What is measured in terms of energy capture per unit area per year in an ecosystem?

Productivity is the correct choice as it refers to the rate at which energy is captured and converted into biomass in an ecosystem, typically expressed as energy per unit area per year. This concept is fundamental in ecology as it quantifies how effectively an ecosystem converts sunlight or other forms of energy into organic matter, which is crucial for understanding the energy flow within ecosystems.

In terrestrial ecosystems, primary productivity is primarily driven by plants through photosynthesis, while in aquatic ecosystems, both phytoplankton and macrophytes contribute to productivity. Measuring productivity allows scientists to assess the health and efficiency of ecosystems, as well as their capacity to support diverse forms of life.

While biomass refers to the total mass of organisms in a given area, it does not measure the rate of energy capture. Succession refers to the process of ecological change and development over time in an ecosystem, and habitat diversity describes the variety of different habitats within an ecosystem. Neither of these concepts directly relates to the measurement of energy capture, making productivity the most appropriate answer to the question.