Final answer:
Life on Earth can be classified into three domains: Bacteria, Archaea, and Eukarya. Extremophiles, which thrive in extreme conditions, are often associated with Archaea. Eukarya, which include humans, oak trees, and mushrooms, are distinguished by cells with a nucleus.
Step-by-step explanation:
All known life on Earth can be classified into three domains: Bacteria, Archaea, and Eukarya. Organisms in the domain Bacteria and Archaea are prokaryotic, meaning their cells do not contain a nucleus, while Eukarya are made up of eukaryotic organisms that do have a nucleus. In terms of visual observation, the individual organisms that we can see with our eyes usually fall into the domain of Eukarya, which includes plants, animals, fungi, and protists. Extremophiles are organisms that thrive in extreme environmental conditions and are often found in the Archaea domain, although extremophiles are not the only members of this domain.
Archaea and Bacteria differ in their cell wall composition and genetics. They are similar in that neither has a nucleus. Phylogenetically, Archaea are more closely related to Eukarya than to Bacteria. The domain Eukarya is distinguished by the presence of a nucleus in the cells and contains four kingdoms: Protista, Fungi, Plantae, and Animalia. Examples of organisms in the domain Eukarya include humans (Homo sapiens), oak trees (Quercus species), and mushrooms (Basidiomycota species).