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Evolution of viruses

Although biologists have accumulated a significant amount of knowledge about how present-day viruses evolve, much less is known about how viruses originated in the first place. When exploring the evolutionary history of most organisms, scientists can look at fossil records and similar historic evidence. However, viruses do not fossilize, so researchers must conjecture by investigating how today’s viruses evolve and by using biochemical and genetic information to create speculative virus histories.

While most findings agree that viruses don’t have a single common ancestor, scholars have yet to find a single hypothesis about virus origins that is fully accepted in the field. One such hypothesis, called devolution or the regressive hypothesis, proposes to explain the origin of viruses by suggesting that viruses evolved from free-living cells. However, many components of how this process might have occurred are a mystery. A second hypothesis (called escapist or the progressive hypothesis) accounts for viruses having either an RNA or a DNA genome and suggests that viruses originated from RNA and DNA molecules that escaped from a host cell. A third hypothesis posits a system of self-replication similar to that of other self-replicating molecules, likely evolving alongside the cells they rely on as hosts; studies of some plant pathogens support this hypothesis.

As technology advances, scientists may develop and refine further hypotheses to explain the origin of viruses. The emerging field called virus molecular systematics attempts to do just that through comparisons of sequenced genetic material. These researchers hope to one day better understand the origin of viruses, a discovery that could lead to advances in the treatments for the ailments they produce.

Viral morphology

Viruses are acellular    , meaning they are biological entities that do not have a cellular structure. They therefore lack most of the components of cells, such as organelles, ribosomes, and the plasma membrane. A virion consists of a nucleic acid core, an outer protein coating or capsid, and sometimes an outer envelope    made of protein and phospholipid membranes derived from the host cell. Viruses may also contain additional proteins, such as enzymes. The most obvious difference between members of viral families is their morphology, which is quite diverse. An interesting feature of viral complexity is that the complexity of the host does not correlate with the complexity of the virion. Some of the most complex virion structures are observed in bacteriophages, viruses that infect the simplest living organisms, bacteria.


Viruses come in many shapes and sizes, but these are consistent and distinct for each viral family. All virions have a nucleic acid genome covered by a protective layer of proteins, called a capsid    . The capsid is made up of protein subunits called capsomeres . Some viral capsids are simple polyhedral “spheres,” whereas others are quite complex in structure.

Questions & Answers

hi I'm asking a question about HIV infection, can HIV infection transmitted from Mother to unbron child? please help me I So confused.
Khushboy Reply
what is the difference between primary and secondary active transport in detail? I didn't understand the steps in the textbook specifically
Fathima Reply
you are a doctor?
what is the meaning of connective tissue?
Mohammed Reply
what are the characteristics of living things
Owolo Reply
what's the meaning of connective tissue?
Reproduction, adaptation, interaction, movement, growth, respiration, made of cells, responsive to environment (homeostasis), metabolic action (consumption of food converted into energy)
state two most important factors that favour exponential growth of population of a gazelle in a pack
Eliza Reply
what are the two types of electron microscope
Sharlom Reply
light microscope and early microscope
Enzymes are biological catalyst which alter any reaction and protein in nature
Nkoue Reply
Your welcome sir
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What is translation and transcription
Transcription is making RNA from DNA. Translation is going from RNA to proteins.
full meaning of RNA and DNA
Nkoue what homeostits means?
Mohammed khalfan, In biology, homeostasis is the state of steady internal, physical, and chemical conditions maintained by living systems.[1] This dynamic state of equilibrium is the condition of optimal functioning for the organism and includes many variables, such as body temperature and fluid bal
what is the definition of enzymes
Royd Reply
enzymes are biological catalyst that speed up chemical reaction.
What are enzymes?
Enzymes are made of proteins and lower the energy of activation. In other words, they bring things together which helps to lower the amount of energy for a reaction to go forward.
they are catalyses that speeds up chemical reaction.... e.g they break down the food we consume.
These are catalyst that speeds up the chemical reaction.
What is connective tissue?
what homeostits means ?
what is a spirogyra
Talabi Reply
Spirogyra is a filamentous chlorophyte green algae of the order Zygnematales. It is named for the helical or spiral arrangement of the chloroplasts. That is characteristic of the genus. It is commonly found in freshwater habitats. And there are more than 400 species of Spirogyra in the world.
what is the mean of biology
Bello Reply
what is cell
A cell is the smallest living unit.
Hi I'm new in this group can someone please help with the list features shared by plants and charopytes that are not shared with most other eukaryotes
iz a basic units of a living thing?
what is eutrophication
Chinaza Reply
hi.. I'm asking a question about HIV infection.... Can HIV infection transmitted from Mother to unbron child?
Eutrophication is an enrichment of water by nutrient salts that causes structural changes to the ecosystem such as: increased production of algae and aquatic plants, depletion of fish species, general deterioration of water quality and other effects that reduce and preclude use.
Show well labeled diagram of female reproductive organs
Lanlege Reply
phenotype is your big head
Amagiya Reply
The phenotype is the physical appearance or things you can see. Or the traits expressed by ones DNA.
phenotypes are appearance that can be seen and touched
example of phenotype
what is a dichotomous key
Moses Reply
explain the role of
Dichotomous key : Is the key that is use to classify or group an organism base on their common features
an amoeba is what kind of cellular organism?
Mercy Reply
It is a protizoa with bilayer membrane bound organelles. Therefore it is eukaryotic.
what is amoeba
amoeba is a unicellular organisms. Therefore it is made u of only one call.
what is phenotype
amoeba is a unicellular organism with one cell

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