Zadanie 6, Paper 2, maj 2022, TZ1, Biologia IB HL

(a) Hydrogen bonds attract neighbouring water molecules. ✔

Energy is needed to overcome those attractions during evaporation. ✔

Water has a high latent heat of vaporization. ✔

Evaporating water removes heat from the skin. ✔

(b) Transpiration releases water vapour through stomata. ✔

Water loss from leaves drives water movement in xylem. ✔

Higher temperature generally increases water loss and transport. ✔

Heat supplies energy for evaporation. ✔

Higher humidity reduces the outward water-vapour gradient and slows loss. ✔

Low humidity promotes diffusion of water vapour out of leaves OR at equal leaf/air temperature saturated air prevents net evaporation. ✔

Air movement usually increases loss. ✔

Wind removes the moist boundary layer around a leaf. ✔

Very strong wind can induce stomatal closure and reduce loss. ✔

Drought induces stomatal closure, reducing water loss and transport. ✔

(c) Dehydration can stimulate thirst. ✔

Drinking increases water intake OR increased water recovery from faeces reduces loss. ✔

Hypothalamic osmoreceptors detect increased blood solute concentration. ✔

ADH secretion increases. ✔

The pituitary gland releases ADH; posterior localization is optional. ✔

Collecting-duct cells OR cells of the ADH-sensitive late distal tubule become more permeable to water. ✔

More aquaporins are inserted into the plasma membranes of these cells. ✔

More water is reabsorbed from the filtrate in collecting ducts or ADH-sensitive distal segments. ✔

Reabsorption occurs by osmosis OR is favoured by the hypertonic medulla. ✔

Reabsorbed water returns to blood OR reduces blood solute concentration. ✔

Urine volume falls OR urine becomes more concentrated. ✔

Reduced sweating can limit further water loss. ✔

Quality: the response is clear on first reading, concise and contains little repetition or irrelevant material. ✔

Part (a): any 3 points, maximum 3. Part (b): any 5 points, maximum 5. Part (c): any 7 points, maximum 7. Award 1 independent quality mark for the stated communication criterion. Total maximum 16. Accept scientifically valid equivalent wording and alternatives; do not require every listed point.