The Process of Speciation Revision Notes | GCSE OCR Foundation Biology

What this lesson covers

Learn the step-by-step process that leads to the formation of new species, building on the foundational work of Wallace and modern understanding of spec...

• Describe the process of speciation and the steps that lead to new species formation
• Explain how geographical isolation can lead to the populations can no longer interbreed
• Explain how geographical isolation can lead to new species
• Evaluate the role of natural selection in driving speciation

Key ideas to keep in view

Use this lesson to stay inside B5.2 Natural selection and evolution while connecting the detail back to the wider B5: Genes, inheritance and selection topic.

• B5: Genes, inheritance and selection
• B5.2 Natural selection and evolution
• GCSE OCR Foundation Biology

Lesson notes preview

Read the core explanations from The Process of Speciation before testing yourself from memory.

• Imagine two groups of the same animal living on opposite sides of a mountain range. Over thousands of years, they become so different they can no longer breed together. This is speciation - one of evolution's most dramatic tricks.
• A group of organisms that can interbreed to produce fertile offspring. Members of different species cannot produce fertile offspring together.
• The key word here is 'fertile'. A horse and donkey can mate to produce a mule, but mules are sterile - they cannot reproduce. This proves horses and donkeys are separate species, despite being similar.
• Trap: Many students think species are just animals that look similar. Actually, appearance can be misleading - some very different-looking animals are the same species, while some identical-looking ones are different species.
• Speciation doesn't happen overnight. It's a step-by-step process that can take thousands or millions of years. Here's how populations split into separate species:
• The crucial point is step 2 - isolation. Without some barrier preventing interbreeding, gene flow continues and the population remains as one species. This barrier is usually geographical, but it can also be behavioural or temporal.
• Not all isolation is the same. The type of barrier that separates populations affects how quickly and dramatically speciation occurs.
• Physical separation of populations by geographical barriers such as mountains, rivers, or oceans that prevent interbreeding.
• Geographical isolation is the most common cause of speciation. When continents drift apart, mountains form, or sea levels change, populations get cut off from each other. The Galápagos finches are a classic example - different islands led to different species.
• But isolation isn't always about physical barriers. Populations can become reproductively isolated in other ways:

Continue through the topic

Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.