the nonnative zebra mussel was first found in a lake near detroit in 1988. By 1989, it had colonized all Great Lakes waterways. Which scenario is the most likely reason that the zebra mussels have successively colonized Great Lakes waterways?
A. Nonnative species are more aggressive than natives in competing for limited resources.
B. Invasion species are not held in check by predators and agents of disease that have always been in place for natives.
C. Nonnative species have a higher reproductive potential tan native species.
D. Humans always select which species will out-compete the nuisance native species.
A. Nonnative species are more aggressive than natives in competing for limited resources.
B. Invasion species are not held in check by predators and agents of disease that have always been in place for natives.
C. Nonnative species have a higher reproductive potential tan native species.
D. Humans always select which species will out-compete the nuisance native species.
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Except for the word "always" in D, these methods have all been "used" by various invasive species. Further, not all nonnative species are more aggressive then natives, but this is often the case with invasive nonnative species. Again, not all nonnative species have higher reproductive rates than native, but, again, this is often the case with invasive nonnative species.
In the case of the zebra mussels, B is probably the best answer because, Wikipedia says, "Since no North American predator or combination of predators has been shown to significantly reduce zebra mussel numbers, such spread would most likely result in permanent establishment of zebra mussels in many North American waterways." The Wikipedia article also points out that the introduction of the mussels is believed to have been "inadvertently ... in the ballast water of ocean-going ships traversing the St. Lawrence Seaway."
In the case of the zebra mussels, B is probably the best answer because, Wikipedia says, "Since no North American predator or combination of predators has been shown to significantly reduce zebra mussel numbers, such spread would most likely result in permanent establishment of zebra mussels in many North American waterways." The Wikipedia article also points out that the introduction of the mussels is believed to have been "inadvertently ... in the ballast water of ocean-going ships traversing the St. Lawrence Seaway."