Physiological population density differs from crude population density in that physiological density:

• A. is calculated as the number of people per unit area of arable (farmable) land
• B. is calculated as the number of people per total land area, regardless of land usability
• C. refers to the number of births per 1,000 individuals in a population per year
• D. measures the number of organisms per unit volume of water

Answer: (A)

Verified step by step guidance

1. Understand the key terms: 'Physiological population density' and 'Crude population density'. Physiological density refers to the number of people per unit area of arable (farmable) land, while crude density refers to the number of people per total land area, regardless of land usability.
2. Eliminate the incorrect options by analyzing their definitions: The option 'refers to the number of births per 1,000 individuals in a population per year' describes birth rate, not population density. Similarly, 'measures the number of organisms per unit volume of water' pertains to aquatic population density, not human population density.
3. Focus on the distinction between arable land and total land area: Physiological density specifically considers arable land, which is land suitable for farming, while crude density does not differentiate between usable and non-usable land.
4. Relate the concept to its practical implications: Physiological density provides insight into the pressure placed on productive land by the population, which is crucial for understanding agricultural sustainability and resource management.
5. Conclude by identifying the correct definition: The correct answer is that physiological population density is calculated as the number of people per unit area of arable (farmable) land.