What is an animal? Very easy to answer. An animal is a member of the kingdom Animalia. An animal is not a Plant, a Fungus, a Protozoan, a Bacteria, and definately not a virus.
However, this definition includes some animals that don’t have nervous systems…and there is some evidence that things like sponges are unrelated to other animals. I think what the animal-definition people are trying to do is to get everyone to admit that humans are animals. Which they are. All mammals, all fish, all reptiles, all insects, all worms, all echinoderms, all coelenterates, all tardigrades, all rotifers, are animals. This is not a major issue…why do people need this defined before they’ll talk about animal rights? Pick up a biology textbook and find out for yourself what animals are.
Animal rights people agree that humans can kill plants, fungi, protozoans and bacteria morally. But why? What has a plant ever done to you that your life is more important? If we took the attitude that all life is sacred and that it is wrong to kill, we’d have to cut our throats…everything we eat is alive, or was alive. We had to kill animals or plants or bacteria to get it. I guess you could drink milk from cows…that’s not killing the cow. But the cow had to kill millions of blades of grass for your drink. That’s murder. You could be a fruititarian, and only eat fruits that plants offer freely…but there are probably lots and lots of insects and micro-organisms in that fruit that you kill when you eat them.
Now that we’ve defined “animals” lets get back to the morality of killing and eating them.