Biology as a Science: Methods and Signs of Life
Biology is the science of living nature. Its branches (botany, zoology, anatomy, physiology, ecology, genetics, microbiology) each study a different level or group of organisms, but they share common methods: observation, description, comparison, experiment, modelling and measurement. The scientific method runs in a fixed order: observation → hypothesis → experiment → conclusion → theory. A hypothesis is a testable assumption, not a proven fact; a theory is a broad explanation supported by many independent results.
Questions love to blur the difference between methods and results. Comparing a frog and a fish is comparison; growing plants under two light regimes is an experiment; a diagram of a food web is modelling. Another trap: distinguishing a property of life from a mere physical phenomenon. Living systems are characterised by metabolism, self-reproduction, heredity and variability, growth and development, irritability (excitability), self-regulation and adaptation to environment. A crystal grows but does not metabolise or reproduce, so growth alone does not prove life.
Rule of thumb
Ask: what was done (method) and what feature is shown (property of life). One sentence in the task usually names both, and the wrong options swap them.
Worked example
"A scientist placed two groups of bean seedlings in light and in darkness and measured their height for ten days." The method is experiment (a controlled test), and the property demonstrated is the influence of environment on growth, i.e. adaptation/development. An option calling this "observation only" is wrong because a variable was deliberately changed.