10 a) was a pretty decent essay question I thought.
I discussed the following
INTERNAL:
Regulation of blood glucose concentration - insulin/glucagon - type II diabetes
Thermoregulation in endotherms - Heat loss/gain centre in hypothalamus, also threw in a bit about oxidation of brown fat for thermogenesis - otherwise hyper/hypothermia - denaturation of enzymes etc.
Blood pH/CO2 changes during exercise and effect on Heart Rate
Osmolarity of blood - ADH in kidneys which in turn affects blood pressure
Blood Pressure - spec + stuff on renin-angiotensin system and ACE enzymes/inhibitors for those with high blood pressure. E.g. loss of consciousness could result if bp drops too low
EXTERNAL:
Plant tropisms e.g. phototropism for photosynthesis, maximise productivity
Reflex arc e.g. touching a hot object, importance in damage limitation to tissues as rapid/innate
Chameleons, as an example of ectotherms, which are able to change skin colour for thermoregulation (IR absorbed etc.)
Xerophytes and their natural selection in desert climates as they're adapted to conserve water - discussed Crassulacean Acid Metabolism as another spec + point
Also predator/prey visual/acoustic sensitivity to catch prey/flee from predator for survival
There was definitely scope to discuss a lot of other ideas, so it was a fair essay that encouraged breadth
As for the other questions on the paper, I thought they were more knowledge-based than HSW based when compared to previous years.. Guessing the grade boundaries shouldn't fluctuate too drastically, but it does seem slightly easier than previous years as a general verdict, so I'd say 77ish to get you full UMS compared to 72ish that it's been the past couple of years.
Best of luck, all!