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9 Cards in this Set
- Front
- Back
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Latitudinal Diversity Gradients |
Species diversity increases from poles to tropics (North to South) (S America tropical forest every 3km^2 300 species) 30-50 in a temperate forest |
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Why is their high species diversity in the tropics |
No recent glaciations (no disturbance allowing diversity to continue) Stable climate (allow more to specialize in specific area leading to low extinction rates) High productivity (warmer and wetter climates lead to more resources) niche conservatism - more and distinctive resources (fruits, insects, plants) - more possible habitats (=close packing of species) and specialization ("own little world") - Vertical stratification: emergents, high and low canopies, shrubs, forest floors |
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Niche conservatism |
Organisms stay in their areas (habitats) and won't move out even if an extinction frees up another area |
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Trophic Structure of Tropical Forest |
Habitat complexity (Large variation and amounts of distinctive resources and habitats) Leads to Divergence/diversification of species (Many different types of resources that can be used and so species can live in close proximity) Leads to microhabitats (due to the habitat diversity) Have narrowly defined niches (narrow range of resources to use etc) Many species (individuals) coexisting |
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Contradiction of Niche Conservatism and how does it help explain the latitudinal species diversity gradient |
Birds of a Southern origin follow niche conservatism Birds of a Northern origin don't follow niche conservatism and some move to the south Helps explain the diversity gradient since is shows there is more migration south than north |
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Why does this contradiction of niche conservatism exist |
Tropical birds Take longer to mature, live longer, have fewer offspring Therefore have a lower basal metabolic rate not equipped physiologically to handle the lower temperatures Can't expand ranges to colder climates (the North) |
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What were the results for bird migration with the Panama Land Bridge Connection formation and what were previous hypothesises |
Previous Hypothesis: Birds can fly so connection didn't change anything Recent data: Bird migration changed in a similar way to mammals Great American Interchange Species interchanged but in an assymetrical ratio (more North America animals flourished in S America so that half of S America's mammals have origins in the North) |
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Late Pleistocene Origins Model explanation for species diverging |
Glaciers occurred in the Late Pleistocene Lead to species being pushed down Isolation and Fragmentation Speciation occurs Later on when species went back they are different species (eg Western and Eastern versions of similar species) |
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Rejection of Late Pleistocene Origins Model and reasons why |
Recent glaciation caused populations to decrease or go extinct, not cause a lot of speciation (Looking at when the diversions occurred, it only resulted in subspecies) The limited ranges/distributions of species may be caused by: - interspecific interactions - Dependent/Resticted to a limited range of habitat/resource - Can not cohabitat with closely related species (too similar in life style choices) - having limited tolerances to climate etc - chance |
