A Lichen Is Growing on a Tree Trunk

question 42

Multiple Choice

A lichen is growing on a tree trunk. The lichen gains height and exposure to sunlight for photosynthesis. The tree is not harmed by the lichen but does not benefit either. The relationship between the lichen and the tree is

• A)commensalism.
• B)mutualism.
• C)parasitism.
• D)interference competition.

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Definitions:

Average Total Cost

The total cost divided by the quantity produced, reflecting the per unit cost of production.

Average Variable Cost

The variable cost per unit of output, which includes costs that vary with production, such as materials and labor.

Economic Profit

The net outcome of subtracting all expenses, both overt and hidden, from a corporation's aggregate earnings.

Short Run

A period during which at least one of a firm's inputs is fixed, limiting the firm's ability to adjust to changes in market demand or supply.