Frage | Antworten |
Species Richness | number of species |
Species Diversity | a measure of number and evenness of species |
Simpson's Index (D) D=1-sump(i) | probability of picking two organisms at random that are different species |
Why are there more species in the tropics than in any other area on earth? | 1. Time Hypothesis 2. Climate Hypothesis 3. Area Hypothesis 4. Competition Hypothesis 5. Predation Hypothesis |
Time Hypothesis | tropical communities have had more time for speciation than temperate or polar communities -Draw Graph Examples |
Climate Hypothesis | more species can adapt to favorable climate in the tropics than harsh climate in other areas |
Area Hypothesis | tropical zones contain more area on the globe than temperate area |
Competition Hypothesis | species are more specialized in the tropics, allowing more species to coexist -Draw Graphs |
Predation Hypothesis | predation is stronger in the tropics allowing more species to coexist |
Field Experiment of Predator Mediated Coexistence | Starfish: -Prey species: mussels, limpets, chitons, barnacles, snails -With Starfish removed, mussels excluded other species, lowering species diversity -Starfish present, resulted in greater species diversity as they preferred mussels |
Observational Field Study of Disturbance Mediated Coexistence Example 1 | Rocky Intertidal Disturbances: -With logs absent, mussels excluded other species -Effects of predation and disturbance on species diversity are similar -Caveat: predation and disturbance cannot not be too intense |
Intermediate Disturbance Hypothesis Graph | . 1: competitive exclusion by dominant species 2: disturbance mediated coexistence 3: extinctions cause by too much disturbance |
Observational Field Study of Disturbance Mediated Coexistence Example #2 | Algae on Intertidal Boulders: -Draw experiment graph -FREQUENCY DISTURBANCE -Small boulders turn over more frequently than large boulders 1: Competitive exclusion by red algae; 2: Coexistence of green and red; 3: Only green present |
Experimental Field Study of Disturbance Mediated Coexistence | Snails Eating Algae: -emergent substrate versus tide pools -built cages on rocks that excluded snails and contained algae -in tide pool, highest number of algae with intermediate number of snails (too many snails=extinction & too few=algae exclude other algae) -emergent substrate had decreased algae due to snails and wave disturbances -SNAILS PREFFERED COMPETITIVE ALGAE IN TIDE POOLS AND INFERIOR COMPETITOR ON EMERGENT SUBSTRATES |
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