Variation can split a lineage.

A mutation is a change in DNA sequence. Mutations can arise during replication or from mutagens; many are neutral, some harmful and some beneficial in a given environment. Inherited mutations supply new alleles for evolutionary processes.

When populations become isolated, gene flow falls. Mutation, selection and drift can then change them independently. Over enough generations, reproductive isolation may develop and the populations can become separate species.

INTERACTIVE MODEL

Diverging populations

Gene flow 25% · partial divergence is possibleGene flow between populations25%IsolatedConnected

Explore: Adjust gene flow and see whether two populations diverge or remain similar.

\text{isolation}\to\text{divergence}\to\text{reproductive isolation}

WORKED EXAMPLE

A river separates one population into two.

Reduced gene flow allows allele frequencies to diverge.
If reproductive isolation develops, speciation may occur.

Assumed knowledge

Alleles and natural selection.

Learning checkpoints & source

YOUR LEARNING CHECKPOINT

Identify mutation as a source of new alleles.
Explain how isolation can support speciation.

QCAA Biology · Unit 4 · Continuity of life on Earth ↗

READY TO TRY IT?

Variation can split a lineage.

Diverging populations

A river separates one population into two.

Put the idea to work.