France Terminale Scientific Education
Chapters: 3
1. Science, climate and society
Atmosphere and life · The climate system · Future climate · Energy choices and climate
- Composition and Structure of the Atmosphere – The atmosphere is a thick blanket of air held to the Earth by gravity. It is mostly nitrogen (78%) and oxygen (21%), with small amounts of argon, carbon dioxide, ozone, water vapour and dust. It has five layers: troposphere (where weather happens), stratosphere (ozone layer), mesosphere (coldest), thermosphere (ionosphere, very hot) and exosphere (the outer edge). Weather is the state of air for a short time; climate is the average over about 30 years. Both are described by the same elements: temperature, pressure, wind, humidity, clouds and precipitation.
- Climate Change and the Greenhouse Effect – Climate is the average weather of a place over about 30 years. Greenhouse gases like carbon dioxide and methane trap some of the heat the Earth gives off. Humans have added a lot more of these gases by burning fossil fuels and cutting forests, so the Earth is warming. This causes melting ice, rising seas and more extreme weather. We can cut emissions (mitigation) and prepare for changes (adaptation).
- Minerals and Energy Resources – Minerals are natural substances found in rocks. They are metallic (ferrous or non-ferrous), non-metallic, or energy minerals. Energy comes from conventional sources like coal, petroleum, natural gas and electricity, and from non-conventional sources like sun, wind, nuclear, biogas, tides and heat from the Earth. Both minerals and energy must be conserved.
2. The future of energy
Two centuries of electricity · Advantages of electricity · Optimising electricity transmission · Energy choices and society
- How Electricity Is Generated – Most electricity is made by spinning a magnet inside coils of wire (or coils near magnets). This is electromagnetic induction, and the machine is an alternator. A turbine does the spinning; steam, water or wind turns the turbine. Solar cells are different: light makes current directly. Transformers raise the voltage so the grid can carry power far with little loss.
- Electric Power and Electrical Energy – Electric power is the rate of using electrical energy: P = VI = I²R = V²/R, in watts. Energy used = power × time. At home energy is measured in kilowatt-hours: 1 kWh = 1 unit = 3.6 × 10⁶ J. Bill = units × rate.
- Power Grid and High-Voltage Transmission – A power line wastes energy as heat: loss = I²R. For a fixed power P = V × I, raising the voltage lowers the current, so the loss falls with the square of the voltage. Transformers step the voltage up at the power station and down near homes. The grid is a network of lines (a graph) with many routes, so supply continues if one line fails.
- Minerals and Energy Resources – Minerals are natural substances found in rocks. They are metallic (ferrous or non-ferrous), non-metallic, or energy minerals. Energy comes from conventional sources like coal, petroleum, natural gas and electricity, and from non-conventional sources like sun, wind, nuclear, biogas, tides and heat from the Earth. Both minerals and energy must be conserved.
3. A history of life
Biodiversity and its change · Evolution as a way to read the world · Human evolution · Population models · Artificial intelligence
- Biodiversity and its Conservation – Biodiversity is the variety of life at three levels: genetic, species and ecological. It is highest near the equator and grows with area (log S = log C + Z log A). Every species matters, like rivets on a plane. We are losing species fast because of the 'evil quartet': habitat loss and fragmentation, over-exploitation, alien species invasions and co-extinction. The IUCN Red List (Red Data Book) ranks species from Least Concern to Extinct. We protect life in situ (hotspots, national parks, sanctuaries, biosphere reserves, sacred groves, Ramsar wetlands) and ex situ (zoos, botanical gardens, seed and gene banks).
- Diversity and Classification of Living Organisms – Earth has millions of kinds of living things, and India is one of the richest places. To study them, we sort them into groups by asking simple questions about their bodies: Is there a nucleus? One cell or many? Can it make its own food? This gives five kingdoms: Monera, Protista, Fungi, Plantae and Animalia. Animals split into invertebrates and vertebrates. Every species gets a two-part scientific name. Viruses are not cells, so they fit in no kingdom.
- Evolution: How New Kinds of Living Things Arise – Variations arise during reproduction. Nature selects those that help survival, so over many generations populations change: this is evolution. Only inherited (DNA) changes pass on; acquired changes do not. Separated populations can become new species. Homologous organs, analogous organs and fossils help us trace who is related to whom, and complex organs evolved step by step.
- Evolution: Origin of Life, Mechanisms and Human Evolution – Life began on the early Earth from simple chemicals: Oparin and Haldane proposed it and Miller made amino acids in a flask. Evidence of evolution comes from fossils, homologous and analogous organs, embryos, molecules and changes we can watch (industrial melanism, drug resistance). Darwin explained it by natural selection acting on variation in populations; the modern synthetic theory adds genes: mutation, recombination, gene flow, genetic drift and natural selection change allele frequencies. If none of these act, frequencies stay constant: Hardy–Weinberg, p² + 2pq + q² = 1. Selection can be stabilising, directional or disruptive. One ancestor spreading into many habitats gives adaptive radiation (Darwin’s finches, Australian marsupials). Humans evolved from Dryopithecus-like apes through Australopithecus, Homo habilis, Homo erectus and Neanderthals to Homo sapiens.
- Organisms and Populations: Growth and Interactions – A population is a group of the same species living in one area at one time. It has features that a single organism does not have: density, birth rate, death rate, sex ratio and age structure. N grows by births and immigration and shrinks by deaths and emigration. With unlimited food it grows fast (J-curve, dN/dt = rN); with limited food it slows and stops at the carrying capacity K (S-curve, dN/dt = rN(1 − N/K)). Different species affect each other: mutualism (+/+), competition (−/−), predation and parasitism (+/−), commensalism (+/0) and amensalism (−/0).
- Artificial Intelligence: How Machines Learn to Think – Artificial intelligence (AI) is the skill of a computer system to do tasks that normally need human thinking: seeing, understanding speech, deciding and learning. An AI system is an agent that senses, thinks and acts. Old AI followed rules written by people. Modern AI mostly uses machine learning: it finds its own rule from many labelled examples (data). Neural networks are layers of simple units whose link strengths (weights) change during training. AI is used in maps, translation, health, farming and games. It can be wrong or unfair when its data is one-sided (bias), so people must check it, protect privacy and stay responsible.