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Flashcards in Patterns of biodiversity Deck (11)
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1
Q

biodiversity

A
  • the variety of life

- species richness

2
Q

Historical theories of biodiversity

A
  • stability-time hypothesis
  • museum hypothesis
  • unstable/stable environmentalist
3
Q

Equilibrium theories

A
  • greater habitat diversity = greater resource gradient length & available niche space
  • large population sizes with large geographic ranges have reduced risk of extinction
  • but boreal forest also covers very large are but has low diversity than Mediterranean
4
Q

Northern Canada vs Amazon Basin

A
  • poor soils, vary flat/uniform topography and uniform habitats
  • but massive difference in biodiversity
  • little seasonal change in temp, moisture, daylight etc.
5
Q

if environment is stable

A
  • best adapted species can cause competitive exclusion of less adapted species
  • results in decrease biodiversity
6
Q

Environmental disturbance

A
  • creates spatial heterogeneity
  • environmental conditions not constant for long enough to allow dominant species to drive other to extinction
  • too much disturbance leads to extinction of sensitive species or those with small populations
  • rainforests can withstand occasional fires but not frequent ones, eventually it would turn into savanna
7
Q

intermediate disturbance hypothesis

A
  • biodiversity will be highest in systems in which the rate of displacement of species by competition is low and the rate of disturbance is also low
8
Q

competition hypothesis

A
  • evolution in mid-high latitudes driven by physical stresses (temp & moisture)
  • evolution in the warm, moist tropics driven by interspecific competition, leads to evolution of species with specialised niches
  • greater species packing in a given area
  • may apply to certain animal groups but unclear how it applies to tree species
  • also, unclear why competition should be greater in low latitudes than high latitudes
9
Q

Predation hypothesis

A
  • high number of predator and parasite species generates high biodiversity by keeping prey populations low
  • prevents competitive exclusion of one prey species by another
  • consistent with pattern of tropical tree species
10
Q

why does this pattern exist

A
  • no one theory is adequate explanation, so maybe a combination of reasons
  • temp and moisture probably key
11
Q

productivity or energy hypothesis

A

Tree species:

  • strong correlation between species richness and evapotranspiration
  • strong correlation between evapotranspiration and NPP
  • more energy available for photosynthesis in the tropics than high latitudes
  • more NPP = more biomass = more complex vegetation structure
  • more complex vegetation structure = more niches & micro habitats for animals
  • diversity of micro-climates