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19 Cards in this Set
- Front
- Back
A species is considered rare if
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It has a narrow geographical range
It occupies one or a few specialized habitats It is found in small populations |
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Rabinowitz’s rarity is based on
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the geographic range of a species (extensive versus restricted)
habitat tolerance (broad versus narrow) and local population size (large versus small). |
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Species that have an extensive geographic range, broad habitat tolerance and large local population size
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(house sparrow, dandelions, crabgrass)
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Restricted geographic range, broad habitat tolerance and large local populations
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Galapagos medium ground finch, Monterrey pine
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Extensive geographic range, narrow habitat tolerance and large local populations
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California grey whales, Freemont cottonwood
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Primack poses the question: What makes species vulnerable to extinction?
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One aspect is certain, rare species are more vulnerable to extinction than species that are common
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By definition, common species are ________some part of their range
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abundant in
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Extensive geographic range, broad habitat tolerance and small local population sizes
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tigers and the grassfern – Asplenium septrionale
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Restricted geographic range, narrow habitat tolerance and large local populations
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fish crows, Haleakala silversword
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Restricted geographic range, broad habitat tolerance and small local population size
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Tasmanian devil and Welwitschia mirabilis
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Extensive geographic range, narrow habitat tolerance and small local populations size
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Northern Spotted Owl, Pacific yew [Taxus brevifolia])
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Restricted geographic range, narrow habitat tolerance and small local population sizes (
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Mountain Gorilla and Pritchardia monroe, Wollemi pine
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First of all, let us characterize rare by determining what all rare species share:
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Rare species occupy a specialized habitat
Rare species have a narrow geographic range Rare species characteristically have small populations |
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An ________ species is one with a special type of rarity
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endemic
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endemic species
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Species found naturally in a single geographic area and nowhere else
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____are endemic to planet earth, _____ are endemic to west Africa, ____are endemic to south eastern US
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Humans
bonobos the Venus-flytrap and the pitcherplants |
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Endemics of the United States
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Dionaea of North Carolina venus flytrap
Sarracenia from eastern US pitcherplant |
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Which are the species most vulnerable to extinction?
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Species with narrow geographic ranges – any destruction of their habitat is likely to decrease population sizes, disrupt meta-population structure, and directly impact numerous individuals. (Birds on oceanic islands, fish species restricted to one watershed, etc.)
Species with few populations – habitat destruction wreaks havoc because it could easily extirpate the few isolated populations. (Pupfish in desert Southwest, Gold-cheeked warbler that nests only in Texas Juniper ash woods) Species that have perpetually small populations usually have low genetic variation and may be subject to repeated genetic bottlenecks that decrease genetic variation. The cheetah is notorious for this as are other top predators Species in which population size is declining have critical demographic connections between stages in their life history which make them vulnerable. Many species of primates in Africa and South America…. This is particularly true where these primates are principal constituents of “bushmeat” which is the next category. Species that are hunted or harvested by people. |
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The IUCN categories of conservation status
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