Germany Jahrgangsstufe 13 Biology
Chapters: 4
1. Biology: gaining, communicating, evaluating knowledge
Biology subject knowledge · Scientific inquiry in biology · Communicating biology · Evaluating bioethical issues
- The Scientific Method – The scientific method is the careful way scientists find out how the world works. Observe something, ask a testable question, make a hypothesis (a clear, testable guess), test it with a fair experiment (change one variable, measure one, keep the rest the same), repeat and record data, analyse it, draw a conclusion and share it so others can check. Results that fail the test are useful too: they send you back to a new hypothesis.
- Research Skills: From a Question to a Finished Project – Research is a careful way of finding an answer. You ask a clear, focused question, plan how to answer it, find information and check that each source can be trusted, collect and analyse your own data, draw a conclusion that the evidence supports, and share it while crediting every source you used.
- Bioethics: Deciding What Is Right in Biology and Medicine – Bioethics asks whether we should do what biology and medicine now let us do. It uses four principles: autonomy (respect choice), beneficence (do good), non-maleficence (do no harm) and justice (fairness). Human dignity means a person is never only a means to an end, so informed consent is needed. Therapeutic cloning may be allowed under strict rules; reproductive human cloning is banned in most countries. Start-of-life and end-of-life questions are weighed as benefits against risks and values.
2. Neural information processing
Neurons and nerve signals
- Neural Control and Coordination – Coordination means organs working together. The nervous system does this fast, using neurons. A neuron has a cell body, dendrites and an axon; many axons have a myelin sheath with nodes of Ranvier. The central nervous system (brain and spinal cord) processes information; the peripheral nervous system (nerves) carries it. The PNS has a somatic part (skeletal muscles) and an autonomic part (sympathetic and parasympathetic) for internal organs, the visceral system. At rest the axon is polarised: inside −, outside +, about −70 mV. A stimulus lets Na+ rush in, creating an action potential that travels along the axon. At a synapse, neurotransmitters carry the signal to the next neuron.
3. Cell metabolism physiology
Photosynthesis · Plant metabolism and enzymes · Fermentation and cellular respiration
- Photosynthesis in Higher Plants – Green plants make sugar from carbon dioxide and water using light. It happens in chloroplasts. The light reaction in the thylakoids splits water, gives out oxygen and makes ATP and NADPH. The Calvin cycle in the stroma uses that ATP and NADPH to fix CO₂ into sugar. C₄ plants add a CO₂ pump that stops the wasteful photorespiration. The slowest factor, such as light, CO₂ or temperature, sets the rate.
- Biomolecules – A cell is mostly water, plus four big families of carbon compounds: proteins, carbohydrates, lipids and nucleic acids. Grinding tissue in acid separates small molecules (acid-soluble pool) from big ones – proteins, polysaccharides and nucleic acids (acid-insoluble pool). Proteins are chains of amino acids folded into four levels of structure. Polysaccharides are chains of sugars; lipids are fatty acids on glycerol; nucleic acids are chains of nucleotides. Enzymes are protein catalysts that bind a substrate at the active site, lower the activation energy, and are affected by temperature, pH, substrate level and inhibitors.
- Respiration in Plants – Respiration breaks food like glucose to release energy stored as ATP. Plants take in O₂ through stomata and lenticels. Glycolysis in the cytoplasm splits glucose into two pyruvates. Without O₂, pyruvate is fermented to ethanol or lactic acid. With O₂, pyruvate enters the mitochondrion, runs the Krebs cycle, and the electron transport system uses O₂ to make most of the ATP: up to 38 per glucose. The same path also builds molecules (amphibolic). RQ = CO₂ given out ÷ O₂ taken in.
4. Ecology and biodiversity
Dynamic processes in ecosystems · Human impact and value of biodiversity · Ecology of the biosphere
- Ecosystem: Structure, Productivity, Energy Flow and Pyramids – An ecosystem is a working unit of nature where living things (biotic) and non-living things (abiotic) interact. Plants make food at a rate called productivity: gross (GPP) minus respiration gives net (NPP = GPP − R). Dead matter is broken down in five steps: fragmentation, leaching, catabolism, humification and mineralisation. Energy enters as sunlight, flows one way through trophic levels and only about 10% passes on each time. Ecological pyramids of number, biomass and energy show this; number and biomass pyramids can be inverted, but the energy pyramid is always upright.
- 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).