Biology, 14–17 years — 20 topics · MyLeoNes™ Kuks
20 biology topics written for 14–17 years — not a older text simplified. In teaching order, each a deck of five cards: the idea, why it exists, a worked example, the common trap and where you meet it.
Biology · 14–17 years
Cells: one living system, many specialised jobs
Living things are built from cells, but cells are not all alike. Their structures suit the jobs they perform, while shared features keep them alive.
DNA: instructions used to build proteins
DNA stores information in a sequence of bases. Cells read sections of that sequence to make proteins, linking inherited information with traits and cell activities.
Natural selection changes populations
Individuals vary, some differences are inherited, and resources are limited. When a heritable difference affects survival or reproduction, it can become more common over generations.
Energy flows through ecosystems
An ecosystem links organisms with the physical conditions around them. Energy enters mainly through sunlight, moves through feeding relationships and is gradually lost as heat.
Homeostasis: keeping conditions steady
Living things work best within narrow limits. Homeostasis is how cells and organs sense change and adjust the body, such as controlling temperature or blood glucose.
Enzymes: speeding up life’s chemistry
Cells contain countless chemical reactions, but many would be far too slow at body temperature. Enzymes make selected reactions faster by providing a suitable place for molecules to react.
Inheritance: how gene versions combine
Offspring receive genetic information from two parents, but not as a simple half-and-half copy. Different versions of a gene, called alleles, combine in patterns that help explain inherited traits and genetic disorders.
The immune response: recognising threats
The immune system must attack harmful invaders while limiting damage to the body’s own cells. It uses barriers, cells and molecules that recognise clues from pathogens and build targeted responses.
Photosynthesis: turning light into stored chemical energy
Photosynthesis explains how plants, algae and some bacteria use light to make glucose from carbon dioxide and water. It links sunlight, food and the oxygen in the air.
Cellular respiration: releasing usable energy from glucose
Cellular respiration is the controlled process that transfers energy from glucose to ATP, the cell’s convenient energy carrier. It explains how cells power movement, growth, active transport and repair.
Mitosis: making genetically matching cells
Mitosis is the cell-division process used for growth, repair and replacement. One parent cell copies its DNA and divides so that two daughter cells receive matching genetic information.
Meiosis: making sex cells with genetic variety
Meiosis makes sperm, eggs and other sex cells with half the usual chromosome number. It also reshuffles genetic material, so offspring receive combinations that are not identical to either parent.
Cell membranes control movement
A cell must exchange materials with its surroundings without losing control of what is inside. Diffusion, osmosis and active transport explain how substances cross its membrane.
Gene regulation: using the right instructions
Nearly every cell carries the same DNA, yet a nerve cell and a muscle cell behave differently. Gene regulation controls which instructions are read, when they are read and how strongly, allowing cells to specialise.
Vaccination builds immune memory
A vaccine gives the immune system a safe way to meet a target before the real disease arrives. The resulting memory can make a later response faster and stronger, reducing the chance of serious illness.
The nitrogen cycle
Nitrogen is needed to build proteins and DNA, but most atmospheric nitrogen cannot be used directly by plants. The nitrogen cycle moves it through air, soil, organisms and decomposers, making life possible while linking ecosystems to human activity.
Mutations: changes in genetic information
A mutation changes a DNA sequence. It may have no visible effect, or it may alter a protein and influence an organism’s traits or survival.
Genetic drift: chance changes in populations
Genetic drift changes how common gene versions are because of chance. It is strongest in small populations, where a few births, deaths, or migrants can have a large effect.
Speciation: how new species arise
A new species can arise when populations become separated and change until they can no longer successfully reproduce with one another.
The carbon cycle: matter moving through life and Earth
Carbon atoms move between the air, living things, soils, oceans, and rocks. Photosynthesis, respiration, decomposition, and combustion change where carbon is stored.
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