The graphs illustrate elk and aspen numbers over several decades in Yellowstone National Park.They show major human management actions (removal and return of wolves; hunting of elk).Given this information, describe how biotic factors affected the community structure of Yellowstone National Park during this century.List each biotic factor and its effect. 
Definitions:
Variable Selling
Costs related to selling that vary with the level of sales activity, such as commissions or shipping charges.
Production Capacity
The maximum output that a business can produce in a given period under normal working conditions.
Fixed Manufacturing Overhead
Costs associated with manufacturing that do not vary with the level of production, such as rent, salaries, and insurance.
Variable Cost
Costs that change in proportion to the level of production or sales volume.
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