animals should not be killed for any reason

How do you know for sure whether or not Animals feel pain? Whether animals can feel pain has been a theory, not a proven fact. Also, where are your sources for your arguments? Types of PainPain can be considered to have two components: Physical hurt or discomfort caused by injury or disease and Emotional suffering. Most people would agree that animals are capable of feeling pain according to the first definition. But it is less clear whether they also feel emotional pain. This is a theory, not a fact. Sensing damageOne of the functions of pain is to warn against damage and to act as an alarm system so that action can be taken to avoid or minimize injury. This usually takes the form of a withdrawal reflex. In vertebrates, nociceptive information is collated and augmented in the brain and signals are relayed down the nervous system to alter the intensity of pain. All vertebrates possess the primitive areas of the brain to process nociceptive information, namely the medulla, and the thalamus However, one area of great importance for pain perception in humans is the cortex and its relative size decreases as we descend the evolutionary tree. For instance, in relative terms, the cortex gets smaller going from humans, through primates, mammals, birds, reptiles, amphibian and finally to fish, which possess only a rudimentary cortex. BehaviourOther animals show reflex responses similar to our own. For example, when we accidentally touch a hot iron we respond almost immediately by retracting our hand. There is a lag period following this when no adverse sensations are felt but, if left untreated, the burn begins to throb and we alter our behaviour to guard the affected area. Other animals respond to painful damage in a similar way. Their responses comprise several behavioural and physiological changes: they eat less food, their normal behaviour is disrupted, their social behaviour is suppressed and they may adopt unusual behaviour patterns (typically, highly repetitive or stereotyped behaviours, such as rocking to and fro), they may emit characteristic distress calls, and they experience respiratory and cardiovascular changes, as well as inflammation and release of stress hormones. As these responses are complex and coordinated, it is likely that the brain is involved and they are more than just simple reflexes. Although comparatively simple, fish have recently been shown to possess sensory neurons that are sensitive to damaging stimuli and are physiologically identical to human nociceptors. Fish show several responses to a painful event: they adopt guarding behaviours, become unresponsive to external stimuli and their respiration increases. These responses disappear when the fish are given morphine – evidence that they are, mechanistically at least, directly analogous to pain responses in more complex animals. Emotional painAnother theory. Humans can certainly feel pain without physical damage – after the loss of a loved one, or the break-up of a relationship, for example. Some scientists suggest that only primates and humans can feel emotional pain, as they are the only animals that have a neocortex – the ‘thinking area’ of the cortex found only in mammals. However, research has provided evidence that monkeys, dogs, cats and birds can show signs of emotional pain and display behaviours associated with depression during painful experience, i. e. . lack of motivation, lethargy, anorexia, unresponsiveness to other animals. Although modern philosophers have debated this issue, we simply do not know whether animals experience emotional pain. In his essay ‘What is it like to be a bat? ’, Thomas Nagel concluded that unless we can get inside the head of an animal and actually be it, we will never know exactly how that animal feels. An important issue in animal pain is empathy, and many arguments about what animals feel have can only be based on the human experience and, therefore, may be tainted with anthropomorphism. Another argument against animals experiencing pain is the question of whether animals are conscious. Scientists have argued that no animals, except primates, are capable of feeling pain, as they are not conscious. In essence, consciousness is a sense of an awareness of how things affect me and how something feels. Whether animals are conscious, or possess some degree of consciousness, has been endlessly debated, but consciousness is such a subjective experience it is hard to define and to assess. Fish can certainly learn complicated tasks, remember approximately 40 individuals, and measure their size relative to an opponent’s to decide whether to fight them. Therefore, at the very least they must have a sense of how big they are. Higher vertebrates show even more significant signs of consciousness. Some Scientists have suggested that animals may be conscious but that this is not as developed as human consciousness. Many argue, however, that consciousness is fundamentally dependent on language, something no other animal has yet been convincingly shown to possess. In contrast, Peter Singer, a bio ethicist who has championed animal rights for many years, suggests that consciousness is not even the key issue: just because animals have smaller brains, or are ‘less conscious’ than humans, this does not mean that they are not capable of feeling pain. After all, says Singer, we do not assume that newborn infants, people suffering from neurotic brain diseases or people with learning disabilities experience less pain than we would. In practice, welfare scientists, who assess animal well being in various contexts including intensive farming, try to be unbiased and objective when monitoring behavioural and physiological responses to potentially painful events. If an animal shows the same kind of adverse reactions as humans after a painful stimulus, it is assumed that the stimulus is also painful to the animal. Inevitably, however, all welfare science on pain is essentially a interpretation based on indirect measurements. Weighing the evidenceIn conclusion, it is currently impossible to prove whether animals are capable of emotional pain, but it is equally impossible to disprove it. The conclusion is drawn; it is impossible to know for sure. The whole idea of animals being slaughtered is to show a sense of compassion of animals, when we certainly don't even know. Sources: . http://www.ncbi.nlm.nih.gov...http://en.wikipedia.org...http://www.grandin.com...http://www.ucmp.berkeley.edu...Also, a question for Pro, whenever we kill a fly, mosquito, Etc; do they feel pain? They are animals also, right?