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Exam 1 key posted Office Hours Bonus
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Fig 52.7
Carrying Capacity
stationary phase
exponential growth
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What happens as populations approach their
carrying capacity?
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Fig 52.17
36.4
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2.3
UN Department of Economic and Social
Affairs Population Division (2004)
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Fig 52.8
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CB 55.2
Genetic Diversity
Biodiversity- number of species within an area
Ecosystem Diversity
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Increased numbers of one species can reduce the
population of other species
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Fig54.2
Ecosystems on Earth resources are not evenly
distributed
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Larger areas can support more biodiversity
Fig 53.24b
Islands
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Larger areas can support more biodiversity
bird species
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Water is critical for biodiversity
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Fig 50.28
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Fig 50.28
rain quantity and rain pattern affect
productivity and species diversity
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Removing resources reduces biodiversity
1/10th
1/100th
Australian tree hole communities (leaf litter
supports bugs etc)
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New predators can have an affect throughout the
ecosystem
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Interactions include area, climate, competition,
density...
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Have we overstated the tropical biodiversity
crisis?William F. LauranceTrends in Ecology
EvolutionVol. 22 65-70 February 2007
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Are we on the verge of a massive die-off of
tropical species?
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Changes in Extinctions and Diversity
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Are we on the verge of a massive die-off of
tropical species?
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Increased rural density leads to decreased forest.
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This is because rural slash-and-burn farmers
cause most forest loss.
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The good news? About 2124 of species in the
Asian tropics and 1635 of species in the
African tropics are threatened with possible
extinction.
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Rural populations are expected to decline.
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Substantial areas of agricultural land are likely
to be abandoned, because the population growth
rates of many developing nations are slowing and
because of increasing urbanization. This could
enable significant forest regeneration, which
could help buffer species losses from
deforestation.
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Human vs Natural Disturbances
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Extinction rates are likely to be higher in
biodiversity hotspots
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Fig 55.4
Terrestrial Biodiversity Hotspots
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the 16 hotspots that sustain tropical forest have
already lost, on average, 90 of their forest
cover
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Rainforest clear cutting
CB 55.15
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Not all habitats are equal
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A third to a half of all old-growth species avoid
younger (lt30-year-old) regrowth.
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In many tropical regions, future pressures on
forests will be determined more strongly by
industrial drivers, globalization and
macroeconomic forces than by local population
density.
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Rural populations are expected to decline, but
increased urban population will demand more
resources.
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The precautionary principle maintains that one
should err on the side of caution in conservation
matters.
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We need to evaluate critically the degree to
which regenerating and degraded habitats, which
are increasing dramatically at the expense of
old-growth forests, can sustain tropical
biodiversity
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Why are species going extinct?
Fig 55.6