本题目来源于试卷: Continuity and Change D.10 Natural Selection，类别为 IB生物学
[单选题]
In a population of finches,+how +yc;6 o9fyit /wu the frequency of finches w 0-b,aaf yuxz3v bmb3* qw/sy/ith large beaks has increased relative to the frequenw /bv3mbfu-y/ s0a3 b ayx*,qzcy of finches with small beaks. What could have been a cause for this?
A. A decrease in the competition for food
B. A change in the availability of seeds
C. Selection in favour of individuals with small beaks
D. An increase in the heritability of beak size
参考答案: B
本题详细解析:
If the frequency of large beaks has increased relative to the frequency of small beaks, the population has likely undergone natural selection. In natural selection, a particular pressure in the environment promotes the survival and reproduction of organisms with a trait that makes them best able to contend with that environmental pressure. In the case of the finches, an increase in the frequency of large beaks could result from a change in the availability of seeds. For example, an increase in the availability of large seeds would select for finches that have the beaks that are best suited to cracking those seeds (i.e., large beaks). As large-beaked finches survived and reproduced at a greater rate than small-beaked finches, the frequency of finches with large beaks would increase. A decrease in the competition for food (Choice A) would reduce the selection pressure on beak size, and so would likely not result in a change in the relative frequency of large and small beaks. Selection in favour of individuals with small beaks (Choice C) would increase the frequency of finches with small beaks relative to the frequency of finches with large beaks. The heritability of beak size (Choice D) cannot change. The heritability of a particular trait is determined by the genes underlying the trait, and so is a fixed factor.
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