Are viruses alive? How do they compare with living cells?
Compare viruses with living organisms, including their structure and reproduction, and evaluate whether viruses meet the criteria for life (GSE SB4.c).
A Georgia Milestones Biology EOC answer on viruses: their structure (genetic material and protein coat), how they reproduce only inside a host cell, the characteristics of living things, and why viruses are generally not classified as alive.
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What this topic is asking
Standard SB4.c asks you to investigate viruses and compare them with living organisms, deciding whether they meet the criteria for life. For the Georgia Milestones Biology EOC you must know a virus's simple structure, that it can only reproduce inside a host cell, the characteristics of living things, and the reasoning for why viruses are generally not classified as alive. Items often ask for a comparison or for the criterion a virus fails.
What a virus is
So a virus is essentially genes in a protein shell. It is not built from a cell, which already sets it apart from every living organism.
How a virus reproduces
A virus cannot reproduce on its own. To make copies, it must infect a host cell: it attaches to the cell, inserts its genetic material, and takes over the host's machinery (ribosomes, enzymes, energy) to build new virus particles. The new viruses are released, often destroying the host cell, and go on to infect others. Because a virus depends entirely on a host for reproduction, it is sometimes called an obligate intracellular parasite.
The characteristics of living things
To judge whether a virus is alive, compare it with the characteristics of living things, which living cells all share:
- made of one or more cells,
- carry out metabolism (use energy, for example by cellular respiration),
- grow and develop,
- respond to the environment (stimuli),
- reproduce (independently), and
- maintain homeostasis.
Why viruses are generally not alive
This is an "evaluate" standard, so the EOC may ask you to argue the case: list the criteria, show which a virus meets (has genetic material, can evolve) and which it fails (not cellular, no metabolism, no independent reproduction), and conclude that it is generally not considered alive.
Try this
Q1. State the two main parts of a virus's structure. [2 points]
- Cue. Genetic material (DNA or RNA) and a protein coat (capsid); some also have an outer envelope.
Q2. State one characteristic of life that a virus has and one that it lacks. [2 points]
- Cue. Has: genetic material (and can evolve). Lacks: independent reproduction or metabolism (or being made of cells).
Exam-style practice questions
Practice questions written in the style of GaDOE exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Milestones (style)1 marksWhy are viruses generally not considered living things? (A) They contain no genetic material. (B) They cannot reproduce on their own without a host cell. (C) They are made of cells. (D) They carry out their own cellular respiration.Show worked answer →
A 1-point selected-response item on the criteria for life.
The correct answer is B. Viruses cannot reproduce by themselves; they must invade a host cell and use the host's machinery to make copies, so they fail a key criterion for life (independent reproduction and metabolism). A is wrong because viruses do contain genetic material (DNA or RNA), C is wrong because viruses are not made of cells, and D is wrong because viruses carry out no metabolism of their own. The inability to reproduce or carry out life processes independently is why viruses are usually classed as nonliving.
Milestones (style)2 marksCompare a virus with a typical cell by stating two characteristics of living things that a cell has but a virus lacks.Show worked answer →
A 2-point comparison item.
A living cell is made of one or more cells, carries out its own metabolism (such as cellular respiration to release energy), grows, responds to its environment, and reproduces independently. A virus lacks these: for example, (1) a virus is not made of a cell and has no cell membrane, cytoplasm, or organelles, and (2) a virus carries out no metabolism of its own and cannot reproduce without hijacking a host cell. Any two valid contrasts earn the marks, such as "not cellular" and "cannot reproduce or metabolize independently." Full points need two characteristics a cell has that a virus lacks.
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Sources & how we know this
- Biology Georgia Standards of Excellence (GSE) — Georgia Department of Education (2024)
- Georgia Milestones Biology EOC Assessment Guide — Georgia Department of Education (2024)