IB Biology Topic A2.3.6 Rapid Evolution in Viruses Revision Notes (HL)

IB Biology Topic A2.3.6 Rapid Evolution in Viruses Revision Notes (HL) | RevisionDojo

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Why Do Viruses Evolve So Quickly?

Viruses evolve extraordinarily fast, accumulating genetic changes even within a single infection.
Their short generation times, high mutation rates, and strong selective pressures drive rapid adaptation, allowing them to evade immune systems, resist drugs, and cross species barriers.
Short Generation Times:
Viruses replicate within minutes to hours, compared to decades for multicellular organisms.
Each replication cycle offers new opportunities for mutations to arise and spread.

Tip

Fast replication = more replication events = faster evolution.

High Mutation Rates:
Mutations introduce the variation necessary for evolution.
RNA viruses mutate faster than DNA viruses because of differences in replication enzymes:

Virus Type	Replication Enzyme	Proofreading?	Mutation Rate
DNA viruses	DNA polymerase	Yes	Low
RNA viruses	RNA polymerase / reverse transcriptase	No	High

Note

Without proofreading, RNA viruses accumulate frequent errors, generating genetically diverse populations within a single host.

Hint

High mutation rates are risky for stability but beneficial for adaptability.

Intense Natural Selection:
Viruses face constant selective pressures from their hosts:
1. Immune defenses (e.g., antibodies targeting viral antigens)
2. Antiviral drugs
3. Transmission barriers between hosts
Variants with mutations that help them evade immunity or resist drugs survive and proliferate.

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Tip

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Lorem ipsum dolor sit amet, consectetur adipiscing elit.
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Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
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Why Do Viruses Evolve So Quickly?

Viruses evolve extraordinarily fast, accumulating genetic changes even within a single infection.
Their short generation times, high mutation rates, and strong selective pressures drive rapid adaptation, allowing them to evade immune systems, resist drugs, and cross species barriers.
Short Generation Times:
Viruses replicate within minutes to hours, compared to decades for multicellular organisms.
Each replication cycle offers new opportunities for mutations to arise and spread.

Tip

Fast replication = more replication events = faster evolution.

High Mutation Rates:
Mutations introduce the variation necessary for evolution.
RNA viruses mutate faster than DNA viruses because of differences in replication enzymes:

Virus Type	Replication Enzyme	Proofreading?	Mutation Rate
DNA viruses	DNA polymerase	Yes	Low
RNA viruses	RNA polymerase / reverse transcriptase	No	High

Note

Without proofreading, RNA viruses accumulate frequent errors, generating genetically diverse populations within a single host.

Hint

High mutation rates are risky for stability but beneficial for adaptability.

Intense Natural Selection:
Viruses face constant selective pressures from their hosts:
1. Immune defenses (e.g., antibodies targeting viral antigens)
2. Antiviral drugs
3. Transmission barriers between hosts
Variants with mutations that help them evade immunity or resist drugs survive and proliferate.

Definition

Paywall

(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Note

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam quis nostrud exercitation.

Excepteur sint occaecat cupidatat non proident

Tip

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

IB Biology Topic A2.3.6: Rapid Evolution in Viruses Notes

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

Why Do Viruses Evolve So Quickly?

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Why Do Viruses Evolve So Quickly?

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

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