Biology is the science of life — of how living things are built, how they work, and how they relate to each other and their surroundings. This chapter sets up the ideas the whole course rests on.
1 · What makes something "living"?
Living organisms share a set of characteristics of life:
Organisation — built from one or more cells in an ordered way.
Nutrition — obtain food/energy (make it or take it in).
Respiration — release energy from food.
Growth & development — increase in size and complexity.
Reproduction — produce new individuals.
Response (irritability) — react to changes in the surroundings.
Excretion — remove metabolic wastes.
Movement — change position or move parts.
2 · Levels of biological organisation
Life is organised in a hierarchy, each level built from the one below:
From small to large atom → molecule → organelle → cell → tissue → organ → organ system → organism → population → community → ecosystem → biosphere.
Biology studies every level — from the molecules inside a cell to whole ecosystems.
3 · Branches of biology
The subject is huge, so it's divided into branches. Some by the group studied — zoology (animals), botany (plants), microbiology (microbes) — and some by the topic — genetics, ecology, physiology, anatomy, cell biology. Where biology overlaps other sciences we get biochemistry, biophysics and biotechnology.
4 · The scientific method
Biology is built on evidence. The scientific method is the cycle scientists use:
Observation — notice something and ask a question.
Hypothesis — a testable, tentative explanation.
Experiment — a fair test with controlled variables.
Results & analysis — collect and interpret data.
Conclusion — does the evidence support the hypothesis? Repeat & refine.
A hypothesis supported by lots of evidence over time may become a theory (a well-tested explanation) or a law (a consistent observed pattern).
Why a "fair test" matters
A good experiment changes one variable (the independent variable), measures its effect (the dependent variable), and keeps everything else the same (controlled variables) — plus a control for comparison. You'll use exactly this design in the practicals.
In one minute
Biology = the study of life; living things show organisation, nutrition, respiration, growth, reproduction, response, excretion, movement.
Levels: atom → cell → tissue → organ → organism → ecosystem → biosphere.