One of the oldest known mammalian fossils belongs to a small furry species, Hadrocodium wui, that lived 195 million years ago. For the following 100 million years, only a small number of groups of mammalian fossils are found in the fossil record. By 65 million years ago, the non-avian dinosaurs were extinct. By 55 million years ago, there were 130 mammal genera, including 4,000 different species that occupied a wide variety of habitats. Which of the following best describes the cause of the rapid increase in the number of mammalian species between 65 and 55 million years ago?

In humans, one allele of the APOE gene, called APOE–ε2, can result in a high tolerance of cholesterol. Cholesterol is a vital substance for humans but may lead to heart disease in an older adult with a history of high cholesterol diets. High cholesterol diets are becoming more prevalent in the United States. Currently only about 2% of humans carry the APOE–ε2 allele. Which of the following states a valid null hypothesis about the future distribution of APOE alleles in future generations in the United States?

Which of the following pieces of evidence best supports the hypothesis that birds and crocodilians (crocodiles and alligators) are more closely related to each other than they are to other organisms?

The wing of a bat, the flipper of a whale, and the forelimb of a horse appear very different, yet detailed studies reveal the presence of the same basic bone pattern. These structures are examples of

A survey reveals that 25 percent of a population of 1,000 individuals have attached earlobes (are homozygous recessivefor the trait). For the following questions, assume that the population fits the parameters of the Hardy-Weinberg law. Unlike most natural populations, this population is best characterized in which of the following ways?

One facet of the study of the origin of life focuses on the nature of the first genetic material. Figure 1 describes a possible scenario, known as the RNA World Hypothesis, that could have led to the evolution of our modern-day genetic material. This hypothesis states that the first genetic material was RNA, not DNA, and a transitional period led to the emergence of DNA as the storage molecule for genetic material. The model has 3 columns and 3 rows. The column labels from left to right are: column 1: The R N A World, column 2: Evolution of the Modern World, column 3: The Modern World. The information is as follows: Column 1, row 1: Ribonucleotides produce R N A, row 2: R N A uses R N A to produce R N A, row 3: Amino Acids use R N A to produce Protein. Column 2, row 1 is blank, row 2: R N A uses Protein to produce D N A. row 3 is blank. Column 3, row 1 is blank, row 2: D N A uses Protein to produce D N A, then vertically from row 2 to row 3, D N A uses Protein to produce R N A and R N A uses Protein to produce D N A, then R N A uses Protein to produce Protein. A scientist wishes to provide experimental evidence to support the model shown in Figure 1 by demonstrating the ability to synthesize an RNA molecule. Which of the following is an alternative hypothesis that can be tested to support the World Hypothesis?

Which of the following is NOT correct about a keystone species?

In a small group of people living in a remote area, there is a high incidence of “blue skin”, a condition that results from a variation in the structure of hemoglobin. All of the “blue-skinned” residents can trace their ancestry to one couple, who were among the original settlers of this region. The unusually high frequency of “blue skin” in the area is an example of

From left to right, the model begins with two virus structures. The structure on top is an Avian Influenza Virus, with the R N A Molecules and Glycoprotein X labeled. The bottom structure is a Human Influenza Virus, with the R N A Molecules and Glycoprotein Y labeled. A right-facing arrow points from each virus to a Pig Respiratory Tract Cell with D N A Molecules labeled. A right-facing arrow points from the Pig Respiratory Tract Cell to a New Strain of Human Influenza Virus, with the R N A Molecules and Glycoprotein Z labeled. The cells lining the respiratory tract of pigs have receptors for both avian and human influenza viruses. Based on the model above, which of the following best describes the origin of the new strain of human influenza virus?

Ellis-van Creveld syndrome is a recessive genetic disorder that includes the characteristics of short stature and extra fingers or toes. In the general population, this syndrome occurs in approximately 1 in 150,000 live births. In a particular isolated population, however, the incidence of this syndrome among live births is 1 in 500. Assume that both the isolated population and the general population are in Hardy-Weinberg equilibrium with respect to this syndrome. Which of the following best describes the difference between the frequency of the allele that causes the syndrome in the general population and the frequency of the allele in the isolated population?