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A group of students summarized information on five great extinction events. Five Great Extinction Events Mass Extinction Time of Extinction Organisms Greatly Reduced or Made Extinct End of the Ordovician period 443 million years ago Trilobites, brachiopods, echinoderms, and corals End of the Devonian period 354 million years ago Marine families on tropical reefs, corals, brachiopods, and bivalves End of the Permian period 248 million years ago Trilobites, mollusks, brachiopods, and many vertebrates End of the Triassic period 206 million years ago Mollusks, sponges, marine vertebrates, and large amphibians End of the Cretaceous period 65 million years Ammonites, dinosaurs, brachiopods, bivalves, and echinoderms The students are sampling a site in search of fossils from the Devonian period. Based on the chart, which of the following would be the most reasonable plan for the students to follow?

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?