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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.

Morphology

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

what diseases and mode of sickness it causes and vector
Biola Reply
what is Biology
Sheku Reply
what is biology
Abel
biology is the study of life basically
Ajipha
bio means life and logy means study
Biola
what is biology?
William Reply
the study of living things
Joe
what's marketing
Mirabel Reply
what are hormones
Mirabel
what is meant by th word photosynthesis
MARTHA Reply
it is the process where by chloropherious plant manufacture their food with the presence of sunlight , chlorophyll and water etc.
Kosoe
it is the process by which green plant manufacture their food through sunlight and water ,chlorophyll.
Biola
what is biology
stallon Reply
is the study living things
Zhayma
and non living things
Zhayma
what is water circle?
Faith Reply
please i asks whether this biology is for university
Sky Reply
for secondary
stallon
Copulation means coming together of male and female in the present of sexual Intercourse.
LEKAN Reply
what are the adaptive features of nervous system
Ridhwan
Please what is ovulation
Adusei Reply
What is cell division?
Adusei
What is copulation?
Adusei
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qaisar
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qaisar
please tell me adaptive features of nervous system
Ridhwan
what is a metaborism
Beatrice Reply
this is a specialized part of the cell eg Nucleus
David Reply
what are adaptive features of nervous system
Ridhwan
what are the organelles?
Faith Reply
what is reproduction
mana Reply
reproduction is the process by which living organisms give rise to young ones of their own kind
Miriam
What is evolution
Wengelawit
the production of new forms of life over time as documented in the fossil record.
mana
hmm
Marvin
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Kevin Reply

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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