Edexcel A Level (IAL) Biology -5.23 Mutation, Natural Selection & Evolution- Study Notes- New Syllabus

Evolution Through Gene Mutation and Natural Selection

🌱 Introduction

Evolution happens when the frequency of alleles in a population changes across generations. Two main drivers of this change are:

• Gene mutation
• Natural selection

Together, they explain how species adapt and why populations look different over time.

🧪 Gene Mutation (the source of variation)

What is a mutation?

A mutation is a random change in DNA. It creates new alleles or alters existing ones.

Why mutations matter

• They introduce genetic variation.
• Without mutations, all individuals would have identical alleles and evolution could not occur.

🌿 Types of mutations (simple exam-friendly list)

• Beneficial → increases survival or reproduction
• Neutral → no effect
• Harmful → decreases survival

Key idea

Mutation = new allele enters the population → gives natural selection something to act on.

🦁 Natural Selection (the sorting process)

What natural selection does

• Individuals with advantageous alleles survive better and reproduce more.
• These alleles get passed on more often.
• Over generations, the population has more of the advantageous allele.

🧠 Memory Trick

Survive → Reproduce → Pass on → Increase
(How an advantageous allele becomes common)

🔄 How Mutation + Natural Selection Change Allele Frequency

• A mutation creates a new allele.
• If this allele is advantageous, organisms carrying it survive better.
• These survivors produce more offspring.
• More offspring carry the advantageous allele.
• Over time, the frequency of this allele increases.
• Harmful alleles become less common because individuals carrying them survive less.

This steady shift in allele proportions is evolution.

📊 Summary Table