* Scale: Single-celled organisms are incredibly small. Even under a microscope, they can be difficult to see in detail. Therefore, if the focus is on larger organisms or structures, they might be omitted for simplicity or because they are too small to be represented effectively.
* Complexity: While single-celled organisms are fascinating, they are often more complex than they seem. Depicting all the intricate parts of a cell can be challenging and may not be necessary for the purpose of the illustration.
* Focus: The purpose of the image may be to highlight a specific biological process or system, which might not involve single-celled organisms.
* Audience: The intended audience may be unfamiliar with the intricacies of single-celled organisms. For example, a children's book about animals may not depict bacteria or protozoa.
Examples of where single-celled organisms are shown:
* Biology textbooks: Images of bacteria, protozoa, and algae are common in textbooks.
* Microscopy images: These images often show single-celled organisms in detail.
* Scientific articles: Research papers often include images of single-celled organisms.
* Art and design: Some artists and designers use single-celled organisms as inspiration for their work.
Ultimately, the decision of whether or not to show single-celled organisms depends on the context of the illustration.
