Wolves were reintroduced to Yellowstone National Park in 1995. This keystone species restored the park’s ecosystem. What is the ecological value of a keystone species? A. They influence the survival of many other species in an ecosystem. B. They prevent the ecosystem from changing and growing. C. They protect land and water resources within the ecosystem. D. They decrease the number of unwanted species in an ecosystem.

Define the apical impulse and describe its normal location, size, and duration. which abnormal conditions may affect the location of the apical impulse? explain the mechanism producing normal first and second heart sounds. describe the effect of respiration on the heart sounds. describe the characteristics of the first heart sound and its intensity at the apex of the heart and at the base. describe the characteristics of the second heart sound and its intensity at the apex of the heart and at the base.