BIO 200 Lecture Notes - Lecture 30: Swallowtail Butterfly, Temperate Climate, Species Richness
1 Dec 2017
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Document Summary
Species richness = the number of species present. Evenness = the relative abundance of the species. Species richness increases with area: the latitudinal gradient. Ecologists noticed there are more species of a type in the tropics than at the poles (example: swallowtail butterfly diversity more at equator) (example: mollusks as well) (example: amphibians and mammals as well) Potential hypotheses for the cause of the gradient: climate stability. Seasons are hard to handle seasons are disturbances -> hard for species to survive: increased competition. Tropics are a benign environment can provide for a lot of species. Organisms can share without depleting resources for the other. Overlap of niches and less tight packing: increased predation. Predators can lower competition and increase diversity. More species in tropics because there are more predators in the tropics (major logical problem not true: increased energy. Oligocene eocone-miocene climate shift -> cooling down (very cold poles, and limited tropical zones)
