Individual mortality is the result of intrinsic (e.g., senescence and morbidity) or extrinsic factors (e.g., environmental stochasticity and natural disasters). For populations, mortality can be an important regulatory mechanism when deaths resulting from biotic (usually density dependent) or abiotic (usually density independent) factors limit population growth. Density-dependent and density-independent mortality factors were first described by Howard and Fiske in 1911, and were referred to as 'facultative mortality' and 'catastrophic mortality', respectively. A central issue in understanding population dynamics is the attempt to separate and identify the roles of density-dependent and density-independent processes in determining the growth, predictability, and variability of population abundances. However, because observations of death in nature are often difficult to pin down to a single cause, it has been a challenge to isolate their separate effects.
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Preparing for Armageddon, Natural Disasters, Nuclear Strikes, the Zombie Apocalypse, and Every Other Threat to Human Life on Earth. Most of us have thought about how we would handle various types of scenarios that could signal the end of the world. There are plenty of movies on the subject, psychological papers, and even survivalists that are part of reality TV shows. Perhaps you have had dreams about being one of the few left and what you would do in order to survive.