Biology 9700 · AS & A Level · Testing for biological molecules
Testing for biological molecules — practice question
Study the passage below.
Catfish are an economically significant freshwater fish species that are used as food by humans. In the wild, catfish occur in a wide range of large freshwater environments, including rivers, lakes and reservoirs. In North America, they are commonly kept in catfish ponds, which are man-made environments. Each pond acts as a self-supporting ecosystem with its own collection of organisms. Catfish eat live and dead fish, amphibians, insects and even dead mammals that are found on the pond bottom. Several species of phytoplankton are always present in these ponds. These are tiny organisms suspended in the water, and they are vital for the growth of all the other pond organisms.
(a(i))[4]
Using the passage, state what is meant by the terms habitat and community.
(a(ii))[1]
Name the producer in the pond ecosystem.
(a(iii))[3]
Describe the characteristics of producers.
(b(i))[3]
Studies of the energy efficiency of rearing catfish in ponds have shown that only 15-20% of the energy absorbed by the catfish population in their food is used to increase their total biomass.
Explain why only some of the energy absorbed by the catfish is used to increase biomass.
(b(ii))[1]
In the wild, only about 10% of the energy absorbed by the catfish in their food is used to increase biomass.
Suggest why this percentage is lower in the wild than in the pond.
Worked solution & mark scheme
This 12-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Correct meaning of habitat and community” …