Final answer:
In a perfectly competitive market, the market demand curve is downward sloping while a single firm’s demand curve is horizontal, reflecting the firm's inability to influence the market price and its status as a price taker.
Step-by-step explanation:
The market demand curve for a good in a perfectly competitive market is downward sloping, indicating that as the price decreases, quantity demanded increases. This reflects the overall market behavior for goods and services. On the other hand, the demand curve for a single competitive firm's product within a perfectly competitive market is horizontal, or perfectly elastic, which means that the firm can sell as much as it wants at the market price but has no power to set the price itself.
In a perfectly competitive market, individual firms are price takers due to the large number of firms and homogenous products, meaning no single firm can influence the market price. In contrast, a monopolistic competitor faces a downward-sloping demand curve, which is more elastic than that of a pure monopolist, reflecting some degree of market power in terms of setting the price. A monopolistically competitive firm is considered a price maker and seeks to produce the quantity of goods where marginal revenue equals marginal cost, allowing them to maximize profits.