Question

2.012) the gray wolf is a predator that keeps the herd numbers of elk and deer populations in check. with the disappearance of wolves, elk and deer populations exploded, which led to overgrazing of plants, especially in riparian zones. this led to increased erosion and polluted streams. the gray wolf is an example of _. a. a pioneer species b. mutualism c. predation d. a keystone species 2.013) in the savanna, an ostrich and gazelle feed next to each other and alert each other to danger. both species have different sight zones and can each spot potential danger in a different way. the ostrich and gazelle are an example of _. a. pioneer species b. mutualism c. predation d. keystone species 2.014) a bird building a nest in a tree is an example of _. a. commensalism b. mutualism c. predation d. parasitism 2.015) energy in ecosystems moves towards entropy, as all energy is eventually converted to _. a. biomass b. motion c. consumers d. heat

Explanation:

• For 2.012: A keystone species has a disproportionately large effect on its environment relative to its abundance. Gray wolves control elk and deer populations, and their disappearance has a cascading negative effect on the ecosystem, making them a keystone species.
• For 2.013: Mutualism is a symbiotic relationship where both species benefit. Ostriches and gazelles alert each other to danger, which is beneficial for both, so it's mutualism.
• For 2.014: Commensalism is a relationship where one organism benefits and the other is neither helped nor harmed. A bird building a nest in a tree benefits the bird, and the tree is generally unaffected, so it's commensalism.
• For 2.015: In ecosystems, according to the second - law of thermodynamics, energy moves towards entropy and is eventually converted to heat as it is used and dissipated in various metabolic processes.

Answer:

2.012) D. a keystone species
2.013) B. mutualism
2.014) A. commensalism
2.015) D. heat