BIO 126 Lecture Notes - Lecture 3: Primary Succession, Frederic Clements, Biome
21 Mar 2016
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Differing views of communities: organismic model by clements. Individuals, populations, and communities have a relationship to each other that resembles the associations found between cells, tissues, and organs: individualistic model by gleason. Community is an assemblage of species coexisting primarily because of similarities in their physiological requirements and tolerances. Principle of species individuality: each species is distributed according to its own physiological needs and population dynamics. Competition does not create distinct vegetational zones: imagine a moisture gradient on a mountain slope . One group of interacting species gives way at a sharp boundary to another assemblage (clement"s organismic model) Competing species exclude each other but do not become organized into groups of species. Competition does not result in sharp boundaries but adaptations result in similar distributions. Centers and boundaries of populations are scattered along gradient (gleason"s individualistic model) Results support 4th hypothesis: each species is distributed in its own way, according to its genetic, physiological, and lifecycle characteristics.
