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Graph with “Cretaceous” labling the first third of the x–axis and “Early Paleogene” labeling the remainder, left to right. The y–axis is labeled “% Relative Abundance.” A solid line representing “Fern Sperm” rises from a point about a third of the way up the y–axis, drops slightly, then rises, and drops sharply to zero the “K–Pg Boundary” (which is labeled as such). It then rises, but only to about half of its highest point before the boundary, then drops, and starts to almost level off slightly lower than it started. A dashed line represents “Angeosperm Pollen Grains,” which starts slightly lower than the “Fern Sperm,” raises to about half the level of the “Fern Sperm,” and drops sharply to zero at the “K–Pg Boundary.” It then rises barely above the x–axis, and remains there to almost the end of the graph, where it rises almost to the level of the “Ferm Sperm. Credit: [Biointeractive.com](Biointeractive.com)”

Students analyze pollen grains and fern spores recovered from sediments taken below and above the Cretaceous-Paleogene boundary. Their results are summarized in the graph. Which of the following conclusions can be drawn from the graph regarding the impact of the mass extinction that took place at the K-Pg boundary on plants?

  1. The mass extinction event reduced the number of ferns and angiosperms.
  2. Based on their reduced pollen counts found in the samples, the mass extinction event clearly reduced the number of ferns and angiosperms.
  3. The mass extinction affected only the ferns.
  4. Ferns were more abundant after the Cretaceous-Paleogene (K-Pg) mass extinction than before.
45

Credit: [Biointeractive.com](Biointeractive.com)
 Graph with “Cretaceous” labling the first third of the x–axis and “Early Paleogene” labeling the remainder, left to right. The y–axis is labeled “% Relative Abundance.” A solid line representing “Fern Sperm” rises from a point about a third of the way up the y–axis, drops slightly, then rises, and drops sharply to zero the “K–Pg Boundary” (which is labeled as such). It then rises, but only to about half of its highest point before the boundary, then drops, and starts to almost level off slightly lower than it started. A dashed line represents “Angeosperm Pollen Grains,” which starts slightly lower than the “Fern Sperm,” raises to about half the level of the “Fern Sperm,” and drops sharply to zero at the “K–Pg Boundary.” It then rises barely above the x–axis, and remains there to almost the end of the graph, where it rises almost to the level of the “Ferm Sperm.”

Analyze the graph and discuss the reasons for the fern spike seen in the early Paleogene, considering ferns were the first plants seen on the ground after the volcanic eruption of Krakatoa and Mt. St. Helens. Propose reasons for the observed increase in fern spores following the mass extinction.

  1. Ferns are considered early colonizers as they grow fast on poor soil and reproduce rapidly. Also, mass extinction gave an opportunity for the surviving species to expand and radiate to occupy vacated niches.
  2. Ferns, having a selective advantage of being early colonizers, grew fast on poor soil and reproduced rapidly, thus replaced angiosperms in the landscape.
  3. Ferns are considered early colonizers as they grow fast on poor soil and reproduce rapidly. Also, mass extinction gave an opportunity for new species to radiate and thereby occupy vacated niches.
  4. Most of the fern varieties became extinct, only a single species survived; therefore, the remaining fern spores had many vacated niches to occupy which lead to an increase in fern numbers.
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Table with column headings, “Mass Extinction,” Time of Extinction,” and “Organisms Greatly Reduced or Made Extinct.” First row: “End of the Ordovician period,” “443 million years ago,” and “Trilobites, brachiopods, echinoderms, and corals.” Second row: “End of the Devonian period,” “354 million years ago,” and “Marine families on tropical reefs, corals, brachiopods, and bivalves.” Third row: “End of the Permian period,” 248 million years ago,” and “Trilobites, mollusks, brachiopods, and many vertebrates.” Fourth row: “End of the Triassic period,” “206 million years ago,” and “Mollusks, sponges, marine vertebrates, and large amphibians.” Fifth row: “End of the Cretaceous period,” “65 million years ago,” and “ Ammonites, dinosaurs, brachiopods, bivalves, and echinoderms.”

A group of students summarized information on five great extinction events.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?

  1. Searching horizontally rock layers in any class of rock and trying to find those that contain the greatest number of fossils.
  2. Collecting fossils from rock layers deposited prior to the Permian period that contain some early vertebrate bones.
  3. Looking in sedimentary layers next to bodies of water in order to find marine fossils of bivalves and trilobites
  4. Using relative dating techniques to determine the geological ages of the fossils so they can calculate the rate of speciation of early organisms.
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Table containing the following information. Below Cretaceous-Paleogene had 102 average number of grains/m2, and morphology of many different shapes. Above Cretaceous-Paleogene had 30 average number of grains/m2, and morphology of a few common shapes.

Students are sorting fossils of angiosperm pollen grains, some recovered from layers below the Cretaceous-Paleogene boundary and some from layers above the Cretaceous-Paleogene boundaries. The pollen grains are sorted by morphology.

The results are summarized in a table.

Can you explain the results?

  1. The mass extinction that took place at the Cretaceous-Paleogene boundaries reduced the total number of organisms, seen by fewer shapes of pollen grains, and led to a loss of diversity, seen by the less number.
  2. The mass extinction that took place at the Cretaceous-Paleogene boundaries reduced the total number of organisms, seen by less number of pollen grains, and led to a loss of diversity, seen by fewer shapes.
  3. The mass extinction that took place at the Cretaceous-Paleogene boundaries reduced the total number of organisms, seen by less number of pollen grains.
  4. The mass extinction that took place at the Cretaceous-Paleogene boundaries led to a loss of diversity, seen by fewer shapes of pollen grains.
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Table with column headings, “Mass Extinction,” Time of Extinction,” and “Organisms Greatly Reduced or Made Extinct.” First row: “End of the Ordovician period,” “443 million years ago,” and “Trilobites, brachiopods, echinoderms, and corals.” Second row: “End of the Devonian period,” “354 million years ago,” and “Marine families on tropical reefs, corals, brachiopods, and bivalves.” Third row: “End of the Permian period,” 248 million years ago,” and “Trilobites, mollusks, brachiopods, and many vertebrates.” Fourth row: “End of the Triassic period,” “206 million years ago,” and “Mollusks, sponges, marine vertebrates, and large amphibians.” Fifth row: “End of the Cretaceous period,” “65 million years ago,” and “ Ammonites, dinosaurs, brachiopods, bivalves, and echinoderms.”

A dig in a farmland soil rich in calcium carbonate reveals the following findings: 1. Numerous shells of bivalves 2. Chips of corals 3. The partial imprint of a trilobite 4. A few vertebrae dated to 250 million years ago. The table of extinction summarizes information on the five major extinction events.

According to the table of extinction, which conclusion about the fossils is most reasonable?

  1. The trilobites were the first animals to conquer land.
  2. The rocks can be dated to the Cretaceous Cretaceous-Paleogene boundary.
  3. The farmland was probably part of the seafloor in the Permian period
  4. The fossils can be dated to the Ordovician period.
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Credit: University of Washington: Department of Atmospheric Sciences
 Graph shown with an x–axis ranging from 160 to 0 labeled “Thousands of Years (B.P.)” and a y–axis ranging from –10 to 4 labeled “Change in Temperature (°C).” The graph has a double-ended arrow spanning most of the domain labeled “Pleistocene.” The graph starts at about (155, –6.5) goes up and down a bit, then spikes to (125, 2), a peak labeled, “Eemian Interglacial.” The line then goes up and down in a jagged fashion in an overall decreasing trend until it hits (20, 0). Then, it dramatically spikes upward in the part of the domain labeled “Holococene.” The peak it achieves is labeled “Present Interglacial” and evens out at about 0 on the y–axis as time continues toward 0.

The average temperatures varied during the Pleistocene as glaciation periods were followed by warm intervals. Using the graph above and your existing knowledge, discuss what happened to woolly mammoths and other cold-adapted megafauna 10,000 years ago.

  1. Habitat destruction due to varying temperatures and over-hunting by humans leading to their extinction.
  2. Sudden increase in temperature and over-hunting by humans leading to their extinction.
  3. Gradual increase in temperature and over-hunting by humans leading to their extinction.
  4. Sudden increase in temperature and in predation by larger mammals leading to their extinction.
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Graph with x–axis labeled “Year” with domain from 1970 to 200 and y–axis “Relative Population Size” with no defined range. The lichen population is shown using a solid line and the caribou population using a dashed line. The lichen population starts at almost twice the caribou population, and is shown on a decline until 1992, when it begins to rise slowly. The dashed line follows a similar path, staying below the solid line, though they almost converge in 1977. The dashed line dropps more suddenly after that point, and runs only slightly above and parallel to the x–axis from 1990 onward, with a slight increase occurring in the late 1990s.

In winter, lichens are the only food for the caribou herds that roam the tundra. As the average temperatures increase with climate change, the lichen are gradually being replaced by shrubs and trees in the southern parts of the tundra. The graph illustrates the changes in abundance of lichens and caribou over time in a regional forest of Canada.Which statement best explains the changes in the caribou population between 1975 and 1980?

  1. The caribou population expanded after the population of lichens dropped.
  2. The decline of the caribou population and the lichen population are not related.
  3. The population of caribou decreased following the drop in lichen availability.
  4. The caribou population was eliminated once the lichens decreased.
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A chain within the food web in the arctic ocean is shown below:

Phytoplankton ─> zooplankton ─> arctic char/cod ─> ringed seal─> polar bear. A chain within the arctic food web on land is shown below: Lichen/shrub ─> Caribou/hare/small rodent ─> fox/lynx/bird of prey

If polar bears move to land to hunt due to loss of sea ice, what will happen to the balance of the food web?

  1. Polar bears, being top predators, will edge out the other consumers without gaining enough calories themselves.
  2. Polar bears, being secondary consumers, will edge out the other consumers without gaining enough calories themselves.
  3. Polar bears, being top predators, will edge out the producers without gaining enough calories themselves.
  4. Polar bears, being secondary consumers, will edge out the producers without gaining enough calories themselves.
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Graph with a y-axis of “Capture of Fish in Million tons” from 0 to 4 and an x-axis in years from 1950 to 2010. The number of northeast cod fluctuates up and down from 2 until it reaches a peak of 4 in 1968 and then fluctuates up and down until it reaches a low of a bit over 1 in 2010. The number of northwest cod fluctuates up and down from 1 until it reaches a peak of 2 in 1968 and then fluctuates up and down until it reaches a low of a bit less than 0.5 in 2010. The number of Pacificcod steadily increases from about 0 until it reaches a steady high of 0.5 in 1968 and holds there through 2010.

Historically, the Atlantic Ocean off Canada and the Northeast of the US has been some of the richest and most popular fishing grounds. Huge factory ships developed in the 1960’s converged on the region from all over the world attracted by the rich catches. The graph shown represents the population of cod in recent years. Based on the graph, what is the likely explanation for the collapse of the northwest cod?

  1. A tropical disease decimated the populations of cod.
  2. Overfishing led to the collapse of the cod population.
  3. The cod population migrated somewhere else.
  4. The cod population is going through its cycle of rise and fall.
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Graph titled “Human Population” showing the population in billions on the y–axis, which ranges from 0 to 8, and the year on the x–axis, with a domain of 1750 to 2000. 1950 is in red with a vertical line extending across the graph stemming from that point on the x–axis. The population rises steadily from just under 1 billion in 1750 to just over 2 billion in 1950, then increases sharply, going to 7 billion by the end of the graph. The overall trend is an exponential growth curve.

Graph titled “Extinctions” showing the number of extinctions (since 1500) on the y–axis, which ranges from 0 to 1,000, and the year on the x–axis, with a domain of 1750 to 2000. 1950 is in red with a vertical line extending across the graph stemming from that point on the x–axis. The number of extinctions in 1750 is 0, which increases, with the rate of increase also increasing, to just under 400 in 1950. After that, it increases to almost 800 in 2000 and continues to increase, though at a slower rate, until the end of the graph.

The following graphs show the changes in the human population and the rate of extinction:Which statement most likely explains how the increase in human population could lead to a decrease in biodiversity?

  1. Every human added to the planet replaces a different species of organism.
  2. The more people inhabiting the planet, the more the average temperature increases, causing loss of other species.
  3. With the increase in population the demands for land, water, food, and energy increase, leading to the destruction of habitat.
  4. Increases in human population reduce the amount of land available for use by all species.