18. Answer in detail I

 

a. The study of bacteria is called pathologybacteriology. Bacteria are microscopic, single-celled, prokaryotic organisms because they do not have a true nucleus and other membrane-bound cell organelleshave a true nucleus and other membrane-bound cell organelles. Bacteria are classified under the kingdom called ProtistaMonera. The size of bacteria ranges from 1μm to 5μm.

 

b. The lamellacell wall  is the outer layer of a bacterium. A nucleoid without a nuclear membrane represents nuclear material. In the cytoplasm, there is an extra chromosomal DNA called plasmaplasmid. 70S ribosomes are responsible for protein synthesislipid synthesis. Other cell organelles, such as mitochondria, Golgi bodies, and endoplasmic reticulum, are absent. Flagella helps in locomotion.