Biological term structures that display characteristics of living organisms only within living cells?

Question: Biological term structures that display characteristics of living organisms only within living cells?

Viruses are microscopic structures that display characteristics of living organisms only within living cells. They consist of genetic material (DNA or RNA) enclosed in a protein coat, and sometimes have additional layers such as a lipid envelope. Viruses are not considered to be living organisms by most biologists, because they cannot perform the basic functions of life on their own, such as metabolism, growth, and reproduction. Instead, they rely on the host cell's machinery to carry out these processes.

Viruses can infect all types of living cells, from bacteria to plants to animals. They do this by attaching to specific receptors on the cell surface and injecting their genetic material into the cell. Once inside, the viral genes take over the cell's functions and direct it to produce more copies of the virus. The new viruses then exit the cell, either by bursting it open (lysis) or by budding off from the membrane (exocytosis). The infected cell may die or become dysfunctional as a result of the viral infection.

Viruses are responsible for many diseases in humans and other organisms, such as influenza, AIDS, chickenpox, measles, and COVID-19. Some viruses can also cause cancer by altering the host cell's DNA and making it grow uncontrollably. However, not all viruses are harmful. Some viruses can be beneficial for their hosts, such as bacteriophages that kill harmful bacteria, or endogenous retroviruses that integrate into the host genome and provide useful functions.

Viruses are fascinating structures that challenge our understanding of life and its origins. They are also important agents of evolution, as they can transfer genes between different species and create new genetic variations. By studying viruses and how they interact with living cells, we can learn more about the molecular basis of life and how to prevent and treat viral diseases.