AQA Biology Variation and evolution

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48 objective pages available

Variation9 objectives

Describe how the genome and interaction with the environment influence phenotype.
Define variation as differences in characteristics between individuals in a population.
Explain that variation may be caused by inherited genes.
Explain that variation may be caused by environmental conditions during development.
Explain that variation may be caused by a combination of genes and environment.
State that there is usually extensive genetic variation within a population of a species.
Recall that all variants arise from mutations.
Describe that most mutations have no effect on phenotype, some influence phenotype, and very few determine phenotype.
Explain how a rare mutation producing a suitable new phenotype can lead to a relatively rapid change in a species.

Evolution8 objectives

Describe evolution as a change in inherited characteristics of a population over time.
Explain that evolution occurs through natural selection.
Explain that natural selection may result in the formation of a new species.
State that living species evolved from simple life forms that first developed more than three billion years ago.
Explain how variants with phenotypes best suited to an environment are selected.
Explain that selected individuals are more likely to survive, breed and pass on characteristics.
Explain that two populations form new species if phenotype differences mean they can no longer interbreed to produce fertile offspring.
Use the theory of evolution by natural selection in an explanation.

Selective breeding8 objectives

Describe selective breeding as humans breeding plants and animals for particular genetic characteristics.
Explain the impact of selective breeding on food plants and domesticated animals.
Describe choosing parents with desired characteristics from a mixed population.
Explain that selected parents are bred, then offspring with desired characteristics are bred over many generations.
Identify useful or appearance-based traits selected by humans, including disease resistance, more meat or milk, gentle dog nature and large or unusual flowers.
Explain that selective breeding can lead to inbreeding.
Explain that inbreeding can make some breeds prone to disease or inherited defects.
Explain benefits, risks and ethical issues of selective breeding when given appropriate information.

Genetic engineering13 objectives

Describe genetic engineering as modifying the genome of an organism by introducing a gene from another organism.
Explain that genetic engineering can give an organism a desired characteristic.
Describe crop plants engineered for disease resistance or bigger and better fruits.
Describe bacterial cells engineered to produce useful substances such as human insulin.
Explain potential benefits and risks of genetic engineering in agriculture.
Explain potential benefits and risks of genetic engineering in medicine.
Describe objections some people have to genetic engineering and GM crops.
Explain that GM crops may be resistant to insect attack or herbicides and may have increased yields.
Explain concerns about effects of GM crops on wild flowers, insects and human health.
Describe (HT only) that enzymes isolate the required gene in genetic engineering.
Describe (HT only) inserting the required gene into a vector such as a bacterial plasmid or virus.
Describe (HT only) using the vector to insert the gene into the required cells at an early stage of development.
Interpret information about genetic engineering techniques and make informed judgements about cloning, genetic engineering and GM crops.

Cloning (biology only)10 objectives

Describe tissue culture as using small groups of plant cells to grow identical new plants.
Explain why tissue culture is useful for preserving rare plant species and commercial nurseries.
Describe cuttings as an older simple method for producing identical new plants from a parent plant.
Describe embryo transplants as splitting cells from an early animal embryo and transplanting identical embryos into host mothers.
Describe adult cell cloning by removing the nucleus from an unfertilised egg cell.
Describe inserting the nucleus from an adult body cell into the enucleated egg cell.
Explain that an electric shock stimulates the egg cell to divide to form an embryo.
Explain that embryo cells from adult cell cloning contain the same genetic information as the adult body cell.
Describe inserting the embryo into a womb after it has developed into a ball of cells.
Explain potential benefits and risks of cloning in agriculture and medicine and ethical objections.

environmentgenomepopulationvariationExplainspeciesmutationsvariantsphenotypenew phenotypeevolutioninherited characteristics

Variation exam tip 1: Use precise biological vocabulary when you explain how to describe how the genome and interaction with the environment influence phenotype..
Variation exam tip 1: Use precise biological vocabulary when you explain how to define variation as differences in characteristics between individuals in a population..

Variation common mistake 1: Answer by clearly explaining how to describe how the genome and interaction with the environment influence phenotype..
Variation common mistake 1: Answer by clearly explaining how to define variation as differences in characteristics between individuals in a population..

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