SB 11.22.52
sattva-sangad rsin devan
rajasasura-manusan
tamasa bhuta-tiryaktvam
bhramito yati karmabhih
Translation:
Made to wander because of his fruitive work, the conditioned soul, by contact with the mode of goodness, takes birth among the sages or demigods. By contact with the mode of passion he becomes a demon or human being, and by association with the mode of ignorance he takes birth as a ghost or in the animal kingdom.
Purport:
The word tiryaktvam means “the status of an animal,” which includes all lower forms of life, such as beasts, birds, insects, fish and plants.