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27 Cards in this Set
- Front
- Back
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Community Disassembly |
the ongoing process of non-random species losses and declines |
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Global extinction |
the total disappearances of a species |
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local extinction |
the disappearance of a species from part of its natural range |
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extirpation |
extinction of a population rather than of an entire species |
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Ecological Extinction |
the reduction of a species to such low abundance that, although it is still present in the community, it no longer interacts significantly with other species. |
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natural extinctions |
little empirical data |
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past extinctions |
estimated from fossil records (problematic) |
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natural extinction rates vs speciation rates |
probably balanced each other out over much geological time (one extinction per million species-year) |
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how do extinction rates differ for different groups? |
marine inverts- new species every 2-20 years birds- estimate of extinction rate of one species every 83.3 yrs |
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mass extinction |
an extinction event representing a sharp decrease in the # of species on Earth on a short period of time |
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5 major mass extinctions |
cretaceous-tertiary extinction (65 mys)- dinasaurs End Triassic Extinction (200 mys) Permian Triassic Extinction (250 mya) Late Devonian Extinction (364 mya) ordovician-silurian extinction (440 mya) |
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How does genetics cause extinctions? |
Demographically: birth rate < death rate Stochasticity: demographic stochastity (small pop) - environmental stochatstity (catastrophic events) -genetic Stochasticity (mutations/loss) Allee Effects: Factors that cause reduction in the growth rate of small populations as they decline (ex. via reduced survival or reproductive success) |
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Role of Stochasticity in Extinctions |
Stochasticity:
-demographic stochastity (small pop) - environmental stochatstity (catastrophic events) -genetic Stochasticity (mutations/loss) |
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Role of Allee Effects in Extinctions |
factors that cause a reduction in thegrowth rate of small populations as they decline (e.g.,via reduced survival or reproductive success).
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Current and future extinction rates |
past: 1/1000 species went extinct every millennium Present: up to 1000X greater Future: 10X higher than current rate |
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Sixth mass extinction on earth |
currently experiencing the sixth mass extinction on earth |
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How are humans causing extinctions? |
predation (food, fur, collecting, pest eradication) Habitat Destruction (habitat loss, fragmentation, degradation) Pollution, contamination, toxcicity Introduced Species Climate Change |
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Anthropocene |
earths most recent geological time period (epoch) - atmospheric, geologic, hydrologic, and bioshperic evidence of human-influenced alteration |
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Ecological Correlates of Extinction Risk |
- small population size -rare/endemics (small range) -synchronous populations -specialists (vs. generalists) -high trophic position - low reproductive output -large body size |
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Extinction Vortex: Extinction Threshold |
occurs when a marginal change causes a change in the probability of extinction from 0--> 1 |
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Extinction Vortex |
small population-->inbreeding and genetic drift -->loss genetic variability -->reduction in individual fitness and population adaptability -->lower reproduction -->higher mortality --> Smaller population |
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Extinction Dept |
future extinctions that arise from past events |
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Co-extinction |
the loss of one species leads to the loss of another and a chain of extinctions |
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Community Disassembly |
the ongoing process of non-random species losses and declines - the order in which species disappear from a community depends in their vulnerability to specific stressors and on traits associated with inherent susceptibility to decline |
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Why is community disassembly non-random |
in not a random process, but follows 'disassembly rules'- principles that govern the order of species loss |
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Disassembly Rules |
1. initial species loss 2. the driver of extinction/loss 3. Rate of disassembly 4. The environmental context/conditions 5. Chance events (stochasticity) |
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Community Disassembly Overview |
- can start with the addition or loss of a single species -includes losses in genetic diversity, extripation of popualtions, and species-level extinctions -is typically non-random -proceeds through interaction webs as cascading extinctions -outcomes can be delayed (extinction dept) |
