GCSE Biology revision

Speciation (biology only)

The development of understanding of genetics and evolution

AQA 4.1.1.1

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AQA student objectives

Learning pathway

All · Most · Some

ALL 🎯

Identify and describe Alfred Russel Wallace and His Contribution, What Is Speciation? and The Role of Geographical Isolation in the context of speciation (biology only).

MOST 🎯🎯

Explain the relationships between Alfred Russel Wallace and His Contribution, What Is Speciation? and The Role of Geographical Isolation and how they contribute to speciation (biology only).

SOME 🎯🎯🎯

Apply and analyse knowledge of Alfred Russel Wallace and His Contribution, What Is Speciation? and The Role of Geographical Isolation to interpret unfamiliar information about speciation (biology only).

Revision summary

Key knowledge

Read on screen, then print for Cornell-style active revision.

Alfred Russel Wallace and His Contribution

Alfred Russel Wallace was a contemporary of Charles Darwin who independently developed ideas about natural selection and evolution.
Wallace is most famously associated with his work on speciation, proposing that natural selection can lead to the formation of new species.
Darwin and Wallace's simultaneous work created competition, which prompted Darwin to publish 'On the Origin of Species'.

1. Alfred Russel Wallace and His ContributionAQA

Notes

Alfred Russel Wallace was a contemporary of Charles Darwin who independently developed ideas about natural selection and evolution.
Wallace is most famously associated with his work on speciation, proposing that natural selection can lead to the formation of new species.
Darwin and Wallace's simultaneous work created competition, which prompted Darwin to publish 'On the Origin of Species'.

What Is Speciation?

Speciation is the process by which two populations become so different from one another that they can no longer interbreed to produce fertile offspring.
Speciation begins when a single population is split into two separate, isolated groups.
Natural selection acting on each isolated population over time drives the two groups to become increasingly different.

2. What Is Speciation?AQA

Notes

Speciation is the process by which two populations become so different from one another that they can no longer interbreed to produce fertile offspring.
Speciation begins when a single population is split into two separate, isolated groups.
Natural selection acting on each isolated population over time drives the two groups to become increasingly different.

The Role of Geographical Isolation

Geographical isolation occurs when a physical barrier, such as a river or mountain range, separates a population into two groups.
Once separated, the two populations no longer interbreed, so genetic changes in one group cannot spread to the other.
Geography is one example of how populations can be split, but other factors — such as a group being introduced to a new area — can also cause isolation.

3. The Role of Geographical IsolationAQA

Notes

Geographical isolation occurs when a physical barrier, such as a river or mountain range, separates a population into two groups.
Once separated, the two populations no longer interbreed, so genetic changes in one group cannot spread to the other.
Geography is one example of how populations can be split, but other factors — such as a group being introduced to a new area — can also cause isolation.

Mutations and Natural Selection Within an Isolated Population

A mutation is a random change in an organism's DNA that may give an individual a survival advantage, such as improved ability to climb trees and access food.
Beneficial mutations spread through a population via natural selection, as individuals with the advantageous trait are more likely to survive and reproduce.
Over generations, the advantageous trait becomes more frequent within the isolated population through the process of natural selection.

4. Mutations and Natural Selection Within an Isolated PopulationAQA

Notes

A mutation is a random change in an organism's DNA that may give an individual a survival advantage, such as improved ability to climb trees and access food.
Beneficial mutations spread through a population via natural selection, as individuals with the advantageous trait are more likely to survive and reproduce.
Over generations, the advantageous trait becomes more frequent within the isolated population through the process of natural selection.

Divergence of Isolated Populations

Because the two isolated populations are not interbreeding, different mutations and adaptations accumulate independently in each group.
Over time, the genetic differences between the two populations become so great that they are considered separate species.
The key criterion that defines two groups as different species is their inability to interbreed and produce fertile offspring.

5. Divergence of Isolated PopulationsAQA

Notes

Because the two isolated populations are not interbreeding, different mutations and adaptations accumulate independently in each group.
Over time, the genetic differences between the two populations become so great that they are considered separate species.
The key criterion that defines two groups as different species is their inability to interbreed and produce fertile offspring.

Defining a Species

A species is defined as a group of organisms that can interbreed with one another to produce fertile offspring.
Individuals from two different species cannot produce fertile offspring, which is the fundamental distinction between species.
This definition is central to understanding speciation and is important to state clearly in exam answers.

6. Defining a SpeciesAQA

Notes

A species is defined as a group of organisms that can interbreed with one another to produce fertile offspring.
Individuals from two different species cannot produce fertile offspring, which is the fundamental distinction between species.
This definition is central to understanding speciation and is important to state clearly in exam answers.

Common Misconceptions About Speciation

It is false that populations must always be separated by geography for speciation to occur — other forms of isolation are also possible.
It is false that different species can breed to produce fertile offspring — this ability is what defines members of the same species.
It is true that natural selection is required for speciation, as it drives the two isolated populations to diverge genetically over time.

7. Common Misconceptions About SpeciationAQA

Notes

It is false that populations must always be separated by geography for speciation to occur — other forms of isolation are also possible.
It is false that different species can breed to produce fertile offspring — this ability is what defines members of the same species.
It is true that natural selection is required for speciation, as it drives the two isolated populations to diverge genetically over time.

Summary of the Speciation Process

Step 1: A single population is split into two isolated groups by a barrier such as a river or a new geographical location.
Step 2: Different mutations arise and are selected for independently in each population through natural selection.
Step 3: Over many generations, the two populations become so genetically different that they can no longer interbreed to produce fertile offspring, forming two distinct species.

8. Summary of the Speciation ProcessAQA

Notes

Step 1: A single population is split into two isolated groups by a barrier such as a river or a new geographical location.
Step 2: Different mutations arise and are selected for independently in each population through natural selection.
Step 3: Over many generations, the two populations become so genetically different that they can no longer interbreed to produce fertile offspring, forming two distinct species.