A tree is a plant with an elongated stem, or trunk, supporting branches and leaves in most species. Trees tend to be long-lived, some reaching several thousand years old. Trees have been in existence for 370 million years.
A variety of plant species have independently evolved a woody trunk and branches to compete for sunlight. In more general sense, tall palms, tree ferns, bananas and bamboos are also trees. The roots branch out under the ground to anchor the tree and to extract moisture and nutrients from the soil. Above ground, the branches usually bear leaves, which capture light.
Trees reduce erosion and moderate the climate. Trees and forests provide a habitat for many species of animals and plants. Some trees provide edible fruit.
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.