AQA GCSE Biology 4.6.2 Variation and Evolution Exam Questions

About AQA GCSE Biology 4.6.2 Variation and Evolution

Variation and evolution is part of AQA Inheritance, variation and evolution, examined on Paper 2. It explains where variation comes from, how natural selection leads to evolution, and how humans change organisms by selective breeding and genetic engineering. GCSE Biology students also learn cloning methods: tissue culture, cuttings, embryo transplants and adult cell cloning. Higher tier students need the steps of genetic engineering. Examiners often ask you to explain natural selection step by step, describe how to selectively breed for a characteristic, and evaluate the benefits and risks of GM crops and cloning.

What you need to know

• 4.6.2.1 Variation Differences in characteristics within a population may be due to genes, the environment, or a combination of both. There is usually extensive genetic variation within a population of a species.
• Mutation Mutations occur continuously. Very rarely a mutation leads to a new phenotype; if it suits an environmental change it can lead to a relatively rapid change in the species.
• 4.6.2.2 Evolution Evolution is a change in the inherited characteristics of a population over time through natural selection, which may result in the formation of a new species. Individuals with characteristics best suited to the environment are more likely to survive, breed and pass on their alleles. Two populations become different species when they can no longer interbreed to produce fertile offspring.
• 4.6.2.3 Selective breeding Humans choose parents with desired characteristics, breed them, choose the best offspring and repeat over many generations. Examples: disease resistance in crops, more meat or milk, gentle dogs, large or unusual flowers. Inbreeding can make some breeds prone to disease or defects.
• 4.6.2.4 Genetic engineering A gene from one organism is cut out and transferred to another, for example the human insulin gene into bacteria, or genes for pest resistance or bigger fruit into GM crops. Higher tier: enzymes isolate the gene, it is inserted into a vector such as a plasmid or virus, and the vector inserts it into cells, which for plants and animals must be at an early stage of development.
• 4.6.2.5 Cloning (Biology only) Tissue culture uses small groups of cells to grow identical plants; cuttings are an older method. Embryo transplants split cells from an early embryo and implant them into host mothers. In adult cell cloning, the nucleus from an adult body cell is inserted into an enucleated egg cell, an electric shock stimulates division, and the embryo is implanted into a host.

Common mistakes in 4.6.2 Variation and Evolution

• Saying organisms adapt or change because they need to. Variation already exists due to mutation; the environment selects individuals that happen to be better suited.
• Saying individuals evolve. Populations evolve over many generations; individuals do not.
• Confusing selective breeding with genetic engineering. Selective breeding chooses parents over generations; genetic engineering transfers a gene directly.
• Saying a clone from adult cell cloning is identical to the egg donor or host. It is genetically identical to the animal that provided the body cell nucleus.
• Saying all mutations are harmful. Most have no effect on phenotype, and a few are beneficial.

Try three 4.6.2 Variation and Evolution exam-style questions