1. Protozoa are single celled, eukaryotic organisms that exhibit animal-like behaviour.
- Viruses consists only of genetic material and a protein coat, and they are known to cause a wide variety of diseases such as AIDS.
- Fungi have characteristics similar to plants, but they do not have root systems like plants do and they also do not rely on chlorophyll to photosynthesize.
- Bacteria make up this category.
- Rickettsiae is a genus of bacteria that are intracellular parasites.