. These factors primarily affect birth and death rates. Here's a breakdown:
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Competition: As a population increases, individuals compete more intensely for limited resources such as food, water, shelter, mates, and sunlight. Increased competition can lead to decreased birth rates and increased death rates.
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Predation: Predators may focus more intensely on a particular prey species as that prey species becomes more abundant. This can lead to higher death rates in the prey population.
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Disease: Diseases often spread more rapidly and easily in dense populations because individuals are in closer proximity. This increased transmission leads to higher mortality rates.
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Parasitism: Similar to disease, parasites can spread more easily in dense populations, weakening individuals and increasing mortality.
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Waste Accumulation: In dense populations, the build-up of toxic waste products can reach harmful levels, affecting survival and reproduction.
Density-dependent factors can have either a positive or negative correlation with population size. Negative correlations are more common, where the limiting factor increases with population size, thus limiting growth. Positive correlations are less frequent.
In summary, density-dependent factors act as regulators of population growth by responding to population density itself.
