Continuity and Change: notes and practice questions
D. Continuity and change (SL 34 h, HL 60 h). The largest theme at both levels. Replication, protein synthesis and mutation; cell division, gene expression (HL only) and water potential; reproduction, inheritance and homeostasis; then natural selection, ecosystem stability and climate change. The hard parts are genetics (D3.2 carries the most calculation in the syllabus), the menstrual cycle hormones, and water potential sign conventions at HL. It is examined everywhere, and D3.2 Inheritance is the single most reliably examined subtopic in the course.
Subtopics
- Practice questionsDNA Replication
This topic covers the process of DNA replication, its semi-conservative nature, and its applications in biotechnology. DNA replication produces exact copies of DNA with identical base sequences, essential for reproduction, growth, and tissue replacement.
- Practice questionsReproduction
This topic covers the mechanisms and processes of reproduction in living organisms, focusing on both sexual and asexual strategies. Asexual reproduction produces genetically identical offspring, while sexual reproduction generates variation through meiosis and gamete fusion.
- Practice questionsInheritance
This topic covers the mechanisms of heredity, including how genetic information is passed from parents to offspring and the factors influencing trait expression. Sexual reproduction involves haploid gametes fusing to form a diploid zygote.
- Practice questionsHomeostasis
This topic covers the maintenance of constant internal conditions in organisms, known as homeostasis. Homeostatic variables include body temperature, blood pH, blood glucose concentration, and blood osmotic concentration.
- Practice questionsNatural Selection
This topic covers natural selection as the mechanism for evolutionary change, driven by heritable characteristics within a population. Variation arises from mutation, generating new alleles, and sexual reproduction, creating new combinations of alleles.
- Practice questionsSustainability and Change
This topic examines ecosystem stability, human impacts on biodiversity, and climate change. Ecosystem stability relies on energy flow, nutrient cycling, genetic diversity, and stable climatic variables.
- Practice questionsClimate Change
This topic explores the anthropogenic drivers and ecological impacts of climate change on ecosystems. Anthropogenic causes include increased atmospheric concentrations of carbon dioxide and methane.
- Practice questionsProtein Synthesis
This topic covers the processes of transcription and translation, which together synthesize proteins from a DNA template. Transcription involves RNA polymerase synthesizing messenger RNA (mRNA) from a DNA template, with adenine (A) on DNA pairing with uracil (U) on RNA.
- Practice questionsMutations and Gene Editing
This topic covers the molecular basis of gene mutations and their role in genetic variation and disease. Gene mutations are structural changes at the molecular level, including substitutions, insertions, and deletions.
- Practice questionsCell and Nuclear Division
This topic covers cell division (mitosis and meiosis) for growth, repair, and reproduction. Cell division involves nuclear division followed by cytokinesis.
- Practice questionsWater Potential
This topic covers the movement of water into and out of cells by osmosis and its consequences for living organisms. Water acts as a solvent due to hydrogen bonding and attractions to polar or charged molecules.
- Practice questionsGene ExpressionHL only
This topic explores the mechanisms by which genetic information is expressed and regulated in cells. Gene expression involves transcription (DNA to RNA), translation (RNA to protein), and the function of the protein product.
