Feed conversion ratio (FCR) is the mass of animal feed in kilograms required for farmed animals to produce one kilogram of edible mass. For example, the FCR for salmon is 1.2 and for chicken is 2.2. Deduce the implication of these ratios for sustainability.

Models are used as representations of the real world. Evaluate the use of food webs to represent ecological communities.

Explain why some biologists think protecting keystone species would help preserve biological diversity in an ecosystem.

Outline what is meant by the niche concept.

a. higher FCR implies less sustainability ✔ Do not accept efficiency instead of sustainability.

b. salmon based diet is more sustainable/chicken is less ✔

c. salmon diet would have lower energy losses/chicken diet higher energy losses ✔

d. salmon diet will produce less waste/chicken more✔

Advantages:
a. food webs summarize all possible food chains «in the community» ✔ OWTTE

b. realistic representation ✔

Limitations:
c. some communities/ecosystems are too complex to represent ✔

d. only shows qualitative information/not quantitative data
OR
saprotrophs/abiotic factors not taken into account ✔

Needs one advantage and one limitation to obtain [2].
Do not accept mentions of trophic levels.

a. «research demonstrates that keystone species» have a «disproportionately» large effect on their environment relative to abundance
OR
«keystone species» maintain a balance in the «stable» numbers of each species within a community
OR
«keystone species» have a large impact in preserving and stabilizing the biodiversity by preventing overpopulation/monopoly/out competition ✔

b. a keystone species’ disappearance would start a domino effect/other species in the habitat would also disappear
OR
their loss leads to an imbalance in the food web
OR
their loss leads to a decrease in biodiversity ✔

Do not accept protecting keystone species prevents disappearance of other species since it repeats the question.

a. the role of an organism in its environment
OR
functional position of an organism in its environment ✔

b. includes «spatial» habitat AND feeding activities AND interactions with other species in the community ✔ All required.

c. no two species can occupy the same niche ✔

d. a niche can be fundamental or realized ✔ OWTTE