Edexcel GCSE Biology Topic 4: Natural Selection and Genetic Modification Exam Questions

About Edexcel GCSE Biology Topic 4: Natural Selection and Genetic Modification

Topic 4 of Edexcel GCSE Biology is assessed on Paper 1. It explores the evidence for human evolution from fossils and stone tools, Darwin's theory of evolution by natural selection, and how classification has changed with genetic analysis. It then covers how humans change organisms by selective breeding and genetic engineering, with GCSE Biology students also studying tissue culture and the use of fertilisers and biological control. Examiners often ask you to describe the evidence from Ardi, Lucy and the Leakey finds, explain antibiotic resistance as natural selection, and evaluate genetically modified organisms.

What you need to know

• Evidence for human evolution Fossils of Ardi (about 4.4 million years old), Lucy (about 3.2 million years old) and the finds of Richard Leakey and his team (about 1.6 million years old, such as Turkana Boy) show changes in brain size, walking upright and limb structure. Stone tools become more complex over time and can be dated using the rock layers they are found in.
• Darwin and natural selection Variation exists in a population; individuals best adapted to the environment are more likely to survive and reproduce, passing on their alleles. Antibiotic resistance in bacteria is evidence for evolution happening now.
• Classification Organisms were classified into five kingdoms. Developments in genetic analysis led Carl Woese to propose the three-domain system: Archaea, Bacteria and Eukarya. The pentadactyl limb is evidence of common ancestry (Biology only).
• Selective breeding Humans select parents with desirable characteristics and breed them over many generations, for example for high yield or disease resistance. Risks include reduced genetic variation.
• Tissue culture (Biology only) Small pieces of plant tissue are grown on a nutrient medium in sterile conditions to produce many identical plants quickly, useful for rare species and commercial crops.
• Genetic engineering A gene is transferred from one organism to another. Higher tier: restriction enzymes cut out the gene and cut open a plasmid vector, leaving sticky ends; ligase joins them; the recombinant plasmid is inserted into bacteria, for example to make human insulin. GM crops can be pest or herbicide resistant.
• Fertilisers and biological control (Biology only) Fertilisers increase crop yield but can cause eutrophication. Biological control uses a natural predator or parasite to reduce a pest, but the control organism may itself become a pest.

Common mistakes in Topic 4: Natural Selection and Genetic Modification

• Saying humans evolved from chimpanzees. Humans and chimpanzees share a common ancestor.
• Saying bacteria become resistant by getting used to antibiotics. Resistance arises by random mutation and spreads by natural selection.
• Mixing up ligase and restriction enzymes. Restriction enzymes cut DNA; ligase joins DNA fragments.
• Saying selective breeding is the same as genetic engineering. Selective breeding works over generations with existing alleles; genetic engineering transfers specific genes directly.
• Giving one-sided GM evaluations. Include benefits such as increased yield and risks such as effects on wild populations or long-term health uncertainty.

Try three Topic 4: Natural Selection and Genetic Modification exam-style questions