Evidence for Evolution Revision Notes | GCSE OCR Foundation Biology

What this lesson covers

Explore the key evidence that supports the theory of evolution, including fossil records and antibiotic resistance in bacteria. Learn how these examples...

• Describe the evidence for evolution provided by fossils
• Explain how antibiotic resistance in bacteria supports evolutionary theory
• Compare different types of fossil evidence and their limitations
• Evaluate the strength of evidence from fossils versus modern examples

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 Evidence for Evolution before testing yourself from memory.

• Evolution happened over millions of years - we can't watch it happen. So how do we know it's real? Scientists need solid evidence to support Darwin's theory. Think of it like a detective story: we weren't there when the 'crime' happened, but we can piece together what occurred from the clues left behind.
• The two strongest pieces of evidence come from completely different sources. Fossils show us evolution from the distant past - like ancient photographs frozen in rock. Antibiotic resistance shows us evolution happening right now in hospital laboratories.
• 2. Fossil Evidence - Ancient Photographs in Rock
• Fossils form when organisms die and get buried quickly in sediment. Over millions of years, the sediment turns to rock and the organism's remains are preserved. Picture layers of rock like pages in a history book - the deeper you go, the older the fossils become.
• The collection of all fossils discovered and placed in chronological order, showing how life has changed over time.
• The fossil record shows three key pieces of evidence for evolution. First, simpler organisms appear in older rock layers, while more complex ones appear in newer layers. Second, many fossils show features that are intermediate between different groups - like Archaeopteryx, which has both reptile and bird characteris...
• Trap: Many students think fossils show sudden appearance of new species. Actually, fossils show gradual change over millions of years - the gaps exist because fossilisation is rare and we haven't found every intermediate form yet.
• 3. Antibiotic Resistance - Evolution in Real Time
• Antibiotic resistance gives us a perfect example of natural selection happening fast enough to observe. When bacteria are exposed to antibiotics, most die - but a few have random mutations that make them resistant. These survivors reproduce rapidly, passing on their resistance genes.
• This process happens incredibly quickly because bacteria reproduce every 20 minutes. What takes millions of years in larger organisms can happen in days or weeks with bacteria. MRSA (methicillin-resistant Staphylococcus aureus) is a real example that has evolved in hospitals worldwide.

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.