Biology,
one step at a time.

Smooth versus toothed edges are objective, visible and mutually exclusive. Subjective judgements such as attractive or useful make a key unreliable.

Watch for: Do not name a biological process without explaining the mechanism. For Characteristics and classification of living organisms, link the relevant structure or condition to the resulting effect.

Bacteria contain circular DNA that is not enclosed in a nucleus. Animal cells also contain membranes, cytoplasm and ribosomes.

Watch for: Do not name a biological process without explaining the mechanism. For Organisation of the organism, link the relevant structure or condition to the resulting effect.

A steeper concentration gradient increases net particle movement; larger area, higher temperature and shorter distance also increase diffusion rate.

Watch for: Do not name a biological process without explaining the mechanism. For Movement into and out of cells, link the relevant structure or condition to the resulting effect.

A colour control containing the same food but no Benedict's reagent reveals the sample's background appearance, helping interpretation of the test result.

Watch for: Do not name a biological process without explaining the mechanism. For Biological molecules, link the relevant structure or condition to the resulting effect.

Controlling concentrations prevents changes in collision frequency caused by different particle numbers from confounding the temperature effect.

Watch for: Do not name a biological process without explaining the mechanism. For Enzymes, link the relevant structure or condition to the resulting effect.

Destarching removes pre-existing starch, so starch found after controlled light exposure can be attributed to photosynthesis during the investigation.

Watch for: Do not name a biological process without explaining the mechanism. For Plant nutrition, link the relevant structure or condition to the resulting effect.

Fatty acids lower pH as lipase digests fat. A fixed colour endpoint, constant temperature and equal concentrations allow a fair rate comparison.

Watch for: Do not name a biological process without explaining the mechanism. For Human nutrition, link the relevant structure or condition to the resulting effect.

Wind carries away water vapour from the leaf boundary layer, preserving a steep diffusion gradient from air spaces to the atmosphere.

Watch for: Do not name a biological process without explaining the mechanism. For Transport in plants, link the relevant structure or condition to the resulting effect.

Systemic circulation has greater resistance and distance than pulmonary circulation, so the left ventricle needs more muscle to produce higher pressure.

Watch for: Do not name a biological process without explaining the mechanism. For Transport in animals, link the relevant structure or condition to the resulting effect.

Matched agar plates and controlled incubation allow microbial transfer to be compared without deliberate infection; plates should remain sealed after incubation.

Watch for: Do not name a biological process without explaining the mechanism. For Diseases and immunity, link the relevant structure or condition to the resulting effect.

Equal sample and reagent volumes make cloudiness a fair indicator; expired air should turn limewater milky more quickly because it contains more carbon dioxide.

Watch for: Do not name a biological process without explaining the mechanism. For Gas exchange in humans, link the relevant structure or condition to the resulting effect.

Continued circulation transports lactic acid from muscles to the liver, while extra oxygen supports its aerobic respiration and repays the oxygen debt.

Watch for: Do not name a biological process without explaining the mechanism. For Respiration, link the relevant structure or condition to the resulting effect.

Blood entering through the renal artery is filtered; lower urea concentration in the renal vein is evidence of renal excretion.

Watch for: Do not name a biological process without explaining the mechanism. For Excretion in humans, link the relevant structure or condition to the resulting effect.

Directional light is the independent variable; matched seedlings, controlled water and a uniform-light control test whether shoots bend towards light.

Watch for: Do not name a biological process without explaining the mechanism. For Coordination and response, link the relevant structure or condition to the resulting effect.

Symptoms can improve before all susceptible bacteria are eliminated; survivors can multiply, and selection may favour more resistant individuals.

Watch for: Do not name a biological process without explaining the mechanism. For Drugs, link the relevant structure or condition to the resulting effect.

Dissolved nutrients, oxygen and wastes diffuse between close circulations across placental tissue while the blood itself normally does not mix.

Watch for: Do not name a biological process without explaining the mechanism. For Reproduction, link the relevant structure or condition to the resulting effect.

After exact chromosome replication, mitosis separates copies into genetically identical daughter nuclei and maintains chromosome number.

Watch for: Do not name a biological process without explaining the mechanism. For Inheritance, link the relevant structure or condition to the resulting effect.

Environmental pressures cause differential survival and reproduction, increasing advantageous allele frequencies over generations.

Watch for: Do not name a biological process without explaining the mechanism. For Variation and selection, link the relevant structure or condition to the resulting effect.

Photosynthesis fixes atmospheric carbon dioxide into organic compounds; respiration, combustion and decomposition release it.

Watch for: Do not name a biological process without explaining the mechanism. For Organisms and their environment, link the relevant structure or condition to the resulting effect.

A spatial series with an upstream baseline, consistent technique and repeats can reveal whether nitrate concentration changes near the source.

Watch for: Do not name a biological process without explaining the mechanism. For Human influences on ecosystems, link the relevant structure or condition to the resulting effect.

Expression of the inserted gene can reduce feeding damage and may lower the need for chemical insecticides, though wider impacts still require evaluation.

Watch for: Do not name a biological process without explaining the mechanism. For Biotechnology and genetic modification, link the relevant structure or condition to the resulting effect.