If it turned out that a particular animal species, such as the starfish, lacked consciousness, then from an ethical perspective I believe it would belong in the same category as plants.
In some cases, we may want to refrain from killing such animals for ecological or environmental reasons, just as we may want to avoid destroying certain plants for the same reasons.
However, in principle, I do not see anything wrong with killing an animal for food if it has no more consciousness than a plant or a brain-dead person.
Continue with these questions:
- How do you know that plants cannot feel pain?
- What would you do if we discovered that plants can feel pain?
- Do plants move their leaves to follow the sun?
- Are there religions that believe plants have souls?
- How do you know whether other animals feel pain?
- Where does consciousness begin in the animal kingdom?
More answers: Vegan Ethics FAQ.