Which of the following organisms is part of the domain Eukarya?

The correct answer, Animalia, is part of the domain Eukarya because organisms classified within this domain possess eukaryotic cells, which are characterized by having a true nucleus and membrane-bound organelles. This group includes a diverse range of life forms, from single-celled organisms like protists to multicellular organisms such as plants, fungi, and animals.

In contrast, Bacteria and Monera are classified within the domain Prokarya, which comprises organisms that are characterized by their prokaryotic cells, meaning they lack a defined nucleus and other membrane-bound organelles. While prokaryotes include bacteria and archaea, they do not fall under the domain Eukarya. Prokaryotes are generally simpler in structure than eukaryotes.

The term "Prokaryote" itself represents a broad category of organisms that lack the complex cellular structures found in Eukarya, hence not fitting into the Eukarya domain. Recognizing these distinctions helps in understanding the classification of life forms and their cellular organization.