What is the subject of a map

People keep spending additional units of a particular resource on a want until their marginal benefit is  decreasing withgreater thanless thannot affected by  their marginal cost.

The vegetation that thrives in the tundra is limited to a. mosses, barley, wheat, and corn. b. coniferous trees. c. dwarf shrubs, mosses, lichen, potatoes, and beans. d. mosses, lichen, algae, and dwarf shrubs.

What is the amount of organic matter in all living organisms in a habitat called?