Eukariotic cells have nuclei, while prokaryotic cells do not.
Much like a cell, a virus is able to grow and reproduce in large numbers
A virus is a microscopic nonliving parasite that only reproduces inside the cells of living hosts. Like cells, viruses have the ability to grow and reproduce within the host cell. When a virus infects a host cell, it injects its genetic material into the cell and forces the host cell to produce thousands of similar copies of the original virus.
Answer:
<h3>Biologists study humans, plants, animals, and the environments in which they live. They may conduct their studies--human medical research, plant research, animal research, environmental system research--at the cellular level or the ecosystem level or anywhere in between.</h3>