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Date	May 2018	Marks available	1	Reference code	18M.2.SL.TZ2.1
Level	Standard level	Paper	Paper 2	Time zone	Time zone 2
Command term	Calculate	Question number	1	Adapted from	N/A

Question

Edible insects have been a part of traditional human diets in many countries. For example, crickets are insects commonly eaten in Asia and Africa. Many studies have looked at the prospects of raising insects on a commercial scale for direct human consumption as food or indirectly by feeding insects to farm animals.

One factor to consider is which organisms are most efficient at converting the feed they eat into animal protein that can be consumed. A study compared the percentage of mass that was edible in two common farm animals and in crickets.

The yellow mealworm (Tenebrio molitor) is native to temperate regions of the world and has been studied as a possible means of producing food in countries with that type of climate. The amino acid content of yellow mealworms and cattle was analysed. The table shows the results for seven amino acids that are required in the human diet.

The environmental impact of producing protein from mealworms was compared with the impact of producing traditional protein sources. The graphs show the greenhouse gas production (global warming potential) and land use due to the production of 1 kg of protein from mealworms, chickens and cattle.

Identify which organism has the highest percentage of edible mass.

[1]

a.i.

Calculate how much more feed is required by cattle than chickens to produce 1 kg of live mass.

[1]

a.ii.

Identify which organism requires the least feed to produce 1 kg of edible mass.

[1]

a.iii.

Distinguish between the amino acid contents of yellow mealworms and cattle.

[1]

b.i.

Predict, with a reason, whether the amino acid composition of yellow mealworms or cattle is more suitable for a human diet.

[1]

b.ii.

Outline the differences between the environmental impact of using mealworms and traditional farm livestock for protein production.

[2]

Birds and mammals maintain constant body temperature despite considerable losses of body heat to the environment. In insects such as mealworms, body temperature is variable and is often the same as the temperature of the environment or only slightly above it. Analyse the data in the bar charts, using this information.

[2]

Using all the relevant data in this question, discuss the use of insects as a major food source for humans.

[3]

Markscheme

cricket

a.i.

25 − 4 = 21kg «more required for cattle»

Must state unit kg.

a.ii.

cricket

a.iii.

a. mealworms have more isoleucine/leucine/valine than cattle

b. cattle have more lysine/methionine/phenylalanine/threonine

c. the total proportion of these amino acids is «slightly» greater in cattle (188 to 176)

b.i.

a. cattle as they are more closely related to humans

b. cattle as they are more likely to have proteins with a similar amino acid composition to humans OWTTE.

c. cattle as they contain a «slightly» higher proportion of «essential» amino acids required in human diet (188 to 176)

OWTTE

b.ii.

a. mealworms contribute much less to global warming than other traditional farm livestock for protein production

b. mealworms require less land use than other traditional farm livestock for protein production

Accept converse or OWTTE.

a. cell respiration required to generate heat (lost to environment) to maintain body temperature

b. birds/chickens and mammals/cattle carry out cell respiration at higher rate than insects

c. «chickens/cattle therefore» generate more CO₂ per kg protein produced

d. «chickens/cattle» need more food/land area to produce body mass

e. feed conversion ratios are lower in mealworms/insects/cold blooded animals as they do not need to maintain a constant body temperature (accept converse)

a. insects/crickets have the highest edible percentage

b. insects have the lowest feed conversion ratio/produce the most edible mass per kg of food they eat

c. insects supply amino acids required in the human diet

d. insects cause less global warming/use less land area per kg of protein produced

e. in western countries, there is a disgust factor/cultural factors about eating insects which would need to be overcome before they could be used as a significant food source

f. insects may supply less proportions/content of amino acids required in human diets