Formation of New Species Revision Notes | GCSE OCR Foundation Biology

What this lesson covers

Understanding how populations become so different that they can no longer interbreed to produce fertile offspring, resulting in the formation of new spe...

• Explain how populations of the same species can become reproductively isolated
• Describe the process by which new species form from existing ones
• Analyse examples of speciation in different environments
• Evaluate evidence for species formation in natural populations

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 Formation of New Species before testing yourself from memory.

• Picture two animals that look almost identical - a horse and a donkey. They can mate and produce offspring called mules. But here's the catch: mules are sterile. They can't have babies of their own.
• This tells us something crucial about what makes a species. It's not just about looking similar or being able to mate - it's about producing fertile offspring that can continue the genetic line.
• A group of organisms that can interbreed to produce fertile offspring. Members of the same species share similar characteristics and can pass on their genes to the next generation.
• Trap: Many students think species are just animals that look alike. Actually, appearance can be misleading - some very different-looking animals are the same species, whilst some identical-looking ones are different species entirely.
• Imagine a population of beetles living in a forest. A new river forms, splitting the forest in half. Now we have two separate populations that can't reach each other to mate.
• Over many generations, these separated populations face different environmental pressures. The beetles on one side might encounter different predators, food sources, or climate conditions. Through natural selection, each population gradually develops different characteristics.
• When populations of the same species become separated and can no longer interbreed to produce fertile offspring. This can happen due to geographical barriers (like rivers or mountains), behavioural differences, or genetic changes.
• This separation can be the first step towards forming new species. But isolation alone isn't enough - the populations need time to change.
• Here's where it gets fascinating. After thousands of generations apart, our beetle populations have changed so much that even if the river dried up, they couldn't successfully interbreed anymore.
• Maybe their mating calls have changed, their breeding seasons have shifted, or their chromosomes have become incompatible. When they try to mate, either nothing happens, or they produce offspring that can't survive or reproduce.

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.