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what are diversity gradients
the # of species in an area may vary based on various gradients . ex latitude
what is the evolutionary speed hypothesis
- diversity is affected by length of un-interupted evolutionary time
- - ex. tropics have been less disturbed in recent history than temperate zones
What is the geographic area hypothesis?
the larger an area is, the more diverse habitats and thus species possible
-relationship between area and richness is not always supported. boundaries hard to define
patterns of bio diversity: what are interspecific reactions
higher diversity due to greater inter-specific competition & predation rates
What is the ambient energy hypothesis
- higher available energy generates/maintains higher global diversity gradients
- -climate dictates available energy (light, temp, water)
- -closer to equator = more light, heat, moisture
what is the intermediate disturbance hypothesis
- disturbance is a factor that affects local species diversity
- -states that if communites exist i equilibrium (no change from coming going)
- -competition dictates taht one or two competative species should dominate.
- -disturbance knocks communities out of equilibrium
what can act as a disturbance?
- change in physical factors (temp,light, etc)
- catastrophe (fire,flood,etc)
- allows other species to get a foothold(predator mediated competition)
- to much disturbance is NOT a good thing
- too little disturbance isnt good = competative exclusion
- intermediate disturbance = highest species diversity
General physical structure -
communites are also characterized by general physical form
what is the community vertical structure?
- based on growth form of plants
- - size of plants, variation in branching heights, leaf density. this is associated with vertical production of light.
- Provides framework for animals, who adapt to certain structures
Species within communities are constrained by their f________ niche
the range of t_________ exhibited by species influences their p_______ in a community
what is succession?
- the universal process of directional change in vegetation over time
- -progressive change in groups of species in an area.. with one group replacing a previous group
give an example of how a forest succession might happen
- clear cut->shrubs/saplings->pole woods-> mature forest
- only way to go backward is disturbance
what are the two types of succession
primary succession and secondary succession
when does secondary succession occur?
give an ex.
- after small-scale disturbances
- - agricultural field abandoned, fire, treefall
when does primary succession occur?
give an ex.
- occurring after large-scale disturbance
- -succession of a new sterile area
- -mt st helens ash sterilized area
which happens faster, primary succession or secondary succession
- primary much slower than secondary