---
title: "Allopatric Speciation — AP Bio Definition & Exam Guide"
description: "Allopatric speciation happens when a physical barrier splits a population, cutting off gene flow until two species form. Key to Unit 7 speciation and FRQs."
canonical: "https://fiveable.me/ap-bio/key-terms/allopatric-speciation"
type: "key-term"
subject: "AP Biology"
---

# Allopatric Speciation — AP Bio Definition & Exam Guide

## Definition

Allopatric speciation is a mode of speciation that occurs when biological populations become geographically isolated from each other to an extent that prevents or interferes with genetic interchange.

## Related Study Guides

- [7.10 Speciation](/ap-bio/unit-7/speciation/study-guide/EvkCBpDW4LggHrVIepHo)

## Review

### Related Terms

- Geographic Isolation: This refers to a population of animals, plants, or other organisms that are separated from exchanging genetic material with other organisms of the same species.
- [Genetic Drift](/ap-bio/key-terms/genetic-drift): This is variation in the relative frequency of different genotypes in a small population, owing to the chance disappearance of particular genes as individuals die or do not reproduce.
- [Founder Effect](/ap-bio/key-terms/founder-effect): The reduced genetic diversity which results when a population is descended from a small number of colonizing ancestors.