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BGYC63 Oct04

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Biological Sciences
Ivana Stehlik

BIOC63 Oct04 Threats to BIodiversityinvasive species and thier effects on local communities Invasive Species A Definition and scale of invasion Native species a particular species that historically occurred or currently occurs in an ecosystem Introduced species a species that is new to a habitat that has immigrated that didnt occur before it is just new dont say the effectInvasive species a species that is also new to the area but has a negative effect to the native species Biological Incation the movement of species from one area to another new areasince humans started to move around the amount of species invasion has risen the more people travel the more species get moved aroundespecially after the industrial revolition when you look at the makeup 22 of species in canada is alien and in ontario 32 is alienwhen you compare this to islands it is even higherin Ascension it is 82 generally in island settings the percentage is much higher because once they get there they cant leavelooking at the local scale Ontario we can see that within the invasive species plants have the highest percentage on a global and also on a local scale the number of invasive plants is always much higher than any other living organismswhen we look at proportion of invasive plants ontario is 1B Typical course of Invasionpathways of plant introduction in Canadaof the 141 species of plants introduced intentionally were introduced as ornamental or landscaping plants gardeningthen as agricultural cropof the 120 species of plants introduced unintentionally more than 75 were introduced with plant products contaminants in seed wood productsthe nonnative species that turn into invasive species follow similar patternsfirst they are in very low numbers for a long time lag phase which can take from 10200 yearsand most of nonnative species stay in this lag phase and never take offbut some take into the log phase where they increase in number until they inhabit all area that they can C Reasons for success of Incadoers Enemy Release Hypothesis Why are invasive species so successful Enemy Release Hypothesis ERthey escape from their enemies so the native species still with thier competitors are frequently outcompetedin a native area all are fed relatively equally but in a nonnative area the invasive
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