Lec16_08BIEB102

Lec16_08BIEB102 - BIEB102 Announcements Final Exam: 10 Dec...

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Unformatted text preview: BIEB102 Announcements Final Exam: 10 Dec (F) at 1130-230 in York 2622 Format similar to previous exams Last part of course - 120 points Second part of course - 50 points First part of course - 30 points For the old material focus on concepts You are unlikely to be tested on specific details of case studies from the first part of the course. All equations that you might need will be provided on the test. Near De Luz, San Diego County (fire Oct 07; blooms Apr 08) BIEB 102 Lecture 16: diversity Measuring diversity Factors that influence local diversity Alpha, beta and gamma diversity Species-area relationships Latitudinal diversity gradients Functions of diversity Diversity Overview Communities differ in terms of their species composition and diversity How many species are there? Why are there more species in the tropics? Do communities that differ in diversity have different functional properties? e.g., stability, productivity, resistance to invasion What role does history play in determining local diversity? Measuring diversity Species vary in relative abundance One of the important differences among species within communities is their relative abundance. In most communities a few species are numerically dominant while many are rare and represented by relatively few individuals. Ecologists depict relative abundance relationships in rank order graphs. Ricklefs Figure 21.18 Ricklefs Figure 21.19 Note that x-axis reversed in text. Measuring diversity Species ordered by decreasing abundance Species differ in their tolerances to the physical environment and in how they interact with other species. i.e., species niches differ As a result, the relative abundances of species within communities are often very different. Purple - Vascular plants in fir forests Green - Vascular plants in deciduous forests Blue - Forest birds Measuring diversity How do ecologists measure diversity? Richness = the number of species in a community Simple metric, but does not take into account differences in relative abundance Disparities in relative abundance affect diversity estimates in two ways: ( 1) total number of species in a sample will depend on sample size This makes it difficult to compare species counts for two areas that have been sampled with different degrees of effort. (2) individual species probably should not contribute equally to diversity The functional importance of a species in a community will often be related to its abundance. Measuring diversity D = Simpsons index = 1 / p i 2 p i = the proportion of each species in the total sample Imagine a community with three equally common species: D = 1 / [(1/3) 2 + (1/3) 2 + (1/3) 2 ] = 1 / [(3/9)] = 1 / [(1/3)] = 3 Measuring diversity D = Simpsons index = 1 / p i 2 p i = the proportion of each species in the total sample Imagine a community with three equally common species: D = 1 / [(1/3) 2 + (1/3) 2 + (1/3) 2 ] = 1 / [(3/9)] = 1 / [(1/3)] = 3 Now imagine a community with one common species and two rare species:...
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Lec16_08BIEB102 - BIEB102 Announcements Final Exam: 10 Dec...

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