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Which of the following statements best expresses the concept of punctuated equilibrium? a) Small variations gradually accumulate in evolving lineages over periods of millions of years. b) Random mating ensures that the proportions of genotypes in a population remain unchanged from generation to generation. c) Stability is achieved when selection favors the heterozygote, while both types of homozygotes are at a relative disadvantage. d) Evolutionary changes consist of rapid bursts of speciation alternating with long periods in which species remain essentially unmodified. e) Under competition for identical resources, one of the two competing species will be eliminated or excluded.

Which of the following statements best expresses the concept of punctuated equilibrium? a) Small variations gradually accumulate in evolving lineages over periods of millions of years. b) Random mating ensures that the proportions of genotypes in a population remain unchanged from generation to generation. c) Stability is achieved when selection favors the heterozygote, while both … Read more

Evolution is one of the unifying themes of biology. Evolution involves change in the frequencies of alleles in a population. For a particular genetic locus in a population, the frequency of the recessive allele (a) is 0.4 and the frequency of the dominant allele (A) is 0.6. (c) Identify a particular environmental change and describe how it might alter allelic frequencies in this population. Explain which condition of the Hardy-Weinberg principle would not be met.

Evolution is one of the unifying themes of biology. Evolution involves change in the frequencies of alleles in a population. For a particular genetic locus in a population, the frequency of the recessive allele (a) is 0.4 and the frequency of the dominant allele (A) is 0.6. (c) Identify a particular environmental change and describe … Read more

On a large volcanic island, researchers are studying a population of annual herbaceous plants. Which of the following observations best supports the prediction that speciation will occur within the existing plant population? a) Individuals of the species sometimes reproduce asexually by producing runners. b) Lava has separated the population into two areas: an upland forest and a lowland marsh. c) Multiple groups of birds depend on the fruit produced by the plants as a source of food. d) The plants produce more seeds during warm summers than they do during cool summers.

On a large volcanic island, researchers are studying a population of annual herbaceous plants. Which of the following observations best supports the prediction that speciation will occur within the existing plant population? a) Individuals of the species sometimes reproduce asexually by producing runners. b) Lava has separated the population into two areas: an upland forest … Read more

A scientist is studying a population of lizards with three different color phenotypes. The color phenotype is controlled by a single gene with two alleles: an incompletely dominant allele A and a recessive allele a. The scientist collected data on the color of 100 lizards. The data are shown in the table. RED AA 75PURPLE Aa 15BLUE aa 10 To test the hypothesis that the population is at Hardy-Weinberg equilibrium, the scientist performed a chi-square test. Which of the following values is closest to the chi-square value the scientist calculated? a) 0.1 b) 1.9 c) 18.3 d) 23.1

A scientist is studying a population of lizards with three different color phenotypes. The color phenotype is controlled by a single gene with two alleles: an incompletely dominant allele A and a recessive allele a. The scientist collected data on the color of 100 lizards. The data are shown in the table. RED AA 75PURPLE … Read more

Goats and sheep belong to the same family but different genera. While they often live together in the same pastures, the hybrid offspring that are occasionally produced between the two species rarely survive. When such a hybrid does survive, it is usually sterile. Which of the following best explains the mechanism that maintains reproductive isolation between goats and sheep? a) Gene flow is prevented because the two species belong to different trophic levels and therefore do not share a food source. b) Habitat isolation creates a prezygotic barrier between the two species. c) The males of one species and the females of the other species are fertile at different times. d) The two species have a different number of chromosomes, resulting in a postzygotic barrier.

Goats and sheep belong to the same family but different genera. While they often live together in the same pastures, the hybrid offspring that are occasionally produced between the two species rarely survive. When such a hybrid does survive, it is usually sterile. Which of the following best explains the mechanism that maintains reproductive isolation … Read more

Figure 1 compares two models of speciation, A and B. Which of the following best explains how the ecological conditions are likely to be different in the two models? a) In model A the ecological conditions remain unchanged for long periods of time and then change drastically; in model B the ecological conditions change drastically from generation to generation. b) In model A the ecological conditions remain unchanged; in model B the ecological conditions change gradually over long periods of time. c) In model A the ecological conditions are changing drastically from generation to generation; in model B the ecological conditions remain unchanged. d) In model A the ecological conditions change gradually over a long period of time; in model B the ecological conditions remain unchanged for long periods of time and then change drastically.

Figure 1 compares two models of speciation, A and B. Which of the following best explains how the ecological conditions are likely to be different in the two models? a) In model A the ecological conditions remain unchanged for long periods of time and then change drastically; in model B the ecological conditions change drastically … Read more

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