Explain how sympatric speciation can occur within a single population occupying the same geographic area.

Sympatric speciation occurs within a single interbreeding population that occupies the same geographic area, so there is no physical barrier to gene flow.

Reproductive isolation can arise through several mechanisms:
1. Polyploidy – a chromosome duplication event creates a new, reproductively isolated group.
2. Resource or habitat specialisation – individuals specialise on different resources or micro‑habitats, reducing interbreeding.
3. Disruptive selection – strong selection on extreme phenotypes creates two sub‑groups that preferentially mate within their own group.

As these mechanisms reduce gene flow, genetic differences accumulate between the sub‑groups. Over time the divergence becomes sufficient that the sub‑groups can no longer interbreed or produce fertile offspring, completing speciation.