Speciation VCE Biology 3/4

Unit 4 AOS 2

Speciation

The process by which populations genetically diverge until they become different species.

What is allopatric speciation?

Formation of new species after populations become geographically isolated.

What is sympatric speciation?

Formation of new species among populations living in the same geographical location.

What is a subspecies?

A population that may differ phenotypically from others but can still breed with them to produce viable, fertile offspring.

What is the first stage of allopatric speciation?

Separate populations of the original species form; gene flow may initially continue.

What is geographical isolation?

A physical barrier separates populations and prevents gene flow between them.

Name four possible causes of geographical isolation.

Rivers, mountains, continental drift, rising sea levels or climate change.

What is gene flow?

The exchange of genetic material between populations.

How does geographical isolation affect gene flow?

It prevents exchange of genetic material between the isolated populations.

What happens after populations become isolated?

Different selection pressures favour different traits, causing allele frequencies to diverge.

How do differences accumulate during allopatric speciation?

Mutation and different selection pressures lead to genetic differences between isolated populations over time.

What is reproductive isolation?

Populations can no longer interbreed, even if a geographical barrier is removed.

List the four main steps of allopatric speciation.

Separate populations form; geographic isolation stops gene flow; different selection pressures change allele frequencies; genetic divergence causes reproductive isolation and separate species.

How do Galapagos finches illustrate allopatric speciation?

Populations from an ancestral mainland species spread across 19 islands with different selection pressures, and multiple species formed over time.

How does sympatric speciation begin?

Different selection pressures act on different phenotypes within one population in the same location.

How does sympatric speciation lead to new species?

Groups become reproductively isolated, and genetic differences accumulate until distinct species form.

How do Howea palms on Lord Howe Island illustrate sympatric speciation?

Different soil pH caused different flowering times, reproductively isolating early- and late-flowering groups that diverged into two species.

What is the key difference between allopatric and sympatric speciation?

Allopatric speciation involves geographic isolation; sympatric speciation occurs in the same geographic location.

Why does speciation generally take time?

Genetic differences must accumulate until populations become reproductively isolated.

If a barrier is removed, what distinguishes fully formed species in the allopatric model?

They remain reproductively isolated and do not interbreed.