Earth and Life Science Practice Test

Invasive species reduce biodiversity mainly by outcompeting native species for limited resources. When a non-native organism establishes itself, it often has advantages—faster reproduction, a broader diet, or tolerance to a wider range of conditions—that let it dominate shared resources like food, space, or mating opportunities. As the invader thrives, native species struggle to compete, decline in numbers, or disappear locally. With natives diminished, the variety of species in the ecosystem drops, and genetic diversity within remaining populations can also shrink.

Other options don’t describe this common effect: increasing genetic diversity of natives would raise biodiversity, not decrease it; stabilizing food webs implies a balanced system that supports diversity, not a loss; increasing habitat area tends to support more species, increasing biodiversity, not reducing it.