Lower lifeform
A lower lifeform, also identified as a low-level lifeform, primitive lifeform, lower species, lower animal, or inferior form of life, were terms used by many humanoids to describe non-sentient animals.

Biological 
According to Benjamin Sisko, "centuries ago, people on my world engaged in bloodsports, killing lower species for pleasure. A few cultures still do. But even they wouldn't consider hunting a sentient being. ()

After the Ferengi Grish was unable to lock on to Porthos  (aka "its language"), his partner Muk chided him for being a fool, as the dog was a lower lifeform, and "probably the 's next meal." Grish, however, did not share those feelings, as he pointed out size of Porthos' ears. ()

Unlike the Cheron natives' belief, Bele was surprised to learn that Humans (and/or Vulcans)  believed themselves to have descended from apes. Spock clarified Bele's comment, and explained that "the actual theory is that all lifeforms evolved from the lower levels to the more advanced stages." 

Later, upon the 's arrival at Cheron, the ship's sensors indicated that lower animals and vegetation were encroaching on the planet's uninhabited cities, and that no sapient lifeforms registered on the planet's surface. ()

When reading Seven of Nine's personal logs, Captain Kathryn Janeway read about one of Seven's dreams, where Seven described a raven, stating that "when it looks at me, I am paralyzed. I cannot move. It seems to know me, but I don't understand how that's possible. It's merely a bird, an inferior form of life, but the sight of it fills me with fear." ()

 Prejudicial 
The term was also as by beings as an outlet for their own prejudice, especially those that believed their species were superior to another. Such terms as subhuman species or subhuman race were examples that specifically used by Humans to describe, in extreme cases, Vulcans. (; )

The Sheliak considered Humans to be a lower lifeform, and according to Commander William T. Riker, "they would have no compunctions about exterminating the intruders" on Tau Cygna V. When Lieutenant Commander Data attempted to relay this information to colony leader Gosheven, he explained that the Sheliak "have little regard for Human life," and that they would not hesitate to eradicate the Human population there. Later, during face-to-face communication between Captain Jean-Luc Picard and the Sheliak director, the director offered to save the Federation time and stated that they "will eradicate the Human infestation." Picard responded by disputing the reference to them being an infestation, stating, "they are not vermin. They are citizens of the Federation. I will not permit this outrage!" ()

Doctor Gegen was wary about approaching the Humans aboard  and let his own prejudice get in the way of making proper first contact. According to Gegen, his species, the Voth, "have very poor relations with non-saurian races," and that "mammals in particular are considered to be a lower lifeform, but I must admit I've never gotten to know one before.''" ()
 

Lifeform classifications