Which of the following organisms does not exist as a single free-living cell?

Explanation

This question is asking which of the given organisms does not exist as a single free-living cell. The options are Amoeba, Euglena, Clamydomonas, and Volvox. The correct answer is Option D: Volvox. Volvox is a type of green algae that forms colonies of cells. Each colony can contain thousands of cells, which are connected to each other and function as a single organism. Therefore, it does not exist as a single free-living cell. In contrast, Amoeba is a single-celled organism that can move and engulf food particles. Euglena is also a single-celled organism that can move using a flagellum and has both plant-like and animal-like characteristics. Clamydomonas is a type of green algae that exists as a single free-living cell. Understanding the differences between single-celled and multi-cellular organisms is important in the study of biology. Single-celled organisms are capable of performing all necessary life functions on their own, whereas multi-cellular organisms have specialized cells and structures that allow them to perform specific functions. To learn more about this, please read the relevant sections of the recommended textbooks.