Final answer:
Non-native plants and animals can have a negative impact on a watershed ecosystem by outcompeting native species, disrupting the food chain, and altering the physical characteristics of the habitat.
Step-by-step explanation:
Invasive species are non-native organisms that, when introduced to an area out of their native range, threaten the ecosystem balance of that habitat.
Non-native plants and animals can have a negative impact on a watershed ecosystem by outcompeting native species for resources, disrupting the food chain, and altering the physical characteristics of the habitat.
For example, the zebra mussel, a non-native invasive species, has caused significant damage to aquatic ecosystems by attaching to and damaging native species, clogging water intake pipes, and changing water quality.