Kaplan Nursing Entrance Practice Exam

How many domains classify all life on Earth?

1. Two

2. Three

3. Four

4. Five

The correct answer is: Three

The classification of all life on Earth is organized into three primary domains: Archaea, Bacteria, and Eukarya. This system was developed based on genetic and cellular structure differences and has been widely accepted in biological sciences. Archaea consists of prokaryotic organisms that often thrive in extreme environments. Bacteria also comprise prokaryotes that are more commonly found in everyday environments and are involved in various ecological processes. Eukarya encompasses all eukaryotic organisms, which have complex cells with a nucleus, including animals, plants, fungi, and protists. This three-domain system provides a better understanding of the fundamental differences in cellular organization and genetics among various life forms, which is why it is the widely accepted classification framework in modern biology.