lecture note 19 for BGYB50

LECTURE 19: - Competition between cells, organisms, populations, and species can either be: (a) direct (also known as “contest” or “interference” competition) or (b) indirect (also known as “resource” or “scramble” competition) - When individuals of the same species compete, we speak of intraspecific competition; if individuals of different species compete, we call it interspecific - Biological competition is defined by: (a) the direct or indirect “struggle” for a limiting resource (e.g. space, food, sexual partner), (b) reduction of resource availability due to the activity of the competing organisms, and (c) mutual (!) impact upon growth, survival or fecundity (genetic fitness!), i.e. both “partners” in a competition scenario are affected (a -/- interaction) - Plants can engage in direct competition as well, e.g. through allelopathy, the production of chemicals that inhibit the germination or growth of neighbouring plants (it is a form of “chemical warfare”; many allelopathically active chemicals are also of medicinal value) - Competition also plays itself out at the cellular level - For competition to become manifest, resources (most often space, food, or mating partners) must be limiting - Central to the understanding of competition, as to so many other things, is the concept of ecological optima and tolerance limits of biological organisms: Because the majority of organisms in a population in principle “like” similar things (e.g. one type of food, spaces with a certain temperature), organisms are forced to compete for the latter when www.notesolution.com population numbers become large (intraspecific competition; the resulting reduction in rates of population increase is described in the logistic growth equation) - Ultimately, adaptive radiation into different niches is the natural consequence of ongoing pressure of competition (e.g. tree warblers, flight patterns of migratory birds, Darwin finches) www.notesolution.comLECTURE 19: - Competition between cells, organisms, populations, and species can either be: (a) direct (also known as contest or interference competition) or (b) indirect (also known as resource or scramble competition) - When individuals of the same species compete, we speak of intraspecific competition; if individuals of different species compete, we call it interspecific - Biological competition is defined by: (a) the direct or indirect struggle for a limiting resource (e.g. space, food, sexual partner), (b) reduction of resource availability due to the activity of the competing organisms, and (c) mutual (!) impact upon growth, survival or fecundity (genetic fitness!), i.e. both partners in a competition scenario are affected (a -- interaction) - Plants can eng