New species arise when genetic differences lead to an inability of members of the populations to interbreed and produce fertile offspring
A new species forms when two populations become so genetically different that they can no longer breed together to produce fertile offspring.
Real World
The Kaibab squirrel on the north rim of the Grand Canyon diverged from the Abert's squirrel on the south rim after the canyon separated them roughly five million years ago, and the two populations can no longer interbreed.
Exam Focus
Always state both conditions: reproductively isolated AND unable to produce fertile offspring — one alone loses marks.
Evaluation Scaffold
A four-step framework for high-quality evaluation. Use this for 'assess', 'evaluate', and 'to what extent' questions.
How well did you know this?