Question

select the correct answer.

a farmer began a new method of reducing grain spills. this reduced the number of mice on the farm. the number of snakes in the surrounding area decreased at the same time. the snakes depended on the mice that lived in the field. whats the likely reason the snake population decreased?

• the number of snake predators increased.
• the number of mice increased.
• the number of mice decreased.
• the pesticides affected the snakes.
• a new breed of mice moved into the field.

Explanation:

Analyze the ecological relationship

Using the Predator-Prey Interactions knowledge point
The text states that "The snakes depended on the mice that lived in the field." This establishes a direct predator-prey relationship where mice are the prey (food source) and snakes are the predators.

Identify the limiting factor

Using the Limiting Factors knowledge point
The farmer reduced grain spills, which "reduced the number of mice on the farm." Since snakes depend on mice for food, a reduction in the prey population directly limits the food supply available to the predators.

Determine the cause of population decline

A decrease in food availability (fewer mice) means the carrying capacity for snakes decreases, leading to a decline in the snake population. Therefore, the likely reason the snake population decreased is that the number of mice decreased.

Evaluate the given options

• "The number of snake predators increased": No evidence is provided to support an increase in snake predators.
• "The number of mice increased": This contradicts the premise that the number of mice was reduced.
• "The number of mice decreased": This directly aligns with the premise and explains the lack of food for the snakes.
• "The pesticides affected the snakes": The text mentions a "new method of reducing grain spills," not pesticides.
• "A new breed of mice moved into the field": There is no mention of a new breed, and a new breed would likely increase or stabilize food supply rather than decrease the snake population.

Answer:

• The number of snake predators increased.
• The number of mice increased.
• The number of mice decreased. (Correct answer)
• The pesticides affected the snakes.
• A new breed of mice moved into the field.