ENV234H1 Lecture Notes - Lecture 15: Intermediate Disturbance Hypothesis, Ecological Niche, Species Complex
14 Nov 2016
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About 1. 75 million known species: described during 250 years of efforts by taxonomists. 75% are animals (72% are insects; 4% are vertebrates, most are fish) Estimated total: 3 30 million species. E. g. , fumigation of tree canopy (large scale) vs. malaise trap: spend time identifying insects. Problems identifying species: cryptic species hard to identify, could look similar to a known species, but have different interactions and do different things, ecotypes or species debatable. Problems defining individual fungi, spruce, aspen etc. Biological diversity species diversity richness: number of species: evenness: relative abundance of species; much more difficult concept. Greater diversity: more species with an approximately even number of each species. Most species are rare; there are very few dominant species. E. g. , krebs (2012) on moths: many species only had 1 individual, common species had more individuals, but less number of species. One environmental factor studied looking at the performance of species on a gradient, dependent on a factor (e. g. , temperature, ph, water)
