Environmental Change DOL

Giant salvinia is a floating fern native to Brazil introduced to Texas as an aquarium plant and is now found in large bodies of water across the state. The invasive plant may be carried to new bodies of water by fishing and recreational boats. It grows quickly, covering large areas of the water's surface. When the plant dies and decomposes, the oxygen content in the water declines. How does giant salvinia affect a Texas ecosystem?

• It promotes the growth of new types of plants.

• It increases the stability of the ecosystem.

• It provides an energy source for the ecosystem.

• It inhibits the growth of native plant species.

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During an extended dry season in an area, the majority of the ground cover dried up. Which description best explains how this would affect the ecosystem in that area?

• The ecosystem would become less stable because the ranges of many organisms would expand and overlap.

• The ecosystem would become more stable because there would be less competition among canopy plants.

• The ecosystem would become less stable because less energy would be available to it from the decrease in producers.

• The ecosystem would become more stable because organisms in higher trophic levels would be able to find prey more easily.

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The San Marcos salamander, Eurycea nana, is a light reddish-brown translucent salamander about 2-5cm in length. It is found only in Spring Lake and a portion of the San Marcos River. Which human activity would most likely decrease the ability of the salamanders to survive?

• Increasing water consumption that decrease the flow of clean water from the springs that feed the river.

• Public transportation that reduces the number of automobiles that contribute to pollution runoff into the river.

• Tourism that helps fund the educational programs related to river ecosystem conservation.

• The addition of a new food source into the river that limits competition for resources.

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A scientist monitors two ecosystems over time: Ecosystem A, with high biodiversity, and

Ecosystem B, with low biodiversity. Both ecosystems experience a drought event in Year 5. The

graph shows the plant biomass (kg/m2) over time for both ecosystems. Based on the graph, how does biodiversity contribute to ecosystem stability after an environmental

disturbance?

• High biodiversity helps ecosystems recover more quickly after disturbances

• Low biodiversity ecosystems always have higher biomass than high biodiversity ecosystems.

• The drought event caused both ecosystems to recover at the same rate.

• Ecosystem A’s recovery proves that biodiversity prevents biomass loss entirely.

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A team of researchers conducted a study on a coastal wetland known for its high biodiversity. They discovered a drastic decline in the population of a key predator species due to pollution. What potential effect could this have on the ecosystem's stability?

• Increased stability as prey populations decrease

• Reduced stability due to an increase in prey populations

• Increased biodiversity due to more available niches

• No impact on ecosystem stability

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