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. Communities include all populations of all species living within a particular area.

   Physical structure of communities, either due to prevalent forms of vegetation, or the physical characteristics of substrate (particle size, fluid flow, etc.) determines potential species composition.

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2. General considerations of species composition and roles include:

   • biodiversity has two components: richness and evenness. Richness of a habitat changes predictably with area and distance from other populations of species.

   • each species has a particular niche, or role in the community

   • some species become more dominant than others, some to the extreme of being keystone species

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3. Species composition changes over time.

   • disturbance, such as fire, storms, drought removes parts or all of the biological community

   • Communities pass through a series of temporal changes called ecological succession (primary or secondary). Disturbance resets this sequence to an earlier point and is important in maintaining diversity.

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4. Interactions between species affect population and ecosystem dynamics, and include:

   • competition for limited resources. If interspecific, it leads to either competitive exclusion or resource partitioning.

   • predation (including herbivory) can lead to extreme adaptations such as mechanical or chemical defenses, or mimicry, and can be an important factor maintaining diversity.

   • symbiotic relationships include pathogens, parasitism, commensalism and mutualism

   • coevolution can occur between interacting species, especially if the relationship tightly links the population dynamics of the involved species

Copyright 2007-2008, Brian K. Penney

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