Final answer:
Viruses are microscopic infectious agents with genetic material and a protein coat, requiring a host cell to replicate. They are challenging to study in a lab due to their dependence on host cells, their small size, and the need for special containment facilities. They have characteristics of life, such as genetic material and evolution, but are not considered living organisms.
Step-by-step explanation:
A virus is a microscopic infectious agent that can only replicate inside the cells of a host organism. Viruses consist of two main components: genetic material (either DNA or RNA) and a protein coat called a capsid that protects the genetic material. Some viruses also have an outer envelope composed of lipids.
Unlike living organisms, viruses are not made of cells, do not possess a cellular structure, and do not metabolize or reproduce independently. They need a host cell to create new virus particles (virions), utilizing the host's cellular machinery to replicate their genetic material and produce proteins for new virions. A phage is a type of virus that infects and replicates within bacteria.
Studying viruses in a lab setting can be complex because viruses cannot be cultured in the same way as bacteria or other microorganisms. They require a living host cell for replication, making them difficult to observe and analyze outside of a living organism. Furthermore, their small size and high specificity for certain hosts add to the challenge. Virologists must use specialized techniques and containment facilities to safely study viruses and their life cycles.
Even though viruses are not considered alive, they exhibit two key characteristics of life: they contain genetic material and have the capacity to evolve due to selective pressures. However, their lack of other life processes classifies them as intricate biological entities distinct from truly living organisms.