These animals are insentient, and do not experience events as good or bad, as Peter Singer puts it: "when a being is not capable of suffering, there is nothing to be taken into account." This group includes: non living things, plans, insects and molecules, thus all other animals arguably deserve moral consideration to some extent.
It isn't, however, this simple. There is a diverse range of opinions to consider; cartesians for example maintain that animals do not have moral status, due to their lack of conscious and thus they have no well-being to take into consideration. Another advocate of this thought was Peter Harrison who believes that "animals are not morally responsible for the acts the commit because while they may have behavioural dispositions, they go not have thoughts and beliefs about what is right and wrong, nor can they form a conscious intent." He concludes that despite animal face contortions or screams of pain (etcetera), our inference that they are experiencing displeasure is wrong, as pain behaviours can be experiences by non living entities as well as animals who merely act in such a way to survive in the environment. This appears to be flawed as faking injury is no stranger to the human mental capacity, and thus this shows no insight to the animals apparent mental states. Harrison's ideas that it is right for us to treat animals in a way that promotes human welfare was described as being a 'provocative and implausible thesis'; is it reasonable to assume that a shrieking dog is not a sign that the dog is experiencing pain? Harrison's cartesian view of animals moral status is captured by Malebranche's words: "They eat without pleasure, cry without pain, grow without knowing it; they desire nothing, fear nothing, and know nothing." Both Descartes and Harrison hold the opinion that animals are sentient automata, and were committed to the idea that animals lack any self-consciousness.