Organisms in their Environments

Buffelgrass is an invasive species of grass from Africa that outcompetes native Texas grasses for space and water. Which long-term change to a Texas grassland would most likely occur due to the introduction of buffelgrass?

• The population of native grasses will increase.

• The population of native grasses will decrease.

• Buffelgrass offspring will develop traits like those of native grasses.

• Buffelgrass offspring will develop traits like those of other invasive species.

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NGSS.MS-LS2-4

An environmental change drastically reduced the population of milkweed plants in an area. The milkweed plans provided that only source of food for a nearby population of monarch butterflies caterpillars. Which statement describes the most likely effect of this environmental change on this population of monarch butterflies.

• The number of monarch butterflies will decrease because their caterpillars will not have enough food.

• The number of monarch butterflies will stay the same because butterflies reproduce so rapidly their populations can withstand most food shortages.

• The number of monarch butterflies will stay the same because their caterpillars will begin consuming nectar from different types of flowers.

• The number of monarch butterflies will increase because their reproduction rate will increase to ensure some individuals survive.

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NGSS.MS-LS2-1

NGSS.MS-LS2-4

DDT is a pesticide that was once widely used to control agricultural pests and mosquitoes. However, this pesticide caused the eggshells of certain birds, including the brown pelican, to become fragile and thin. The adults would then accidentally crush the eggs while trying to incubate them. What happened to the brown pelican populations as a result of DDT used by humans?

• The populations increased much more slowly.

• The populations decreased as fewer eggs survived long enough to hatch.

• The populations remained stable over time.

• The populations increased as pelicans laid more eggs so that more offspring would survive.

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Researchers are studying lichens growing in a forest ecosystem. At the beginning of the study, the researchers identified twelve lichen species in the forest. Later, a forest fire happened in the study area. The researchers returned to the area and found only six lichen species. Which inference is the best supported from the researchers’ observations?

• Most lichen species are ineffected by forest fire.

• The biodiversity in a forest increases after a fire.

• Certain lichen species are better adapted to survive forest fires than others.

• Forest fires will permanently remove certain species from the ecosystem.

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NGSS.MS-LS2-4

The white-tailed ptarmigan lives at high elevations on mountains that receive a lot of snow in the winter. During the summer, the ptarmigans’ feathers are mottled brown. The birds lose the brown feathers and grow a new set of white feathers during the winter. Scientists are concerned that rising global temperatures will affect the white-tailed ptarmigan. If global climate change leads to the elimination of snow in the habitat of white-tailed ptarmigans, which adaptations is most likely to occur over many generations?

• Birds with white feathers in areas without winter snow will be easier for predators to find. Over time this could lead to white-tailed ptarmigans that have brown feathers throughout the year.

• Birds with brown feathers in areas without winter snow will be easier for predators to find. Over time this could lead to white-tailed ptarmigans that have white feathers throughout the year.

• Birds with white feathers will be easier to see on the ground in the summer. Over time this could lead to white-tailed ptarmigans that have white feathers throughout the year.

• Birds with brown feathers will be easier to see on the ground in the winter. Over time this could lead to white-tailed ptarmigans that have have brown feathers throughout the year.

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To fight a bacterial infection, a patient was given an antibiotic to take for 10 days. After the patient finished taking the antibiotics as directed, almost all the bacteria were killed. After another 10 days, the patient was sick again with the same type of infection. What most likely happened?

• A few bacteria survived the antibiotics and stopped reproducing.

• The patient's high fever inactivated the antibiotic, allowing the surviving bacteria to grow rapidly.

• The antibiotic slowed the life cycle of the bateria.

• Some of the bacteria were resistant to the antibiotic, and they reproduced.

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NGSS.MS-LS4-4