Inheritance, variation and evolution

Inheritance, variation and evolution is a cornerstone of GCSE Combined Science, exploring how traits are passed from parents to offspring and how species change over time. You'll learn about DNA, genes, and chromosomes, and how sexual reproduction generates genetic variation. This topic also covers the mechanisms of evolution by natural selection, including evidence from fossils and antibiotic resistance in bacteria. Understanding these ideas is essential for grasping how life on Earth has diversified and how we can apply this knowledge to medicine, agriculture, and conservation.

The topic builds on earlier work on cells and reproduction, and connects to ecology and biodiversity. You'll study the structure of DNA, the role of alleles in inheritance, and how genetic diagrams (Punnett squares) can predict the probability of traits. You'll also explore the process of evolution, including the work of Darwin and Wallace, and how selective breeding and genetic engineering are used by humans. This knowledge is not only tested in exams but also relevant to modern issues like the development of new medicines and the impact of climate change on species.

Mastering this topic requires understanding both the molecular basis of inheritance and the larger-scale patterns of evolution. You'll need to recall key terms like genotype, phenotype, homozygous, and heterozygous, and apply them to genetic crosses. You'll also need to evaluate evidence for evolution, such as the fossil record and molecular comparisons. By the end, you should be able to explain how variation arises and why some individuals are better adapted to their environment, leading to evolutionary change.