The population of a cactus species in a particular area has two to seven spines with an average of four spines per square centimeter of surface area.Cacti with fewer than four spines per square centimeter are more easily eaten by the wild boars thriving in the area.Over time,the population of this cactus species in this area have an average of six spines per square centimeter of surface area.This is an example of

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The increase in average number of spines suggests a shift towards individuals with more spines, which is an example of directional selection. The cacti with fewer than four spines are being selectively eaten, which is likely driving this directional shift towards individuals with more spines. Disruptive selection would involve favoring extreme values on either end of a trait distribution, and stabilizing selection would involve favoring intermediate values. There is no evidence of genetic drift in this scenario.

The Population of a Cactus Species in a Particular Area