Exercise 12.5
You find an unlabelled slide of a single-celled organism that has a well-defined nucleus and multiple cilia. Which group would it most likely belong to? Give reasons.
Not cross-checked
NCERT prints no numerical answer for this exercise, so this working has not been cross-checked against the book.
Kingdom Protista — most likely a ciliate such as Paramecium.
A well-defined nucleus means a eukaryote, so it cannot be Monera — bacteria and cyanobacteria have only a primitive nucleus with no bounding membrane.
Single-celled rules out Plantae and Animalia, both of which are multicellular by definition in the five kingdom system.
It also rules out Fungi in practice. Fungi are mostly multicellular, and the one-celled exception, yeast, is admitted only because its cell wall is made of chitin. A ciliated swimmer with no chitin wall does not qualify.
What is left fits exactly: Protista is defined as single-celled eukaryotes with no cell wall, or with a cellulose wall — microscopic, highly diverse, living in water or moist places.
The cilia confirm it. They are locomotory structures for a free-swimming, water-dwelling microorganism, and Paramecium is one of the protists the chapter illustrates in Fig. 12.7.
To be sure, check two more things: whether a cell wall is present and what it is made of, and the mode of nutrition (protists may be autotrophic or heterotrophic — either is consistent).
