Energy transfer in ecosystemsIB MYP Biology: Subtopic test

1. 1
   On the Serengeti plains in East Africa, grass is eaten by zebra, and zebra are hunted by lions. When animals die, bacteria and fungi in the soil break down their remains.

   (a)

   In the food chain grass → zebra → lion, which organism is the primary consumer?

   [1 mark]

   • AThe grass
   • BThe lion
   • CThe zebra
   • DThe bacteria in the soil

   (b)

   Which term describes the bacteria and fungi that break down the remains of dead animals?

   [1 mark]

   • ADecomposers
   • BProducers
   • CPrimary consumers
   • DSecondary consumers

   (c)

   State two ways in which a zebra loses energy so that it is not available to the lion that eats the zebra.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   In an English oak woodland, one large oak tree supports about 2000 caterpillars on its leaves. The caterpillars are eaten by about 20 blue tits, and the blue tits are hunted by a single sparrowhawk.

   (a)

   A pyramid of numbers for this food chain is not pyramid-shaped. What is the main reason?

   [1 mark]

   • AThe caterpillars are larger than the oak tree
   • BEnergy is not lost between the trophic levels
   • CThe sparrowhawk is the producer
   • DThe producer is a single, very large tree

   (b)

   Which diagram would give a pyramid shape for this food chain?

   [1 mark]

   • AA pyramid of numbers drawn to a larger scale
   • BA pyramid of biomass, which compares the dry mass of living material at each level
   • CA food web, which compares the mass at each level
   • DA list of the number of leaves on the oak tree

   (c)

   Explain why the biomass at each trophic level is less than the biomass at the level below it.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A farmer wants to know which of two feeds turns more of its energy into chicken growth. Each chick eats either Feed X or Feed Y for a week. Each chick on Feed X is supplied with 8000 kJ of energy and gains new body tissue containing 1200 kJ. Each chick on Feed Y is supplied with 9000 kJ of energy and gains new body tissue containing 1530 kJ. The farmer used one group of chicks for each feed.

   (a)

   Calculate the efficiency of energy transfer for Feed X and for Feed Y, and state which feed is more efficient.

   [3 marks]

   (b)

   The farmer concludes that Feed Y is better and decides to buy only Feed Y. Evaluate the farmer's conclusion.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A country with a growing population has limited farmland. Its farmers can use a field either to grow wheat for people to eat, or to grow grass and grain to feed cattle for beef. Cattle convert only about 10% of the energy in their feed into new body tissue. The government is considering paying farmers to grow more wheat and rear fewer cattle.

   (a)

   Explain why a field of wheat can feed more people than the same field used to rear cattle for beef.

   [6 marks]

   (b)

   Discuss and evaluate the government's plan to pay farmers to grow more wheat and rear fewer cattle.

   [6 marks]

   Total for question 4: 12 marks

End of questions