Biology

Every living thing runs on chemistry. In this unit you will learn the molecules of life and the reactions that build and break them, then see how cells use enzymes and membranes to control which reactions happen, where, and how fast.

What you will learn:

• How organelles, especially the endomembrane system, cooperate to make, package and ship molecules.
• The bonds, intermolecular attractions and functional groups that give biological molecules their properties, and the four key reaction types: condensation, hydrolysis, neutralization and redox.
• The structure and function of carbohydrates, lipids, proteins and nucleic acids (including ATP), and how to identify them in foods with chemical tests.
• How enzymes lower activation energy, how cofactors and inhibitors affect them, and how cells regulate them with allosteric sites and feedback inhibition. You will plan and analyse your own enzyme investigation.
• The fluid mosaic model of the cell membrane, and how materials cross it by diffusion, osmosis, facilitated diffusion, active transport, endocytosis and exocytosis.
• How enzymes are used in the food, pharmaceutical and other industries, and how to evaluate advances in cellular biology such as targeted cancer drugs, HIV and hepatitis C treatments, radioisotope labelling, fluorescence and forensic DNA profiling, along with related careers and Canadian contributions.

What it builds on: cell organelles from Grade 10 Science (SNC2D); nutrient tests and enzyme basics from Grade 11 Biology (SBI3U); and bonding, polarity and electronegativity from Grade 11 Chemistry (SCH3U).

Where it leads: this unit is the foundation for the rest of the course. Metabolic Processes follows energy through cellular respiration and photosynthesis using the enzymes, redox reactions and membranes you meet here. Molecular Genetics builds on nucleotides and DNA structure. Homeostasis depends on membrane transport, hormones and feedback. Population Dynamics applies the same evidence-and-evaluation skills to populations and ecosystems.

Many lessons include safe hands-on activities with household materials. All home activities avoid hazardous chemicals; the full laboratory tests are described for you to analyse rather than perform at home.

Every second, each of your cells makes and uses millions of ATP molecules, and every leaf outside your window is turning sunlight, water and CO₂ into sugar. In this unit you will follow energy and matter through living things at the level of molecules: how cells harvest energy from food, how plants capture energy from light, and how these two processes shape your health, Ontario's lakes and the planet's atmosphere.

What you will learn

• How the laws of thermodynamics, free energy (ΔG) and enzymes apply to living things (Lesson 1).
• How ATP stores and transfers energy, and how cells couple reactions (Lesson 2).
• Oxidation and reduction and the electron carriers NAD⁺, FAD and NADP⁺ (Lesson 3).
• The stages of cellular respiration: glycolysis, pyruvate oxidation, the Krebs cycle, and the electron transport chain with chemiosmosis, plus ATP totals, other fuels and how the pathway is controlled (Lessons 4 to 7).
• Fermentation and anaerobic respiration, and how to investigate the products of respiration (Lessons 8 and 9).
• How metabolism connects to exercise, training and diet (Lesson 10).
• Photosynthesis: chloroplasts and pigments, the light-dependent reactions, the Calvin cycle, photorespiration, and C₄ and CAM plants, and how to investigate the products of photosynthesis (Lessons 11 to 14).
• How respiration and photosynthesis compare and connect (matter cycles, energy flows) (Lesson 15).
• How metabolic processes link living things with the atmosphere, water and soil, including the carbon cycle, eutrophication and technologies such as fermentation, biofuels, anaerobic digestion and wastewater treatment (Lesson 16).

Building on earlier grades: In Grade 9 Science you met the word equations for photosynthesis and cellular respiration and the roles of chloroplasts and mitochondria. In Grade 11 Biology (Plants: Anatomy, Growth, and Function) you studied leaves, stomata and how sugar moves through a plant. This unit takes those ideas down to the level of enzymes, electrons and protons. It builds directly on the Biochemistry unit (enzymes, macromolecules and membranes), and it connects to Homeostasis (blood sugar and temperature control), Molecular Genetics (the genes for these enzymes) and Population Dynamics (how populations grow and interact in ecosystems).

You will need: everyday kitchen items (red cabbage, dry baker's yeast, sugar, balloons, baking soda, dish soap, spinach leaves, an apple and a lemon), clear glasses or jars, drinking straws, a 10 mL needle-free syringe, a desk lamp, a thermometer, a stopwatch and a notebook. Lesson 11 uses rubbing alcohol (flammable; used in a ventilated room away from flames). Activities with knives, heat, flammable liquids or small objects include a safety note. School labs may use bromothymol blue, limewater, iodine and respirometers; every investigation gives a safe home alternative.

How does a molecule made of just four kinds of building blocks store the instructions for a whole organism, copy them almost perfectly, and turn them into thousands of different proteins? And now that we can read and edit those instructions, what should we do with that power?

You begin with the experiments that identified DNA as the genetic material, from Griffith and Avery to Hershey and Chase, Chargaff, Franklin, and Watson and Crick, and the structure of DNA and RNA. You extract DNA yourself, then follow DNA replication at the fork (helicase, primase, DNA polymerases, Okazaki fragments, ligase) and the proofreading and repair systems that keep errors rare. Next comes gene expression: transcription, eukaryotic RNA processing (cap, tail and splicing), the genetic code and reading frames, and translation at the ribosome. You see how cells switch genes on and off, with the lac and trp operons in bacteria and chromatin, transcription factors and small RNAs in eukaryotes, and how mutations and mutagens change DNA.

The last part of the unit is biotechnology: restriction enzymes, plasmids and recombinant DNA; PCR, gel electrophoresis and DNA sequencing; genetic modification in industry and agriculture, cloning and CRISPR gene editing; and the social, ethical, legal and environmental questions these raise, along with careers in the field.

Remember from Grade 11: in Genetic Processes (SBI3U) you learned about meiosis, Mendelian inheritance, basic DNA structure, mutation types and an introduction to genetic technologies. This unit explains the molecular machinery behind all of that. It builds on the nucleotides, proteins and enzymes from Biochemistry, and links to Metabolic Processes (enzymes and ATP), Homeostasis (hormones that act by switching genes on) and Population Dynamics (genetic variation in populations).

Home activities use only kitchen materials. Where rubbing alcohol is used, an adult handles it and the room is ventilated; laboratory procedures that need hazardous chemicals are described for you to analyse, not to perform at home.

Curriculum: The Ontario Curriculum, Grades 11 and 12: Science (2008), Biology, Grade 12, University Preparation (SBI4U), strand D. Molecular Genetics: D1 (relating science to technology, society and the environment), D2.1 to D2.4 (developing skills of investigation and communication) and D3.1 to D3.7 (understanding basic concepts). Strand A (Scientific Investigation Skills and Career Exploration) is woven through the lessons. Every lesson has worked examples, a hands-on activity, lots of practice and a short quiz.

How does your body stay at about 37 °C on a −30 °C January morning and on a +35 °C July afternoon? Why is your urine pale one day and dark the next? How does a single molecule of a hormone change what millions of cells are doing, and how does a nerve signal cross the gap between two neurons? This unit answers these questions with the big idea of homeostasis: keeping the body's internal environment steady by feedback.

You will start with feedback loops and thermoregulation. Then you will study the excretory system: the nephron, water and ion balance (ADH, aldosterone and blood pressure), acid–base balance, and kidney disorders, dialysis and transplants. Next comes the endocrine system: how hormones act, blood glucose and diabetes (including the Canadian discovery of insulin), stress, thyroid and growth hormones, and reproductive hormones. You will explore the nervous system: its organization and reflexes, the action potential and synapses. You will design an investigation of how invertebrates respond to stimuli, and finish by evaluating the effects of chemical substances, environmental factors linked to human activity, and medical technologies on homeostasis, along with related careers.

This unit covers Strand E (Homeostasis) of the Ontario Grade 12 Biology, University Preparation course (SBI4U, The Ontario Curriculum, Grades 11 and 12: Science, 2008), with the scientific investigation skills and career exploration of Strand A woven throughout. It builds on Grade 10 Tissues, Organs, and Systems (SNC2D) and Grade 11 Animals: Structure and Function (SBI3U), and connects to the other SBI4U units: Biochemistry, Metabolic Processes, Molecular Genetics and Population Dynamics.

Why do snowshoe hares boom and crash about every ten years? How many fish can be caught each year without emptying a lake? How many people can Earth support, and how big is your share of the planet? In this unit you will answer questions like these with the same tools that ecologists, wildlife managers, fisheries scientists and demographers use.

You will start by describing populations: size, density (crude and ecological), dispersion (clumped, uniform and random, tested with the variance-to-mean ratio), age structure and minimum viable population. You will estimate populations with quadrats, transects and mark-recapture (Lincoln-Petersen and Chapman), build life tables, calculate the net reproductive rate R₀, and interpret Type I, II and III survivorship curves, using the terms fecundity, mortality and carrying capacity precisely.

Next you will model growth: ΔN = (b + i) − (d + e), geometric growth (Nₜ = N₀λᵗ), exponential growth (Nₜ = N₀eʳᵗ, doubling time) and logistic growth with carrying capacity (dN/dt = rN(K − N)/K). You will explain what limits populations (density-dependent and density-independent factors, Liebig's and Shelford's laws, the Experimental Lakes Area), compare r- and K-selected life histories, and study how species interact: competition (Gause, Connell, MacArthur's warblers), predation and defence mechanisms (camouflage, warning colours, Batesian and Müllerian mimicry, keystone sea otters) and symbiosis (mutualism, commensalism, parasitism). In an investigation you will run predator-prey and host-parasitoid simulations in a spreadsheet and compare them with laboratory and field results such as the snowshoe hare-lynx cycle.

Finally you will apply everything to people: human population growth and the demographic transition (with 2026 figures), consumption, technology and the ecological footprint (a Canadian invention), Canadian technologies and projects intended to nourish growing populations, and sustainable management, including the lessons of the northern cod collapse and the contributions of First Nations, Métis and Inuit knowledge and co-management. You will also meet careers that use these ideas.

Remember from earlier grades: Grade 9 (Sustainable Ecosystems and Climate Change) introduced carrying capacity, limiting factors and the lynx-hare cycle; Grade 11 Diversity of Living Things taught quadrats, transects and Lincoln-Petersen mark-recapture; Grade 11 Evolution taught natural selection, niches and Malthus. This unit makes those ideas quantitative. A scientific calculator with ln and eˣ keys and a free spreadsheet program are all you need. If you are taking Advanced Functions (MHF4U), you will recognize its exponential and logarithmic functions throughout.

Other units in this course: Biochemistry, Metabolic Processes, Molecular Genetics and Homeostasis. Population Dynamics links most closely to Metabolic Processes (energy flow that sets carrying capacity) and Molecular Genetics (biotechnology in agriculture).

Curriculum: The Ontario Curriculum, Grades 11 and 12: Science (2008, revised), Biology, Grade 12, University Preparation (SBI4U), strand F. Population Dynamics: overall expectations F1 (relationships among population growth, consumption, technology and ecological footprint; Canadian initiatives), F2 (investigating population growth with models) and F3 (concepts of population growth and the factors that affect it), specific expectations F1.1 to F3.3. Strand A (Scientific Investigation Skills and Career Exploration) is woven through the lessons and tagged where a lesson clearly teaches it. Every lesson has worked examples, a hands-on activity, plenty of practice with full answers and a short quiz.