Identification

• Green plants use photosynthesis to transform light into energy stored in chemical bonds. Animals do not perform photosynthesis and thus rely on plants for the energy they need.
  
  

Features

• Animals also rely on plants for their essential nutrients. Elements like phosphorus and nitrogen are essential components of many biologically important molecules, but animals cannot obtain these nutrients from inorganic sources like rocks or air. Consequently, animals must obtain not only the energy but also the nutrients they need by eating plants.
  
  

Considerations

• Carnivores eat other animals, of course, and hence do not extract the nutrients and energy they need from plant sources. They still depend indirectly on plants, however, since the herbivores they eat could not survive without plants. Plants are the primary producers in most ecosystems. Organisms that eat plants are called primary consumers, while organisms that eat primary consumers are called secondary consumers.