75. A scientist is studying several areas along an elevation gradient. Her study involves prescribed burns (purposefully set, low-intensity fires) in the different areas, followed by a comparison of the type and abundance of organisms that colonize them over the next ten years. What scale best describes her study? (A) Physiological ecology (B) Ecosystem ecology (C) Organismal ecology (D) Community ecology

76. Most bird species that form flocks show a negative relationship between flock size and individual vigilance (i.e., the larger the flock, the less often an individual lifts its head to scan the surrounding environment). However, some bird species have shown a positive relationship between flock size and individual vigilance. The positive relationship is particularly strong when flocks are space-constrained, such as in small ponds or fields. What is the most likely explanation for this? (A) As flock size increases, the number of "cheaters" increases, so individuals must spend more time scanning for predators. (B) As flock size increases, the risk for interference and aggression between members increases, so individuals must scan for both conspecifics and predators. (C) As flock size increases, the risk of predation for any given member increases, so individuals must spend more time scanning for predators. (D) As flock size increases, mating opportunities decrease, so individuals must spend more time scanning for potential mates.

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