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Unformatted text preview: that (A) species richness increases along the gradient from A to E (B) species richness decreases along the gradient from A to E (C) discrete communities are formed at sites D and E (D) discrete communities are formed at sites A, C, and D (E) no discrete communities are formed along the gradient GO ON TO THE NEXT PAGE. Unauthorized copying or reuse of any part of this page is illegal. 34 107. Acid rain damage depends on the buffering capacity of the soils in a given region. Damage has been greatest where the soil layer is (A) thin and contains little calcium and magnesium (B) thin and contains abundant calcium and magnesium (C) thin and contains abundant calcium but little magnesium (D) thick and contains abundant calcium and magnesium (E) thick and contains little calcium and magnesium 108. Nitrogen is a major environmental pollutant of groundwater in many parts of the world. What is the major cause of this nitrogen accumulation in groundwater? (A) Excessive use of nitrogen fertilizers (B) Destruction of nitrifying bacteria, which results in soil nitrogen remaining as NH4+ (C) Excess soil moisture, which causes ammonification or denitrification (D) Presence of sandy-textured soil (E) Lack of moisture in the topsoil, which attracts nitrogen to the subsurface and groundwater 109. The phosphoglucomutase (Pgm) locus in California populations of Nuttall’s white-crowned sparrow has allelic frequencies of 0.8 and 0.2, respectively, for the alleles Pgm-A and Pgm-B. What is the probability that two heterozygous individuals will mate, given that Pgm is in Hardy-Weinberg equilibrium? (A) (B) (C) (D) (E) 0.01 0.10 0.16 0.32 0.60 GO ON TO THE NEXT PAGE. Unauthorized copying or reuse of any part of this page is illegal. 35 B RR Initial frequency Adaptive value Frequency after selection Relative genotype frequency after one generation of selection p2 1 p2
p2 1 sq 2 1 GENOTYPES Rr 2pq 1 2pq rr q2 1−s q2 ( 1 − s )
q2 1 Total p2 + 2pq + q2 1 − sq2 1 2 pq
sq 2 s sq 2 1 110. For a trait controlled by a single-locus, two-allele system with complete dominance, p is the gene frequency of R, the dominant allele, q is the gene frequency of r, the recessive allele, and s is the selection coefficient against the recessive homozygote. The table above indicates the effects of natural selection on genotype frequencies over one generation. After one generation of such selection, the relative frequency of the recessive allele, r, will be equal to (A)
1 2 2 pq q2 1 s (B) 1 2 2 pq 1 q2 1 sq s
2 s (C) q2 1 1
1 2 sq 2 pq 1 2 (D) p2 sq 2 q2 (E) 1 2 2 pq GO ON TO THE NEXT PAGE. Unauthorized copying or reuse of any part of this page is illegal. 36 111. Sewall Wright’s metaphor of evolution on an adaptive landscape describes a population as occupying a field of genotypes graded by contours delimiting gene combinations of equal fitness. The evolutionary mechanism most likely to move a population consistently “uphill” toward adaptive peaks on this landscape is (A) (B) (C) (D) (E) chance directed mutation natural selection gene flow between populations genotypic recombination 115. In a certain species of lizard, there are two color morphs associated with a single lo...
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