Blog

Competition for food would probably be most severe between two

Which of the following is not a potential problem posed by non-native species?

Stickleback fish are found in both marine and freshwater habitats. The marine fish have no scales but have hardened, armorlike plates along their sides. The plates are thought to protect sticklebacks from certain predators. In the late 1980s, sticklebacks from a marine population colonized Loberg Lake, a freshwater lake in Alaska. Starting in 1990, researchers sampled fish from the lake every four years and recorded the armor-plate phenotypes of the male sticklebacks in each sample. The armor-plate phenotypes were categorized as either complete (plates extending from head to tail), partial (plates extending from head to abdomen), or low (a few plates near the head only). The results are shown in the table below. ARMOR-PLATE VARIATION IN THE STICKLEBACK POPULATION OF LOBERG LAKE Percent of Males in the Sample with Each Armor-Plate Phenotype Year Low Partial Complete 1990 1% 2% 97% 1994 45% 14% 41% 1998 58% 16% 26% 2002 76% 15% 9% 2006 90% 6% 4% Which of the following graphs best represents the type of selection most likely operating in the stickleback population of Loberg Lake? The key indicates that a solid line represents Before selection, a dashed line represents After selection, and a downward pointing arrow indicates selection against.

True or false? Disturbance events must be naturally occurring to be considered true ecological disturbances.

Which nutrient cycle is most affected by human overuse of fertilizers?

Data regarding the presence (+) or absence (-) of five derived traits in several different species are shown in the table below. Presence (+) or absense (-) of five derived traits. Species Traits 1 2 3 4 5 V + + + – – W + + – – – X + – – + + Y – – – – – Z + – – – + Which of the following cladograms provides the simplest and most accurate representation of the data in the table?

In community ecology, the “non-equilibrium model” is based on the idea that

The three-spined stickleback (Gasterosteus aculeatus) is a small fish found in both marine and freshwater environments. Marine stickleback populations consist mostly of individuals with pronounced pelvic spines, as shown in Figure 1. Individuals in freshwater stickleback populations, on the other hand, typically have reduced pelvic spines, as shown in Figure 2. Each figure shows an image of a stickleback fish with a genetic structure below it. The left figure is labeled Figure 1. Marine stickleback. A long Pelvic Spine on the fish is labeled. The genetic structure below the fish contains three enhancers, a promoter, and a gene. From left to right, the Enhancer Sequences are labeled Hindlimb, Pituitary, and Jaw. To the right of the Enhancer Sequences is a Promoter with an arrow moving up and to the right, over the top of the Pitx1 gene. The right figure is labeled Figure 2. Freshwater stickleback. A short Pelvic Spine on the fish is labeled. The genetic structure below the fish contains three enhancers, a promoter, and a gene. From left to right, the Enhancer Sequences are labeled Hindlimb, Pituitary, and Jaw. The Hindlimb enhancer is crossed out with an X, and it is labeled Disabled Due to Mutation. To the right of the Enhancer Sequences is a Promoter with an arrow moving up and to the right, over the top of the Pitx1 gene. As represented in Figure 1 and Figure 2, the phenotypic difference between marine and freshwater sticklebacks involves Pitx1, a gene that influences the formation of the jaw, pituitary gland, and pelvic spine. Enhancer sequences upstream of the Pitx1 genetic locus regulate expression of the Pitx1 gene at the appropriate times and in the appropriate tissues during development. Previous studies have found that a mutation in the hindlimb enhancer interferes with the formation of a pronounced pelvic spine. A mutation that affects Pitx1 gene function in all tissue types is most likely to be at which of the following genetic loci?

Which of the following statements best supports the claim that organisms share fundamental processes as a result of evolution?

In the Florida Everglades, Burmese pythons are an invasive species. They were introduced into southern Florida in 1992. These pythons feed on many of the native Florida species, establishing the pythons as the top predator in the environment. By the year 2000, their population had increased dramatically. Figures 1 and 2 display data collected by ecologists studying the results of the Burmese python invasion. Figure 1 shows counts of animals collected from nighttime road surveys in southern Florida, which are used to estimate population size. Figure 2 shows data collected from mosquitoes captured from the wild. DNA sequencing was used to identify the species of blood that the mosquitoes had in their stomachs, identifying various hosts used by the mosquitoes. The categories are labeled along the horizontal axis as follows: White-Tailed Deer, Raccoon, Coyote, Cotton Rat, and Rabbit. Each category has two bars indicated on it, which are each labeled 1996 and 2011 respectively. Each bar has an error range indicated. The vertical axis is labeled Number Observed, per 100 kilometers of road, and the numbers 0 through 3, in increments of 1, are indicated. The data for each bar is presented as follows. Note that all values are approximate. White-Tailed Deer. 1996, 2.7, plus or minus 0.3. 2011, 0.8, plus or minus 0.4. Raccoon. 1996, 1.2, plus or minus 0.2. 2011, 0. 4, plus or minus 0.2. Coyote. 1996, 1.2, plus or minus 0.4. 2011, 0.7, plus or minus 0.3. Cotton Rat. 1996, 0.65, plus or minus 0.2. 2011, 2.5, plus 0.5, minus 0.1. Rabbit. 1996, 1.7, plus or minus 0.3. 2011, 1.3, plus or minus 0.25. Figure 1. Comparison of observations of selected mammals in 1996 and 2011. The horizontal axis is labeled Year, and the years 1979 and 2016 are indicated. The vertical axis is labeled Host Use, in percent total bloodmeals, and the numbers 0 through 90, in increments of 10, are indicated. The 4 line segments are each determined by two points, and are labeled as follows: Cotton Rat, Human, White-tailed deer, and Raccoon. Each line segment is described as follows. Note that all values are approximate. All line segments begin in 1979 and end in 2016. The Cotton Rat line segment is above the Human line segment and crosses the White-tailed deer line segment. The Human line segment crosses the White-tailed deer and Raccoon line segments. The White-tailed deer line segment is above the Raccoon line segment. The line segment labeled Cotton rat begins at the point 1979, comma 15 percent, and moves upwards and to the right to end at the point 2016, comma 80 percent. The line segment labeled Human begins at the point 1979, comma 0 percent, and moves upwards and to the right to end at the point 2016, comma 10 percent. The line segment labeled White-tailed deer begins at the point 1979, comma 30 percent, and moves downwards and to the right to end at the point 2016, comma 2 percent. The line segment labeled Raccoon begins at the point 1979, comma 10 percent, and moves downwards and to the right to end at the point 2016, comma 0 percent. Figure 2. Change in host preference by Culex cedecei between 1979 and 2016. Numbers do not add up to one hundred percent because these represent a subset of all the host species. In 1996, the native Culex cedecei mosquitoes in southern Florida preferentially took blood meals from white-tailed deer and raccoons. It was predicted that changes in host population size would alter these host preferences. Additionally, it is known that cotton rats are often infected by the Everglades virus, which normally exists in animals, but is capable of infecting humans. Ecologists predict that increased feeding on cotton rats by C. cedecei may significantly increase the tendency of this virus to infect humans. Based on the data, which of the following most accurately matches a potential change with its predicted effects on the southern Florida ecosystem?