BIOL 422 Lecture Notes - Lecture 8: Complex Dynamics, Habitat Destruction, Density Dependence

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Happens because populations composed of individuals (male, female, young, old, barren, fertile) Rule of thumb: not so important in population > 100 or so, but depends on breeding structure. E. g. some individuals reproduce a lot, some do not. Environmental stochasticity: change in mean vital rate through time. Happens because weather changes, food, predators, etc. change. Habitat loss, pollution, climate change, invasives or harvest. Small populations keep populations small due to stochastic factors. Stochastic variation is random variation in sex and age ratios, environmental conditions or genetic structure. Can lead to reduced survival and/or reproduction, keeping a small population small or nudging it even closer to extinction. Beech tree forests produce mass seed crops every 3-5 years. The more seeds you produce, the more will get past predators. House mice populations surge after the mass crops (time lagged) Stoat populations increase just after the house mice populations (time lagged)

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