Metabolic Theory of Evolution Responses
1. Living “things” must maintain homeostasis
Are viruses made up of cells?
Are viruses able to monitor or create change in their internal environment?
No, Viruses are not cells since they are not capable of self-replication and are not considered “living.” The capacity of viruses to replicate their genes, synthesize all of their proteins, or replicate on their own is limited; as a result, they must parasitize the cells of other life forms to do so2. Viruses infiltrate cells and subsequently take over the cell’s mechanism to promote their reproduction. The newly generated viruses are later released from the host cell and spread throughout the host body. Maintaining homeostasis, which is balanced inside the body, is essential for all living organisms. Our bodies produce sweat to keep us cool. Throughout the day, billions of changes are made to keep our body temperature and chemicals in our body regulated within their stable limits. Because viruses lack cellular organs and bodily fluids, they are unable to govern their internal environment, and as a result, they cannot manage their homeostasis1.
2. Living “things” have different levels of organization.
Do viruses have different levels of organization?
In contrast to living organisms, viruses lack the vast majority of the internal structure and machinery that distinguishes them, including the biosynthetic machinery required for reproduction. For a virus to reproduce, it must first infect a cell that is suited for replication.” On the other hand, the virus has degrees of organization in that it has genes comprised of nucleic acids and a protein coat known as a capsid built of smaller protein units known as capsomeres.
3. Living “things” reproduce
Do viruses replicate or reproduce?
Yes, viruses do replicate, but they can’t multiply on their own; instead, they must rely on the genome synthesis pathways of their host cell to reproduce successfully7. This usually happens due to the virus inserting its genetic material into host cells, capturing and utilizing the host proteins to generate viral particles that self-assemble and eventually cause the cell to burst due to the vast amount of new viral particles synthesized during this process2.
4. Living “things” grow
Do viruses grow in size or complexity?
Because of their basic structure, viruses cannot move or multiply on their own without the assistance of a susceptible host cell. However, once a virus has found a host, it can grow and spread quickly. In order to infiltrate the host, viruses have evolved receptors on their surfaces that are identical to those of their ideal target cell, allowing the virus to enter the cell and hijack the host’s cellular machinery and multiply its genetic material and proteins. This tiny machinery has prospered and grown in complexity alongside their host species3.
5. Living “things” use energy
Do viruses use energy?
No, because to survive, viruses must take energy from the cells they infect. Because viruses are too little and straightforward to manufacture, store, or utilize their power, they steal it from their infected cells. Viral replication necessitates the expenditure of energy only when the virus replicates itself, and while the virus is outside of a cell, it requires no energy at all. In contrast to bacteria, viruses cannot create or store energy in the form of adenosine triphosphate (ATP) and must instead get energy and all other metabolic processes from the host cell1.
6. Living “things” respond to stimuli
Do viruses respond to external stimuli?
No, Viruses do not react to external stimuli; they do not grow, move toward, or away from any external stimuli, and they do not have any specific receptor to receive external stimuli.
7. Living “things” adapt to their environment
Do viruses adapt to their environment?
Yes, like any living creature, a virus changes over time can adapt to its environment. On the other hand, Viruses are unable to use their genetic material on their own, and they need the presence of a living host cell required to function and multiply; else, they act as if they are lifeless. Although the virus and its host have evolved separately throughout time, both have remained well suited to each other4.
In the bible, God says:
For you formed my inward parts; you knitted me together in my mother’s womb. I praise you, for I am fearfully and wonderfully made. Wonderful are your works; my soul knows it very well. My frame was not hidden from you when I was being made in secret, intricately woven in the depths of the earth. Your eyes saw my unformed substance; in your book were written, the days that were formed for me, when as yet there was none of them (Psalm 139:13-16)5.
4. Simmonds P, Aiewsakun P, and Katzourakis. Prisoners of war — host adaptation and its constraints on virus evolution. Nat Rev Microbiol. 2019;17, 321–328. https://doi.org/10.1038/s41579-018-0120-2
5. Engleberg, N. C., Dirita V., Dermoby, T. S. (2014). Schaechter’s mechanisms of microbial disease – with access (5th ed.). Philadelphia, PA: Lippincott, Williams, & Wilkins.
6. Keith D, Farnsworth. An organizational systems-biology view of viruses explains why they are not alive. Biosystems, Volume 200. 2021;104324.https://doi.org/10.1016/j.biosystems.2020.104324.
7. Gomez-Marquez J. What Is Life? Are Viruses Living Entities? 2020;2020080661. doi:10.20944/preprints202008.0661.v1.
8. Joshua M. Moritz. Are Viruses Evil? Theology and Science. 2020;18:4,564-578. doi.10.1080/14746700.2020.1825191
9. The Holy Bible. King James Version, Cambridge. 2020.
10. McClintock, Thomas. 2021. Module 1:Liberty University Video: General Characteristics and Properties of Viruses. https://canvas.liberty.edu/courses/192468/pages/watch-general-characteristics-and-properties-of-viruses?module_item_id=23064345
Are Viruses Alive?
The debate on whether viruses are living or non-living has existed in scientific research for a long time. This answer to this debate is based on the definition of the state of being alive or life. In most instances, scientists describe life based on the ability to adapt to the environment, respond to stimuli, use energy, grow, reproduce, have different levels of organization, and maintain homeostasis.1 The argument of whether viruses are alive is based on comparing the properties of viruses and these seven major characteristics of living things.
Homeostasis is an important property of living things as it enables them to maintain the stable chemical, physical, and internal conditions.3 Viruses do not have cells; therefore, they cannot change or monitor changes in their internal environment; this aspect disqualifies viruses from being living things.
Viruses lack different organization levels, including organs, organ systems, tissues, and cells. Its genetic material is protected by a protein coat.3 Viruses also lack cell membranes and organelles that are present in all living things. Therefore, the organization levels differentiates viruses from living things.
Although they do not have the necessary tools such as nuclei and organelles to reproduce like living things, they depend on their hosts to replicate. They achieve this by inserting their genetic material into the host’s cell. As a result, the cell replicates the virus DNA, thus aiding in its reproduction. In Genesis 1:28, God tells all living things to multiply and be fruitful, thus indicating that living things should reproduce.2 Therefore, since viruses have their way of replicating, they meet God’s perspective of living things.
Unlike living things that grow, viruses do not grow. Instead, they influence the host cell to create new viruses outside it. While outside the cell, the virus does not increase in size or complexity. Other living things, such as animals, grow in size and complexity. Therefore, this property also distinguishes viruses from living things.
Viruses are too simple and small to use or collect their energy. Therefore, they steal it from their host cell. They use energy only when making their copies and are active only when in contact with the host cells. Living things make and use their energy through their mitochondria, such as plants and animals. However, some bacteria depend on their hosts for energy; therefore, this property does not completely distinguish viruses from living things.
Although they do not respond to stimuli, viruses may initiate this action to several biological stimuli, including proteases, redox, and pH.3 This response allows for modified intracellular trafficking and more stability. This aspect of viruses makes them qualify to be living things.
Viruses adapt to the environment, which is similar to that of living things. They achieve this adaptation through continuously changing into diverse phases using the host cell.4 Once changed, viruses proceed to infect other cells, thus replicating. A virus interacts with the cell it has infected.
By comparing viruses and living things based on the seven main characteristics of living things, it is unclear whether viruses are alive. Although they qualify in some of the characteristics, such as responding to stimuli and adapting to the environment, they still fail in aspects such as possessing levels of organization and homeostasis. Therefore, based on the outcomes of this scientific criterion of determining whether viruses are alive or not, the answer is unclear as it depicts the characteristics of both living and non-living things.
1. Arizona State University. Are viruses alive? Arizona State University website. https://askabiologist.asu.edu/questions/are-viruses-alive
2. The Holy Bible. Genesis 1: 28
3. Brun, M.J., Gomez, E.J. and Suh, J. Stimulus-responsive viral vectors for controlled delivery of therapeutics. Journal of Controlled Release, 2017; 267;80-89. doi:10.1016/j.jconrel.2017.08.021
4. Koonin, E.V. and Starokadomskyy, P., 2016. Are viruses alive? The replicator paradigm sheds decisive light on an old but misguided question. Studies in history and philosophy of science part C: Studies in history and philosophy of biological and biomedical sciences, 2016; 59; 125-134. doi:10.1016/j.shpsc.2016.02.016