AQA GCSE FOUNDATION Biology: Evolution and Natural Selection

AQA GCSE Foundation Biology: Evolution and Natural Selection

Introduction

Evolution is the process of change in the inherited characteristics of a population over time. Natural selection is a key mechanism of evolution. This tutorial will explore the theories and evidence for species adaptation through natural selection.

Theories of Evolution

• Charles Darwin's Theory: In the 19th century, Charles Darwin proposed the theory of evolution by natural selection. He observed that organisms within a population show variation, and those with traits that make them better suited to their environment are more likely to survive, reproduce, and pass on those advantageous traits. This leads to a gradual change in the population over generations.

• Jean-Baptiste Lamarck's Theory: Lamarck proposed that organisms can inherit characteristics acquired during their lifetime, known as "inheritance of acquired characteristics." For example, he suggested that giraffes developed long necks by stretching to reach high leaves. This theory has been largely discredited, as acquired traits are not typically passed down genetically.

Evidence for Evolution

• Fossil Record: Fossils provide evidence of extinct organisms and show how life forms have changed over time. The fossil record reveals a progression from simpler to more complex organisms, supporting the idea of evolution.

• Comparative Anatomy: Comparing the anatomy of different species reveals similarities and differences that suggest common ancestry. For example, the bone structure of a human arm, a bat wing, and a whale flipper are remarkably similar, indicating a common ancestor.

• DNA Evidence: DNA analysis provides strong evidence for evolution. The more closely related two species are, the more similar their DNA sequences. This supports the idea that all life forms share a common ancestor.

• Biogeography: The distribution of species around the world also supports evolution. Species that live in similar environments often share traits, but their location on Earth can indicate how they evolved.

Natural Selection

Natural selection is the driving force behind evolution. It is the process by which organisms with traits that make them better suited to their environment survive and reproduce more successfully than those with less advantageous traits.

Key Principles of Natural Selection:

• Variation: Individuals within a population show variation in their traits.
• Inheritance: These variations are inherited from parents to offspring.
• Competition: Organisms compete for resources like food, water, and mates.
• Survival and Reproduction: Individuals with advantageous traits are more likely to survive and reproduce, passing on those traits.

Examples of Natural Selection:

• Peppered Moth: The peppered moth population in England showed a change in coloration during the Industrial Revolution. Dark moths became more common due to their better camouflage against soot-covered trees.

• Antibiotic Resistance: The overuse of antibiotics has led to the selection of bacteria resistant to those antibiotics. These resistant bacteria survive and reproduce, spreading resistance to the wider population.

Conclusion

Evolution by natural selection is a powerful force that has shaped the diversity of life on Earth. Understanding evolution helps us to appreciate the interconnectedness of living organisms and the importance of protecting biodiversity.