A-LevelBiologyHomeostasis9700/43 · May/June 2021 · Q611 Marks

(a) The bottlenose dolphin, Tursiops truncatus, is an aquatic mammal. It has adaptations to conserve heat when swimming in cold water. Fig. 6.1 shows a bottlenose dolphin. [Figure 6.1]

(a)(i)The arteries in the bottlenose dolphin that carry blood to the flippers are surrounded by veins bringing blood back to the rest of the body. Outline how this arrangement of blood vessels is an adaptation to conserve body heat.[1]
(a)(ii)When a dolphin has exercised for a long time, it may need to lose excess heat. Unlike humans, dolphins do not produce sweat. Suggest how a dolphin may lose excess heat.[1]
(b)(i)The control of blood glucose concentration in dolphins is the same as in most mammals. A study was carried out to investigate the concentration of insulin in the blood of dolphins that were provided with a diet of fish, supplemented with glucose. • One group of dolphins ate fish with 3g of glucose for every kg of fish. • Another group ate fish with 11 g of glucose for every kg of fish. The concentration of insulin in the blood was measured 60 minutes before being fed, at the time of being fed and at regular intervals afterwards. Measurements were also taken for a third group of dolphins, at the same time intervals, that were not fed any fish (fasting). The results of the study are shown in Fig. 6.2. [Figure 6.2] Describe the trends shown in Fig. 6.2.[4]
(b)(ii)The mean concentration of insulin in the blood changes over time for the dolphins that were fed fish with 11 g of glucose per kg of fish. Calculate the rate of change in the mean concentration of insulin in this group of dolphins from the time of being fed until the concentration reaches its maximum. Show your working.[2]
(c)Blood glucose concentration is regulated by negative feedback. Explain what is meant by negative feedback.[3]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (May/June 2021). The mark or mark type is shown in brackets.

[1] (a)(i) idea of heat transfer from artery to veins;
[1] (a)(ii) vasodilation / description; R capillaries / blood vessels move to skin surface
[1] (a)(ii) behavioural response; e.g. dive down to cooler waters before surfacing for air
[1] (b)(i) concentration of insulin (relatively) constant for all groups before being fed ;
[1] (b)(i) (fasting dolphins) insulin concentration very little change ;
[1] (b)(i) (fed dolphins) insulin concentration increases then decreases ;
[1] (b)(i) (fed dolphins) for 11 g/kg dolphins steep, increase / decrease, in insulin concentration;
[1] (b)(i) (fed dolphins) for 11 g/kg dolphins high(est) peak in insulin concentration ;
[1] (b)(i) data quote for mp3 or mp4 with time in min; 3 kg 21 at 0 min 30 at 180 min 20 at 240 min 11 kg 10 at 0 min 79 at 90 min 18 at 480 min
[1] (b)(ii) 79-10 / 90 ;
[1] (b)(ii) = 0.77 ;
[1] (c) change in a parameter;
[1] (c) detected by receptor;
[1] (c) coordination / described;
[1] (c) (corrective) action taken by effector ;
[1] (c) return to, set point / norm / optimum ;