Unit 1: Ecosystems and Biodiversity

Answer: D — The correct answer is D) Predation, as the birds prey on the insect herbivores, demonstrating a predator-prey relationship. The other options are incorrect because mutualism (A) involves both species benefiting, commensalism (B) involves one species benefiting and the other being unaffected, and competition (C) involves both species competing for the same resources, which is not the case in this scenario.

Answer: A — The correct answer is A because the decline in the deer population will reduce the food source for predators that feed on deer, such as mountain lions, leading to a decline in their population. This is an example of a trophic cascade, where the change in one species' population has a ripple effect throughout the ecosystem. Option B is incorrect because the decline in deer population would not lead to an increase in predator population. Option C is incorrect because the decline in deer population would actually lead to an increase in plant population, not a decline. Option D is incorrect because the decline in deer population would not necessarily lead to a decrease in competition from other herbivores, and the increase in plant population would be due to the decline in deer grazing, not competition from other herbivores.

Answer: B — The correct answer, B, is the most likely effect because the decline of a specific tree species can lead to a decrease in biodiversity, as that species may play a unique role in the ecosystem. Additionally, the loss of that species can alter nutrient cycling and primary production, as trees are a key component of these processes. Option A is incorrect because the decline of a species will likely have some impact on the ecosystem. Option C is incorrect because the decline of a species will not typically increase biodiversity. Option D is incorrect because the decline of a species will likely have some impact on biodiversity.

Answer: C — The correct answer, C, is the most likely outcome because a decline in plant species diversity can have a ripple effect throughout the ecosystem, leading to a decline in the overall biodiversity. This is because plants are the primary producers of the ecosystem and provide habitat and food for many other species. The other options are incorrect because: A) the increase in deer population is due to the absence of their natural predators, so it is unlikely that their population will increase; B) the decline in plant species diversity will likely have a negative impact on the overall health of the ecosystem; and D) the overgrazing by deer will likely lead to a decline in the population of other herbivores, not an increase.

Answer: C — The correct answer, C, is the most likely explanation because many tree species have specific temperature tolerances, and an increase in temperature can cause heat stress, leading to decline or death. Option A is incorrect because there is no mention of human harvesting. Option B is possible, but not the most direct explanation. Option D is also possible, but the question suggests a more direct impact of temperature on the trees, rather than an indirect effect through disease.