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Description
Flashcards by Shareef Akbari, updated more than 1 year ago
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Created by Shareef Akbari
almost 8 years ago
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| Question | Answer |
| What is Rapoport's rule? | As you get closer to the tropics, species' geographical ranges decrease |
| How does Rapoport's rule relate explain the longitudinal gradient of species richness? | Decreased range sizes in the tropics mean that you can pack more ranges in one space, meaning there can be more species in that space, increasing density. Ranges get bigger as you go to temperate areas, so less species in the same space. |
| What are the problems with Rapoport's rule explaining the latitudinal gradient of species richness? | 1. Rapoport's rule itself only works for climate generalists that can live with extreme temperature changes. So organisms that avoid weather by migrating, being ectotherms etc. are not expected to follow Rapoport's rule, and so shouldn't show latitudinal diversity gradient. But they do. 2. Annual climatic variability, which is the cause of Rapoport's rule, is a weak/non-predictor of species diversity 3. There are empirical inconsistencies 4. Rapoport's rule can arise as a sampling artifact (less sampling in the tropics may mean smaller apparent ranges) |
| How is glacial history supposed to explain the latitudinal gradient of species richness? | When North America was covered in ice during the Wisconsinian ice-age, there was low diversity in these areas. The glacial history theory proposes that these areas stayed with low diversity. |
| What are the problems with the glacial history theory in explaining the latitudinal gradient of species richness? | 1. Number of species recovered quickly after glacier retreat. 2. Geographical distributions of species change quickly during climate change, so footprints of glation fade quickly. |
| What is niche conservatism? | Tolerances of an organism tend to stay similar through time. |
| Is climate a good or bad predictor of species richness? Elaborate. | Good, it explains a median of 70% of species richness. |
| How can niche conservatism explain the trend in species richness? | The origins of most organisms are tropical, therefore their tolerances match tropical environments. Because tolerances tend to stay similar over time, less species can handle the different ranges of environmental parameters seen at higher latitudes, and so there are less species that exist at higher latitudes. |
| How does habitat heterogeneity explain the latitudinal gradient in species richness? | Species are limited to certain habitats. If you put more habitats in a certain area, you will have more species. |
| What is the consequence of humans destroying habitats? | It decreases habitat heterogeneity and therefore decreases the number of species. |
| What is the mid-domain hypothesis? | There is an increased number of species at the equator simply because it is in the middle of the earth. |
| Explain how the mid-domain hypothesis come about? | If you use a null model and randomly set down a range, and repeat this many times, the result will be a lot of overlap in the middle, signifying an increased number of species in the middle. |
| What is the problem with the mid-domain hypothesis? | Range boundaries are not only longitudinal |
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