A-Level Biology Revision — Inheritance & Selection
Revise Inheritance & Selection for A-Level Biology. Step-by-step explanation, worked examples, common mistakes and exam-style practice aligned to AQA, Edexcel, OCR, WJEC, Eduqas, CCEA, Cambridge International (CIE), Pearson Edexcel International, OxfordAQA International, SQA, IB, AP.
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- Inheritance & Selection in A-Level Biology: explanation, examples, and practice links on this page.
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What is Inheritance & Selection?
Inheritance is the process by which genetic information is passed on from parent to offspring. A-Level Biology explores Mendelian inheritance, including monohybrid and dihybrid crosses, codominance, and sex linkage. Natural selection, the driving force of evolution, acts on the variation within a population, with individuals possessing advantageous alleles being more likely to survive, reproduce, and pass on these alleles.
Board notes: All A-Level Biology boards (AQA, Edexcel, OCR) cover Mendelian genetics, natural selection, and speciation. The use of the chi-squared test to analyse genetic cross data is a key statistical skill required by all boards. Specific examples of selection and speciation may vary.
Step-by-step explanationWorked examples
Worked example 1: Core method
In a monohybrid cross between two heterozygous parents (e.g., Bb), the predicted ratio of genotypes in the offspring is 1 BB : 2 Bb : 1 bb. The predicted ratio of phenotypes is 3 dominant (e.g., brown eyes) : 1 recessive (e.g., blue eyes). This can be shown using a Punnett square.
Worked example 2: Exam variation
Now change one detail in the question and keep the same structure: name the Inheritance & Selection idea being tested, show the method or evidence, then explain why it answers the command word. This helps A-Level Biology students avoid memorising one surface pattern.
Worked example 3: Mark-scheme check
Finish by checking the answer against marks: one point for the correct Inheritance & Selection idea, one for accurate working or evidence, and one for a precise final statement. If any step is vague, rewrite it before moving to timed practice.
Mini lesson for Inheritance & Selection
1. Understand the core idea
Inheritance is the process by which genetic information is passed on from parent to offspring. A-Level Biology explores Mendelian inheritance, including monohybrid and dihybrid crosses, codominance, and sex linkage.
Can you explain Inheritance & Selection without copying the notes?
2. Turn it into marks
In a monohybrid cross between two heterozygous parents (e.
Underline the method, evidence, or command-word move that would earn credit in A-Level Genetics & Evolution.
3. Fix the likely mark leak
Watch for this mistake: Confusing genotype and phenotype. Genotype is the genetic makeup of an organism (the combination of alleles), while phenotype is the observable characteristics resulting from the genotype and environmental factors.
Write one correction rule before doing another practice question.
Practise this topic
Start with low-focus cards for Inheritance & Selection, then move into full exam-style practice when you want the heavier session.
Mini quiz: Inheritance & Selection
Three quick checks for revision practice. They are original StudyVector prompts, not official exam-board questions.
Question 1
In one A-Level sentence, explain what Inheritance & Selection is testing.
Answer: Inheritance is the process by which genetic information is passed on from parent to offspring. A-Level Biology explores Mendelian inheritance, including monohybrid and dihybrid crosses, codominance, and sex linkage.
Mark focus: Precise definition and topic focus.
Question 2
A Inheritance & Selection question uses an unfamiliar context. What should the answer do before adding detail?
Answer: It should name the process, variable, equation, particle model, or evidence being tested, then explain the result using precise scientific vocabulary.
Mark focus: Method selection and command-word control.
Question 3
A student makes this mistake: "Confusing genotype and phenotype. Genotype is the genetic makeup of an organism (the combination of alleles), while phenotype is the observable characteristics resulting from the genotype and environmental factors." What should their next repair task be?
Answer: Do one Inheritance & Selection question and review the mistake type.
Mark focus: Error correction and next-step practice.
Inheritance & Selection flashcards
Core idea
What is the main idea in Inheritance & Selection?
Inheritance is the process by which genetic information is passed on from parent to offspring. A-Level Biology explores Mendelian inheritance, including monohybrid and dihybrid crosses, codominance, and sex linkage.
Common mistake
What mistake should you avoid in Inheritance & Selection?
Confusing genotype and phenotype. Genotype is the genetic makeup of an organism (the combination of alleles), while phenotype is the observable characteristics resulting from the genotype and environmental factors.
Practice
What is one useful practice task for Inheritance & Selection?
Answer one Inheritance & Selection question and review the mistake type.
Exam board
How should you use board notes for Inheritance & Selection?
All A-Level Biology boards (AQA, Edexcel, OCR) cover Mendelian genetics, natural selection, and speciation. The use of the chi-squared test to analyse genetic cross data is a key statistical skill required by all boards.
Common mistakes
- 1Confusing genotype and phenotype. Genotype is the genetic makeup of an organism (the combination of alleles), while phenotype is the observable characteristics resulting from the genotype and environmental factors.
- 2Incorrectly setting up Punnett squares for dihybrid crosses. A common error is not correctly determining all possible gamete combinations from the parental genotypes.
- 3Misunderstanding the different types of selection. Directional selection favours one extreme phenotype, stabilising selection favours the mean phenotype, and disruptive selection favours both extreme phenotypes.
Inheritance & Selection exam questions
Exam-style questions for Inheritance & Selection with mark-scheme style solutions and timing practice. Aligned to AQA, Edexcel, OCR, WJEC, Eduqas, CCEA, Cambridge International (CIE), Pearson Edexcel International, OxfordAQA International, SQA, IB, AP specifications.
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Step-by-step method
Step-by-step explanation
4 steps · Worked method for Inheritance & Selection
Core concept
Inheritance is the process by which genetic information is passed on from parent to offspring. A-Level Biology explores Mendelian inheritance, including monohybrid and dihybrid crosses, codominance, a…
Frequently asked questions
What is the difference between codominance and incomplete dominance?
In codominance, both alleles are fully expressed in the phenotype (e.g., AB blood type). In incomplete dominance, the heterozygous phenotype is an intermediate blend of the two homozygous phenotypes (e.g., a pink flower from red and white parents).
What is speciation?
Speciation is the evolutionary process by which new biological species arise. It often occurs when a population becomes reproductively isolated, leading to the accumulation of genetic differences over time through natural selection and genetic drift.