The Effects of Zebra

In this lab, you will determine how an invasive species—the zebra and quagga mussel—affects other species in the freshwater lake. Use the animation to help you come up with an answer to the following:

• Why do you see increases and decreases in the invasive species population?
• What are the implications associated with these alterations to the ecosystem as a whole?

The Effects of Zebra and Quagga Mussels Introduced into a Freshwater Lake

As you have learned, population dynamics are caused by the biotic potential of the population and the effects of environmental resistance. When there is minimal environmental resistance impacting a population, it will exhibit a population explosion. One reason for minimal resistance could be factors that no longer regulate a population (e.g., predator decline or resource increases). Another reason for a population explosion is the introduction of an invasive species. Invasive species are species foreign to an ecosystem and are not immediately regulated by the environmental restraints of the particular ecosystem that they invade. This in turn allows their populations to grow seemingly uncontrolled and to displace other indigenous populations. Examples of such an invasive species into North America are dreissenid mussels, commonly known as zebra and quagga mussels. Their introduction into the Great Lakes has caused economic hardship and a reorganization of the ecosystem. This has led, in part, to pollution-causing effects that can be linked to an alga known as Cladophora.

Ecosystems are webs of intricately balanced interactions, what happens when a new species is introduced that uses a disproportionate share of the ecosystem’s resources?

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