Five new species of bacteria were discovered in Antarctic ice core samples. The nucleotide (base) sequences of rRNA subunits were determined for the new species. The table below shows the number of nucleotide differences between the species. Nucleotide differences between species Species 1 2 3 4 5 1 — 3 19 18 27 2 — 19 18 26 3 — 1 27 4 — 27 5 — Which of the following phylogenetic trees is most consistent with the data?

The graph below shows changes in a population of wild sheep that were introduced to the island of Tasmania in the early 1800’s. The horizontal axis is labeled year from 1820 to 1940 with tick marks in increments of ten. The vertical axis is labeled number of sheep in thousands from zero to two thousand five hundred, with tick marks in increments of 500. The population curve starts at zero in 1820, increases slowly then increases rapidly to two point two five million by 1850. This increase is enclosed in a bracket. After 1850 the population curve fluctuates between two point two five million and one point two five million, with a horizontal dashed line through the middle of these population fluctuations. The graph indicates that the sheep population most likely is

Scientists have found that the existing populations of a certain species of amphibian are small in number, lacking in genetic diversity, and separated from each other by wide areas of dry land. Which of the following human actions is most likely to improve the long-term survival of the amphibians?

Students observed the distribution of different color phenotypes in northern ravine salamanders (Plethodon electromorphus) before and after a spring flood. The data are shown in Table 1. Table 1. Salamander Distribution Before and After a flood Salamander Distribution Before the Flood (n) Salamander Distribution After the Flood (n) Black phenotype 13 7 Dark-brown phenotype 25 14 Light-brown phenotype 6 3 Which of the following is an appropriate null hypothesis regarding the phenotypic frequencies of this population of salamanders before and after the flood?

Many scientists claim that the synthesis of the first organic molecules from inorganic precursors was possible because of the highly reducing atmosphere found on primitive Earth. Which of the following is an appropriate null hypothesis that could be used when investigating the claim?

Maximal transcription of the lac operon requires

Tay-Sachs disease is a rare inherited disorder caused by an autosomal recessive allele of the HEXA gene. Affected individuals exhibit severe neurological symptoms and do not survive to reproductive age. Individuals who inherit one copy of the allele (Tay-Sachs carriers) typically show no symptoms of the disorder. The frequencies of Tay-Sachs carriers in the general population of North America and in three different subpopulations are presented in the table. For general population the frequency is 0.004. For subpopulation 1 the frequency is 0.037. For subpopulation 2 the frequency is 0.035. For subpopulation 3 the frequency is 0.020. Which of the following is an ethical question about Tay-Sachs disease that cannot be answered using scientific methods?

Iridium is an element that is rare on Earth but commonly found in meteorites. A scientist believes that the first organic molecules may have come to Earth on meteorites 3.6 billion years ago. Which of these would be an appropriate null hypothesis to test related to whether meteorites hit the Earth 3.6 billion years ago?

There is an S-curve with five points labeled A through E along the curve. A is the beginning of the curve when the slope is zero and there is a low number of individuals, B is next on the curve with a higher number of individuals when the slope is one, C is next on the curve with a higher number of individuals at the point where the curve transitions from a rapidly increasing number of individuals to a slowing rate of growth. D is the next point on the curve when slope is again at one, and E is the final point on the curve with the highest number of individuals and a slope approaching zero. Which point on the curve in the diagram above best represents the carrying capacity of the environment for the population shown?

Retroviruses have an RNA genome. HTLV-1 is a lysogenic retrovirus that establishes a latent infection in human cells. By which of the following mechanisms does infection by a retrovirus such as HTLV-1 most likely cause long-lasting genetic changes to host cells?