1. matrix
   1. farm
      1. cow, sheep, pig, goat
      2. chicken, turkey, duck, goose
   2. pets
      1. canary, parrot, budgie, dove
      2. dog, cat, Guinea pig, hamster
2. wild
   1. predators
      1. lion
      2. tiger
      3. panther
      4. leopard
   2. non-predators
      1. elephant
      2. giraffe
      3. gazelle
      4. hippopotamus
3. domestic
   1. farm
      1. cow
      2. sheep
      3. pig
      4. goat
   2. pets
      1. dog
      2. cat
      3. Guinea pig
      4. hamster