Patterns of biological change

For patterns of biological change  VCE Biology requires knowledge about allopatric speciation, divergent and convergent evolution and extinction.

Allopatric speciation

Allopatric speciation occurs when members of a population are split into separate groups, each of which is exposed to different selective forces. This often occurs in response to particular individuals being geographically isolated from the rest of a population such as by a river, mountains or islands. After a period of time, the selective pressures cause two distinct gene pools to develop that eventuate into two different species.

Types of evolution

Divergent evolution

  • Evolution of different species from a common ancestral species, due to factors such as natural selection and genetic drift.
  • Over time species accumulate genetic and homologous structural differences.

Adaptive radiation (special type of divergent speciation)

  • Rapid divergence of an evolutionary lineage from a recent common ancestor, this is due to adaptation to different habitats and islands in the absence of competition. This results in many new species that occupy different niches in a short period of time.
  • Evidence of this comes from clusters of related species.

Convergent evolution

A type of evolution when similar features develop independently for organisms that are not closely related.This results from species living in similar environments , performing similar roles in the ecosystem and natural selection.


  • This occurs when a species ceases to exist.
  • This may occur in response to environmental changes that are too rapid to allow adaptation.
  • Little variation in the population puts species at risk of extinction if sudden environmental change occurs.

Humans over time have had a role in the extinction of some species due to the following actions:

  • Destruction of habitats.
  • Introduction of feral species.
  • Exploitation and poaching of species.
  • Global warming.

See also