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On HMS Beagle, Darwin noticed that finches on the Galápagos Islands had different beak shapes depending on the food on their island. Free notes and FAQs.
Darwin's Theory and Modern Evidence is part of The development of understanding of genetics and evolution in GCSE Edexcel Higher Biology.
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On HMS Beagle, Darwin noticed that finches on the Galápagos Islands had different beak shapes depending on the food on their island. Free notes and FAQs.
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Use this lesson to stay inside The development of understanding of genetics and evolution while connecting the detail back to the wider Topic 4: Natural selection and genetic modification topic.
Read the core explanations from Darwin's Theory and Modern Evidence before testing yourself from memory.
In 1859, Charles Darwin published a book that changed everything we thought we knew about life on Earth. His theory of evolution by natural selection was controversial at first, but today it's widely accepted by scientists worldwide. Here's why his idea was so powerful - and why it took time to catch on.
Darwin noticed something fascinating during his voyage on HMS Beagle. Animals on different islands looked similar but had slight differences. Finches on the Galápagos Islands, for example, had different beak shapes depending on what food was available on their particular island.
Darwin's theory had four key parts: variation exists within species, some variations are inherited, more offspring are produced than can survive, and those with advantageous traits are more likely to survive and reproduce. This process, repeated over many generations, leads to evolutionary change.
Darwin had one major problem with his theory. He could see that offspring resembled their parents, but he didn't know HOW characteristics were passed from one generation to the next. This was the missing piece that made some scientists sceptical.
The breakthrough came decades later when scientists discovered genes. We now know that characteristics are passed on to offspring through genes - sections of DNA that code for specific traits. This discovery provided the mechanism Darwin's theory needed.
**Trap**: Many students think characteristics are 'blended' like mixing paint. Actually, genes are discrete units that can be dominant or recessive. A brown-eyed parent and blue-eyed parent don't produce a child with 'medium brown' eyes - the child gets either brown or blue eyes depending on which genes are dominant.
Fossils are like a photo album of life on Earth, showing us what organisms looked like millions of years ago. The fossil record provides compelling evidence for Darwin's theory by showing how species have changed over time.
Look at horse evolution, for example. Fossils show that early horses were small, about the size of a dog, with multiple toes. Over millions of years, they gradually became larger with fewer toes, eventually developing into the single-toed horses we see today. This matches exactly what Darwin's theory predicts - gradual change over time.
The fossil record also shows the appearance of new species and the extinction of others. We can see transitional forms - fossils that show characteristics of both older and newer species. These 'missing links' fill in the gaps and show the gradual progression from one form to another.
You don't need to wait millions of years to see evolution happen. Antibiotic resistance in bacteria provides a perfect real-time example of natural selection in action. This is evolution happening fast enough for us to observe directly.
Worked example: How Antibiotic Resistance Evolves
Explain how bacteria develop resistance to antibiotics through natural selection.
Answer: Through natural selection, antibiotic resistance spreads through bacterial populations, making infections harder to treat.
This is exactly what Darwin predicted - individuals with advantageous characteristics (resistance) are more likely to survive and reproduce. The 'environment' (presence of antibiotics) selects for certain traits, and the population evolves.
Darwin's theory is now widely accepted because multiple lines of evidence all point to the same conclusion. It's not just one piece of evidence - it's the combination that makes the case so strong.
We have genetic evidence showing how traits are inherited, fossil evidence showing gradual change over time, and direct observation of evolution happening in bacteria, insects, and other organisms. When different types of evidence all support the same theory, scientists gain confidence in its validity.
The theory also makes testable predictions that have been confirmed. For example, it predicts that we should find transitional fossils, and we do. It predicts that organisms in similar environments should evolve similar solutions, and they do. This predictive power is what makes it a strong scientific theory.
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Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.
Genes are sections of DNA that control the development of specific characteristics and are passed from parents to offspring. Their discovery provided the mechanism of inheritance that Darwin's theory needed.
During his voyage on HMS Beagle, Darwin noticed that finches on the Galápagos Islands had different beak shapes depending on what food was available on their particular island. Animals on different islands looked similar but had slight differences.
Darwin's theory has four key parts: variation exists within species, some variations are inherited, more offspring are produced than can survive, and those with advantageous traits are more likely to survive and reproduce. Repeated over many generations, this leads to evolutionary change.
Darwin's theory is now widely accepted because multiple lines of evidence point to the same conclusion: genetic evidence showing how traits are inherited, fossil evidence showing gradual change over time, and direct observation of evolution in bacteria, insects and other organisms. Its predictions, such as transitional fossils, have also been confirmed.
Fossils show that early horses were small, about the size of a dog, with multiple toes. Over millions of years they gradually became larger with fewer toes, eventually developing into single-toed horses, which matches the gradual change over time that Darwin's theory predicts.
The discovery of genes provided the mechanism Darwin's theory needed, because Darwin did not know how characteristics were passed on. Genes are sections of DNA that control specific characteristics and are passed from parents to offspring as discrete units, not blended like mixing paint.
On his voyage on HMS Beagle, Darwin noticed that animals on different islands looked similar but had slight differences. Finches on the Galápagos Islands had different beak shapes depending on the food available on their particular island.
Characteristics are not blended like mixing paint, because genes are discrete units that can be dominant or recessive. A brown-eyed parent and a blue-eyed parent do not produce a child with medium brown eyes; the child gets either brown or blue eyes.
Darwin's theory predicts that transitional fossils should be found, and they are. It also predicts that organisms in similar environments should evolve similar solutions, and they do, which gives the theory its predictive power.
Resistant bacteria multiply rapidly after antibiotics because most competitors are dead, so they have more resources and space. They reproduce rapidly, so the next generation has a much higher proportion of resistant bacteria.
Darwin's theory was missing an explanation of how characteristics are passed from one generation to the next. Decades later, scientists discovered genes, sections of DNA passed to offspring, which provided this mechanism.