74. A mutation in mice leads to overgrowth of the Sertoli cells, so they span across the diameter of the seminiferous tubules. What phenotype would you expect to see? (A) infertility due to lack of mature oocytes (B) overproduction of sperm, so they clog the bulbourethral gland (C) overproduction of testosterone (D) infertility due to lack of mature sperm entering the epididymis

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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