A particular environmental change causes the deaths of 25 individuals in a herd of 100 wild horses, and it kills 50 individuals in a herd of 200 horses. In this case, the growth of a wild horse population is most likely limited by __________. (Assume that the two herds are found in territories of equal size.)

• A. a density-dependent factor
• B. food supply
• C. a predator
• D. the presence of another species that uses the same food resource
• E. a density-independent factor

Answer: (E)

Verified step by step guidance

1. Understand the concept of density-dependent and density-independent factors. Density-dependent factors are those that affect the population based on its size, such as competition, predation, and disease. Density-independent factors affect the population regardless of its size, such as natural disasters or environmental changes.
2. Analyze the problem: The environmental change causes the deaths of 25 individuals in a herd of 100 horses and 50 individuals in a herd of 200 horses. Notice that the proportion of deaths is the same in both herds (25% of each herd).
3. Consider the options provided: Density-dependent factors would typically result in different proportions of deaths based on herd size, as larger populations might experience more competition or disease spread. However, the problem states equal proportions of deaths in both herds.
4. Evaluate the impact of density-independent factors: Since the environmental change affects both herds equally in terms of percentage, it suggests that the factor is density-independent, as it impacts the population regardless of its size.
5. Conclude that the growth of the wild horse population is most likely limited by a density-independent factor, as the environmental change affects both herds equally in proportion, not based on their size.