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Genetics and ecosystems official content
Genetics and ecosystems official content develops AQA A-Level Biology knowledge through Inheritance, Populations, Evolution may lead to speciation, Populations in ecosystems. Students should connect molecular detail, cell-level mechanisms, organism-level outcomes and ecological or genetic consequences where relevant, rather than treating each objective as an isolated definition. The topic overview should help learners locate every learning objective, recognise the main command words and prepare for data-led questions. Focus on precise biological vocabulary, cause-and-effect chains, and evidence from practical work or experimental observations. Useful revision links include genotype, phenotype., dominant,, recessive,, codominant,, homozygous, heterozygous, terminology., labelled, genetic. Strong answers should state the biological principle, apply it to the named context, interpret any data carefully and finish with a clear consequence or evaluation. Common mistakes include giving GCSE-level descriptions, missing the scale of organisation, or using a correct term without explaining why it matters in this A-Level context.
21
Objectives
10
Flashcards
10
Questions
90 min
Study time
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Syllabus checklist
What you need to know
21 objective pages available
Inheritance5 objectives
- Define genotype and phenotype.
- Use dominant, recessive, codominant, homozygous and heterozygous terminology.
- Use fully labelled genetic diagrams for monohybrid and dihybrid crosses.
- Interpret crosses involving sex-linkage, autosomal linkage, multiple alleles and epistasis.
- Use chi-squared testing to compare observed and expected phenotypic ratios.
Populations4 objectives
- Define a population as organisms of the same species in a space and time that can potentially interbreed.
- Explain gene pool and allele frequency.
- State the conditions under which the Hardy-Weinberg principle applies.
- Use the Hardy-Weinberg equation to calculate allele, genotype and phenotype frequencies.
Evolution may lead to speciation5 objectives
- Explain genetic and environmental causes of phenotypic variation.
- Explain differential survival and reproductive success in natural selection.
- Explain stabilising, directional and disruptive selection.
- Explain genetic drift and founder effects in small populations.
- Explain how reproductive isolation can lead to speciation.
Populations in ecosystems7 objectives
- Describe populations, communities, ecosystems and ecological niches.
- Explain effects of abiotic and biotic factors on population size.
- Explain succession and climax communities.
- Evaluate conservation methods and ecosystem management.
- Required practicals 10 and 12: investigate animal movement using a choice chamber or maze and investigate species distribution using sampling.
- Required practical 10: investigate animal movement using a choice chamber or maze.
- Required practical 12: investigate species distribution using sampling techniques.
Key terms
Exam tips
- Clarify definitions: Ensure you clearly define terms like genotype and phenotype in your answers.
- Use Punnett Squares: Always draw a Punnett square for genetic crosses to visualize allele combinations.
Common mistakes
- Confusing genotype with phenotype: Remember that genotype refers to the genetic makeup, while phenotype is the physical expression of those genes.
- Confusing Dominant and Recessive Alleles: Dominance refers to the expression of the allele, not its frequency in the population.
Practice preview
- Which of the following best defines the term 'genotype'?
- Explain the difference between genotype and phenotype.
- A genetic cross between two pea plants results in offspring with a 3:1 ratio of dominant to recessive traits. If the dominant trait is represented by 'A' and the recessive trait by 'a', what are the possible genotypes of the parent plants?
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