No population can grow indefinitely. The ultimate size of any population is limited by __________.

• A. its r
• B. its birth rate
• C. its death rate
• D. reproductive isolation
• E. the carrying capacity of its environment

Answer: (E)

Verified step by step guidance

1. Understand the concept of carrying capacity: Carrying capacity is the maximum number of individuals of a particular species that an environment can support sustainably over time, given the food, habitat, water, and other necessities available in the environment.
2. Recognize that population growth is influenced by various factors: These include birth rates, death rates, immigration, and emigration. However, these factors are ultimately constrained by the carrying capacity of the environment.
3. Identify the role of 'r' in population growth: The intrinsic rate of increase (r) is a measure of how fast a population can grow when no resources are limiting. However, in real-world scenarios, resources are limited, and thus, the carrying capacity becomes the limiting factor.
4. Differentiate between short-term and long-term population dynamics: In the short term, populations may exceed their carrying capacity, leading to resource depletion. In the long term, populations tend to stabilize around the carrying capacity due to resource limitations.
5. Conclude that the ultimate size of any population is limited by the carrying capacity of its environment, as it determines the maximum sustainable population size given the available resources.