The correct answer is a) domains. In biological classification, life on Earth is divided into three primary domains: Bacteria, Archaea, and Eukarya. Each of these domains represents a distinct group of organisms that share a common evolutionary history.
Bacteria are single-celled prokaryotic organisms that lack a nucleus. They are found in a vast array of environments and can be both beneficial and harmful to other life forms. Archaea, like bacteria, are also prokaryotic, but they have unique biochemical and genetic features that distinguish them from bacteria. Many archaea thrive in extreme environments, such as hot springs and salt lakes.
Eukarya, on the other hand, includes all organisms made up of eukaryotic cells. These cells have a nucleus and other membrane-bound organelles. This domain encompasses a wide variety of life forms, including animals, plants, fungi, and protists.
Understanding these three domains is fundamental to the study of biology, as they represent the major branches of life and highlight the diversity of living organisms on our planet.