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15 Cards in this Set
- Front
- Back
Current extinction rates
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- may be several thousand times higher than historical rates
- disproportional selection of older, taller and longer-lived organisms -humans exploit resources at a fast rate |
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Determining when to take
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Close to max - good for harvesting because the organism can't sustain or increase numbers
Close to zero - bad, potential Allee effects |
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Optimal harvesting time
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- occurs at the point of maximum growth
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Maximum sustainable yield (MSY)
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-the point where population growth is at its maximum and ideal for take
- rates > MSY lead to a loss of organisms from natural processes (competition, predation) and density dependent effects - rates < MSY could lead to a loss of too many individuals, Allee effects, interbreeding depression |
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Models for calculating yield
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- max profit is a function of the population density and species longevity
- typically these models don't take spatial data into acount -spatial distribution is important to understand the cost of harvest (How spread out is the target species) |
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effects of overexploitation
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-can lead to a trophic cascade
-extinction -loss of diversity |
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What is known about climate change?
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- greenhouse gases are increasing
- average world temp is increasing - sea level is rising - temperature sensitive systems and processes have changed! |
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Greenhouse effect
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sunlight penetrates and the light waves are transformed into infrared radiation
-radiation cannot escape and is reflected back to Earth |
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Basic Issues
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- climate varies naturally but "climate change" refers to an additional, rapid change induced by humans
- increase several degrees C/century - will disrupt the foundations of life on Earth -ecosystems have evolved within a narrow band of climatic-environmental conditions |
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Indicators of climate change
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- temperature
-climatic disasters: weather, hurricanes etc |
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ENSO events
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- effect of climate change on the frequency and amplitude of El Nino events
- increased risk of drought and flood |
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Ecological impacts of climate change
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-morphological changes will be required to deal with physiological changes - how quickly can species adapt?
- change in species composition - shifts in species abundances and assemblages - timing and phenology changes - range shifts *lots of uncertainty |
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implications of climate change
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- extinctions: predictions of amount and severity varies
-increased disease -spread of invasive species - habitat loss -changes in biotic interactions |
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conservation strategies and climate change
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- species may move due to range and abiotic shifts but reserve boundaries won't shift
- boundaries will no longer protect species |
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Albedo effect
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surfaces, like snow, reflect radiation back from the earth
- loss of snow leads to an increase in absorption of solar radiation |