Archaea and bacteria (eubacteria) are single-celled organisms that do not have a nucleus or organelles. Archaea have a distinct evolutionary history and biochemistry compared with bacteria.
Archaea - a domain of single-celled microorganisms. These microbes are prokaryotes. Archaea can survive in extreme and harsh environments like hot springs, salt lakes, marshlands, oceans, gut of ruminants and humans.
Bacteria - a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Eubacteria are ubiquitous and are found in soil, hot springs, radioactive waste water, Earth's crust, organic matter, bodies of plants and animals, etc.
Veganism is the practice of abstaining from the use of animal products, particularly in diet, and an associated rejection of the commodity status of animals. A follower of either the diet or the philosophy is known as a vegan.
Dietary vegans refrain from eating animal products, not only meat but also egg and dairy products and other animal-derived products. The term "ethical vegan" is often applied to those who extend the philosophy beyond diet into other areas of their lives. Environmental veganism refers to avoiding animal products on the premise that harvesting or industrial farming of animals is environmentally damaging and unsustainable.
The term vegan was coined in 1944 by Donald Watson when he co-founded the Vegan Society in England. At first this meant "non-dairy vegetarian" and later that one "should live without exploiting animals".