ABSTRACT
Various types of heterotrophs were discussed as biotic factors of the environment in Chapter 11. In this context, we looked at the interactions between heterotrophs and other organisms, and our interest was in categorizing these interactions and distinguishing them by type, rather than in examining the heterotrophs themselves. In this chapter, we shift our frame of reference to the heterotrophic organisms, looking at these organisms directly rather than as special kinds of biotic factors. This results in two related but distinct discussions. In Heterotrophs as Factors Affecting Crop Plants, we focus on heterotrophs as factors of the environment but give attention to the organisms involved and the particular effects they have on crop plants. In Animals as Resources in Agricultural Production, we discuss animals as organisms from which humans derive food and which, like crop plants, confront an environment made up of separate factors.
