Germany Jahrgangsstufe 10 Biology

Chapters: 4

1. Gaining, communicating and evaluating knowledge

Scientific inquiry and communication in biology

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.

2. The human body as ecosystem

The human body as an ecosystem

Infectious Diseases: How Germs Spread and How We Stop Them – An infectious (communicable) disease is caused by a tiny living thing called a pathogen: a bacterium, virus, fungus or protist. It passes from one person to another through air, water and food, touch, or a vector such as a mosquito. The body fights back with skin, mucus, stomach acid and white blood cells. Vaccines train the immune system in advance. Hand washing, clean water, cooking food well, mosquito nets and staying home when sick all cut the spread.

3. Metabolism and energy in humans

Biomolecules as energy stores and building blocks · Digestion and enzymes · Gas exchange and blood circulation · Energy supply by metabolism

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.
Human Digestive System and Heterotrophic Nutrition – Heterotrophs take ready-made food from other living things. Humans are holozoic: we eat whole food and break it down in a long tube, the alimentary canal. Teeth, saliva, stomach acid, enzymes, bile and pancreatic juice cut big food molecules into small ones that villi in the small intestine absorb into blood.
Transportation in Humans: Heart, Blood Vessels, Blood and Lymph – The heart is a four-chambered muscular pump. Blood passes through it twice in one full round: once to the lungs to pick up oxygen, and once to the rest of the body. This is double circulation. Arteries carry blood away from the heart, veins bring it back and capillaries do the exchange. Blood (plasma, RBCs, WBCs, platelets) and lymph together carry food, gases, hormones and wastes.
Respiration: Aerobic, Anaerobic and the Human Lungs – Respiration is the breakdown of food, usually glucose, inside cells to release energy, stored as ATP. With oxygen (aerobic) glucose is fully broken into carbon dioxide and water and gives much energy; without oxygen (anaerobic) it gives little energy and makes ethanol (yeast) or lactic acid (muscles). Our lungs bring oxygen to the blood through millions of alveoli.

4. Human past and future

Past and future of humankind

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.