Describe the influence of genes in forming human characteristics.

Discuss the relationship between exercise and susceptibility to infection.

Explain the process of gaseous exchange at the alveoli.

Explain the regulation of adrenaline and insulin levels in the body.

children inherit genes from their parents via sex cells «gametes» ✔

half of inherited genes are from each parent ✔

many millions of different genetic combinations from the same parents are possible ✔

human characteristics «phenotype» are determined by their genes «genotype» ✔

some characteristics are expressed developmentally by genes
OR
genes can be expressed as height / eye colour / hair colour etc ✔

some characteristics require an environmental switch ✔

[5 max]

athletes must have both physical fitness and an effective immune system to withstand infection ✔

high training volume is associated with increased susceptibility to infection ✔

sedentary lifestyle is associated with increased susceptibility to infection ✔

moderate exercise is associated with reduced susceptibility to infection ✔

moderate exercise improves the lymphatic system ✔

moderate exercise decreases glucocorticoid levels «inverse relationship with immunity» ✔

Athletes who overtrain may be more susceptible because of:

lower leucocyte numbers caused by the stress of exercise ✔

inflammation caused by muscle damage ✔

greater exposure to airborne bacteria and viruses because of an increased rate and depth of breathing ✔

Susceptibility to infection, award [2 max] for description of J curve.

Accept annotated diagram of J curve

[5 max]

gases diffuse across the alveoli membrane ✔

movement is from high to low partial pressure/concentration gradient ✔

oxygen partial pressure is higher in air breathed in compared to blood ✔

carbon dioxide has a higher partial pressure in blood compared to lungs ✔

the concentration gradient is maintained due to ventilation / blood flow ✔

diffusion is facilitated by the thin / moist barrier/ large alveoli surface area between blood and alveoli ✔

greater volumes of gases diffusing across alveoli membrane when exercising ✔

Accept answers in the converse where appropriate.

[4 max]

regulated by complex feedback loops ✔

Adrenaline:
can be managed by activity level ✔
can be managed by relaxation techniques (eg meditation) ✔
regulated by «nervous stimulation» of the adrenal gland ✔
stress/anxiety/fear anger can promote adrenaline release ✔

Insulin:
regulated by chemical stimulation of the pancreas ✔
receptors respond to increase in blood glucose / high carbohydrate intake ✔
can be managed by injection / inhalation / infusion ✔
stress can reduce insulin levels ✔

[6 max]

Overall candidates managed to earn at least 2 marks, with many accessing 4 marks.

Most candidates answered this well and accessed 3 marks for the description of the J curve; however, many were unable to explain the reasons why elite athletes were the most susceptible.

Surprisingly this very common exam question was poorly answered. Candidates rarely used key terminology such as diffusion, and concentration of gases. Very few identified where there was a high or low concentration of gases. However, many students were able to identify the factors which made gaseous exchange efficient at the alveoli.

Many candidates were able to access 4 marks for identifying why the hormone would be released and where it was released from; however, few students were able to discuss the regulation.