AQA GCSE Biology 4.6.3 The Development of Understanding of Genetics and Evolution Exam Questions

About AQA GCSE Biology 4.6.3 The Development of Understanding of Genetics and Evolution

This section of AQA Inheritance, variation and evolution, examined on Paper 2, looks at how scientists built up our understanding of evolution and inheritance, and at the evidence that supports it. All students study evidence for evolution, fossils, extinction and antibiotic resistant bacteria. GCSE Biology students also study Darwin's theory and why it was slow to be accepted, Lamarck's alternative idea, Wallace and speciation, and Mendel's work on inheritance. Examiners often ask why Darwin's theory was controversial, why fossil evidence is incomplete, and how to reduce the development of resistant strains such as MRSA.

What you need to know

• Darwin and Lamarck (Biology only) Darwin proposed evolution by natural selection after the voyage of HMS Beagle and published On the Origin of Species in 1859. It was slow to be accepted because it challenged the idea that God created all life, there was not enough evidence at the time, and the mechanism of inheritance was not known. Lamarck proposed that changes acquired in a lifetime are inherited, which is not supported.
• Wallace and speciation (Biology only) Alfred Russel Wallace independently proposed natural selection and worked on warning colouration. Speciation happens when populations become isolated, natural selection acts differently on each, and they can no longer interbreed to produce fertile offspring.
• Mendel and genetics (Biology only) Gregor Mendel carried out breeding experiments on pea plants in the mid-19th century and showed characteristics are determined by inherited units. Later, chromosomes were observed, then genes were linked to chromosomes, and in the mid-20th century the structure of DNA was determined.
• Evidence for evolution Evolution is supported by fossils and by antibiotic resistance in bacteria, which shows evolution happening quickly.
• Fossils Fossils are remains of organisms from millions of years ago found in rocks. They form when parts do not decay because conditions are unsuitable for decay, when parts are replaced by minerals, or as traces such as footprints. Many early forms were soft-bodied and fossils have been destroyed by geological activity, so the record is incomplete.
• Extinction Extinction can be caused by new predators, new diseases, more successful competitors, or changes to the environment over geological time, including catastrophic events.
• Resistant bacteria Bacteria reproduce rapidly so resistant strains such as MRSA spread quickly. Reduce resistance by not prescribing antibiotics for viral or non-serious infections, completing courses, and restricting agricultural use. Developing new antibiotics is costly and slow.

Common mistakes in 4.6.3 The Development of Understanding of Genetics and Evolution

• Describing Lamarck's idea as correct. Characteristics acquired during a lifetime are not passed on genetically.
• Saying Darwin knew about genes. The mechanism of inheritance was not understood at the time, which is one reason the theory was slow to be accepted.
• Saying fossils are bones only. Fossils include mineralised remains, preserved remains and traces such as footprints and burrows.
• Saying bacteria become resistant because they get used to the antibiotic. A mutation gives resistance and natural selection increases the proportion of resistant bacteria.

Try three 4.6.3 The Development of Understanding of Genetics and Evolution exam-style questions