Which of the following are single-celled micro-organisms that have both plant and animal characteristics?

The correct answer is protozoa, which are indeed single-celled microorganisms displaying both plant and animal characteristics. These microorganisms are part of the kingdom Protista and are characterized by their ability to move independently and feed in ways similar to animals, while also possessing some plant-like qualities such as the ability to produce energy through photosynthesis in certain species (though not all protozoa are photosynthetic).

This duality in characteristics allows protozoa to adapt to various environments and utilize different forms of nutrition, making them highly versatile. Understanding the unique traits of protozoa is essential in fields such as microbiology and ecology, as they play vital roles in ecosystems as both producers and consumers.

In contrast, viruses are not classified as living organisms because they cannot replicate without a host and do not possess cellular structures. Fungi are primarily multicellular organisms (with some exceptions like yeasts, which are single-celled), and they are not classified as plant or animal but rather form their own kingdom. Bacteria are single-celled prokaryotes and lack the complex structures found in both plant and animal cells, focusing instead on their own distinct classification.