BI102 General Biology

Spring 2008

Dr. Brian K. Penney

Goulet 2320

603 641-7149

bpenney@anselm.edu

Brian K. Penney 's web page

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1. Populations: general concepts

   • A population is a group of individuals of a single species that are potentially interbreeding. These individuals are typically influenced by the same suite of biotic and abiotic factors.

   • Spatial descriptors include: Density (individuals per unit of space) and dispersion (how individuals are spaced within their area; clumped, random, uniform or even)

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2. Population growth will depend on relative birth and death rates, as well as age and sex structure.

   • Mortality and survivorship: can be described through life tables or survivorship curves (KNOW THESE TYPES Fig 36.3).

   • Factors limiting population growth are density-dependent (such as breeding success) or density-independent (e.g. weather).

   • Growth can be predicted via idealized models of population growth such as the exponential population growth model and the logistic population growth model. The logistic model includes both growth rate (r) and carrying capacity (K).

   • Population levels may wander unpredictably or have cycles driven by abiotic factors, predation rates, or a lag in predator's numerical response.

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3. Life histories are selected to match current conditions.

   • Life history characteristics such as number of offspring, timing of reproduction, body size and degree of parental care comprise a species' life history.

   • Strategies range from being optimized for high growth under unlimited resources (r-selected) to being optimized for population maintenance near carrying capacity (K-selected).

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4. Practical applications of population studies include:

   • sustainable resource management of fisheries/wildlife resources to find maximum sustained yields

   • studies to predict resource needs for the future, as human populations have grown exponentially for the last 400 years. An important international consideration is whether countries have undergone the demographic transition, when both mortality and birth rates slow.

Copyright 2007-2008, Brian K. Penney

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