1). An ecosystem is MOST likely to return to its original condition after which of these occurs?
A) New predators are introduced to control a pest population.
B) A marsh is filled in to make space for a new parking lot.
C) Flood waters erode the banks of a narrow stream.
D) Tall prairie grass burns after being struck by lightning.
2). In some national parks, controlled fires are maintained by firefighters. Which of these is one of the major reasons for using controlled burns to maintain certain ecosystems?
A) to rid the forest floor of accumulated deadwood and brush
B) to prevent the spread of pests that cause damage to plants
C) to give nonnative plants a chance to colonize the region
D) to replace matured plants with saplings of the same species
3). One reason for the change in the Galápagos ecosystem has been the introduction of species that were not on the island before, such as donkeys, goats, cats, dogs, and insects. How could the introduction of nonnative species MOST likely disrupt the balance of life on the islands?
A) erosion and degradation of the soil in an ecosystem
B) changes in weather conditions which have an impact on fragile life
C) increased tourism which threatens the habitats
D) greater competition for limited food sources