NSES Content Standard C 
Life Science: Organisms and their environments  
Grades K-4, page 129  

All animals depend on plants. Some animals eat plants for food. Other animals eat animals that eat the plants. 

Benchmark 5D The Living Environment: Interdependence of Life
Grades K-2, page 116
Animals eat plants or other animals for food and may also use plants (or even other animals) for shelter and nesting.

Benchmark 5E The Living Environment: Flow of Matter and Energy
Grades 3-5, page 119
Almost all kinds of animals' food can be traced back to plants.