B5: Genes, inheritance and selection – GCSE OCR Foundation Biology revision notes

What this topic covers

B5: Genes, inheritance and selection has 2 subtopics:

• B5.1 Inheritance
• B5.2 Natural selection and evolution

B5: Genes, inheritance and selection lessons by subtopic

34 lessons, grouped by subtopic.

B5.1 Inheritance

• Chromosomes, DNA and Genes: Understanding the structure and organisation of genetic material in cells, including how DNA is organised into chromosomes and the relationship between chromosomes, genes and their location in body cells.
• Gametes in Sexual Reproduction: Explore the specialized reproductive cells in animals and flowering plants, understanding how sperm, egg, and pollen cells enable sexual reproduction through the fusion of male and female gametes.
• Sexual vs Asexual Reproduction and Cell Division: Compare sexual and asexual reproduction, examining how meiosis creates genetic variety in sexual reproduction while mitosis produces identical clones in asexual reproduction, and understand the genetic consequences of each reproductive strategy.
• What is Meiosis?: Understand how meiosis produces gametes with half the number of chromosomes through two divisions, creating genetically different cells in reproductive organs.
• Fertilisation and Development: Learn how meiosis halves chromosome number in gametes, fertilisation restores the full number, and how the new cell develops through mitosis and differentiation.
• DNA Structure and the Genome: Learn about the structure of DNA as a double helix polymer, how genes code for proteins, and understand what the genome is and its importance for medicine.
• Applications of Genome Research: Explore how understanding the human genome is used to search for disease genes, understand inherited disorders, and trace human migration patterns throughout history.
• Genetic vocabulary and basic inheritance (Part 1/2): Learn key genetic terms including gamete, chromosome, gene, allele, dominant, recessive, homozygous, heterozygous, genotype and phenotype. Understand how alleles control characteristics and the difference between dominant and recessive alleles.
• Genetic vocabulary and basic inheritance (Part 2/2): Learn key genetic terms including gamete, chromosome, gene, allele, dominant, recessive, homozygous, heterozygous, genotype and phenotype. Understand how alleles control characteristics and the difference between dominant and recessive alleles.
• Genetic crosses and Punnett squares: Explore single gene inheritance using examples like fur colour in mice and colour blindness. Learn to construct and interpret Punnett squares, understand probability in genetic crosses, and use ratios to predict outcomes.
• Multiple gene inheritance: Understand that most characteristics are controlled by multiple genes rather than single genes, and appreciate the complexity of real inheritance patterns compared to simple single gene crosses.
• Understanding Inherited Disorders: Explore how genetic disorders are passed from parents to offspring, including the difference between dominant and recessive inheritance patterns using polydactyly and cystic fibrosis as examples.
• Ethical Issues in Embryo Screening: Examine the economic, social and ethical considerations surrounding embryo screening for inherited disorders, developing skills to make informed judgements on these complex issues.
• Sex Chromosomes and Genetic Crosses: Students learn about human sex chromosomes (XX for females, XY for males), the 23 pairs of chromosomes in human cells including the sex-determining pair, and how to carry out genetic crosses to show sex inheritance using ratios and proportions.
• Causes of Variation: Explore how genetic factors, environmental conditions, and their combination create variation in organisms. Learn about genetic diversity in populations and how the genome interacts with environment to determine phenotype.
• Mutations and Phenotype Changes: Understand how mutations continuously occur and their effects on phenotype. Discover how rare beneficial mutations can lead to rapid evolutionary changes when they suit environmental conditions.

B5.2 Natural selection and evolution

• What is Evolution?: Understanding evolution as changes in inherited characteristics over time and how all species evolved from simple life forms through natural selection.
• How Evolution Works Through Natural Selection: Exploring the mechanism of natural selection and how it leads to evolution by selecting variants with advantageous phenotypes for their environment.
• Formation of New Species: Understanding how populations become so different that they can no longer interbreed to produce fertile offspring, resulting in the formation of new species.
• What is Selective Breeding and How Does it Work?: Understand the process of selective breeding and learn about examples including disease-resistant crops, high-yield animals, gentle dogs, and decorative flowers.
• The Impact and Problems of Selective Breeding: Explore the benefits and drawbacks of selective breeding, including its impact on food production and the problems of inbreeding in domesticated animals.
• Darwin and Wallace: Developing the Theory of Evolution: Explore how Charles Darwin and Alfred Russell Wallace independently developed the theory of evolution by natural selection, their collaboration in 1858, and the publication of On the Origin of Species in 1859.
• Wallace's Contributions and the Impact on Biology: Investigate Alfred Wallace's worldwide evidence gathering, his work on warning colouration and speciation theory, and examine how evolutionary ideas transformed the field of biology.
• The Process of Speciation: Learn the step-by-step process that leads to the formation of new species, building on the foundational work of Wallace and modern understanding of speciation mechanisms.
• Evidence for Evolution: Explore the key evidence that supports the theory of evolution, including fossil records and antibiotic resistance in bacteria. Learn how these examples demonstrate evolutionary processes in action.
• Darwin's Theory and Modern Evidence: Understand how Darwin's theory of evolution by natural selection became widely accepted and examine the modern evidence that supports it, including genetic inheritance and bacterial resistance.
• What are fossils and how are they formed?: Students learn what fossils are and explore the three main ways fossils can form: from parts that haven't decayed, through mineral replacement, and as preserved traces like footprints and burrows.
• Fossils as evidence for evolution: Students discover why the fossil record is incomplete due to soft-bodied organisms and geological activity, and learn how fossils provide evidence for evolutionary change over time, including interpreting evolutionary trees and data.
• Understanding Extinction and Its Causes: Students will learn what extinction means and explore the various factors that can lead to species becoming extinct, including environmental changes, human activities, and natural disasters.
• How Antibiotic Resistance Develops: Learn how bacterial evolution and mutations lead to antibiotic-resistant strains, including the role of rapid reproduction and natural selection in creating superbugs like MRSA.
• Preventing Antibiotic Resistance: Explore strategies to reduce antibiotic resistance including appropriate prescribing by doctors, completing antibiotic courses, and restricting agricultural use, plus the challenges of developing new antibiotics.
• The Three-Domain System: Explore the modern three-domain classification system developed by Carl Woese, covering Archaea (primitive bacteria in extreme environments), Bacteria (true bacteria), and Eukaryota (including protists, fungi, plants and animals). Understand how advances in microscopy and biochemistry led to this new classification model.
• The Linnaean Classification System: Learn about Carl Linnaeus's traditional classification system using seven hierarchical levels: kingdom, phylum, class, order, family, genus and species. Understand the binomial naming system and practice using the Linnaean system to classify organisms.
• Evolution of Classification and Evolutionary Trees: Examine how biological developments have impacted classification systems over time and discover how scientists use evolutionary trees to show relationships between organisms using current classification data and fossil evidence.

More in this course

Go back to the full GCSE OCR Foundation Biology topic list, or practise this topic with past-paper questions.