Which level of organization is present in both *Arachnoidiscus ehrenbergi* (a unicellular diatom) and the human stomach?

• A. Organ system
• B. Cell
• C. Tissue
• D. Organ

Answer: (B)

Verified step by step guidance

1. Understand the levels of biological organization: The levels of organization in biology range from the simplest (cell) to the most complex (organ system). These include cell, tissue, organ, and organ system.
2. Identify the organism types: *Arachnoidiscus ehrenbergi* is a unicellular diatom, meaning it consists of only one cell. The human stomach, on the other hand, is a part of a multicellular organism and is composed of tissues and cells.
3. Determine the common level of organization: Since *Arachnoidiscus ehrenbergi* is unicellular, its only level of organization is the cell. The human stomach, while more complex, is also composed of cells as its fundamental unit.
4. Compare the levels of organization: The human stomach includes higher levels of organization (tissue, organ, organ system), but the cell is the shared level of organization between the unicellular diatom and the human stomach.
5. Conclude that the correct answer is 'Cell': Both *Arachnoidiscus ehrenbergi* and the human stomach share the level of organization called 'Cell,' as it is the basic unit of life in all organisms.