Chapter 4 Practice Paper: Organisms and their Environment — question paper

Section A: Multiple-choice questions[10 marks]

Choose the one correct answer for each question.

1. 1

   Energy flows through an ecosystem but matter cycles. The key difference is that energy

   1. Ais destroyed at each trophic level
   2. Bis stored forever in the top carnivore
   3. Ccycles through decomposers like carbon does
   4. Dleaves the ecosystem as heat that cannot be re-captured, so it must be replaced by sunlight
   ( )
2. 2

   A food chain stores 8 000 kJ in producers and 800 kJ in primary consumers. The transfer efficiency is

   1. A0.1%
   2. B1%
   3. C10%
   4. D80%
   ( )
3. 3

   A pyramid of numbers is inverted when

   1. Aproducers are larger than all consumers combined
   2. Ba single large producer, such as a tree, supports many small consumers
   3. Cdecomposers are counted in the producer bar
   4. Dthe ecosystem contains no herbivores
   ( )
4. 4

   Insecticide concentrations along a food chain were 0.05 ppm in water and 5 ppm in the top carnivore. The overall increase is

   1. A10 times
   2. B50 times
   3. C100 times
   4. D2500 times
   ( )
5. 5

   Which action both reduces CO₂ emissions and restores a carbon sink?

   1. Aswitching to renewable energy only
   2. Bbuilding more roads
   3. Cdraining a mangrove swamp for development
   4. Dreforesting cleared land
   ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided.

1. 1

   In a grassland food chain, the producers contain 50 000 kJ of energy, the primary consumers 5 000 kJ, and the secondary consumers 500 kJ.

   1. (a)

      Name the trophic levels of the primary and secondary consumers.

      [1]
   2. (b)

      Calculate the efficiency of energy transfer from producers to primary consumers.

      efficiency =%[2]
   3. (c)

      State three ways in which the remaining energy is lost, and explain why food chains rarely extend beyond five levels.

      [3]
2. 2

   The described diagram shows the carbon cycle: arrows between the atmosphere, a forest, animals, a factory burning fuel, and leaf litter on the soil.

   1. (a)

      Name the process that moves carbon dioxide FROM the atmosphere into the forest, and the cell structure that carries it out.

      [2]
   2. (b)

      List the processes that release carbon dioxide into the air, choosing one from living organisms and one from the factory shown.

      [3]
   3. (c)

      Explain why cutting down the forest, rather than the factory alone, threatens to unbalance the carbon cycle.

      [2]
3. 3

   A lake receives runoff from a farm sprayed with a persistent insecticide. Water samples and tissue samples give these concentrations: water 0.01 ppm; plankton 0.1 ppm; small fish 1 ppm; fish-eating birds 10 ppm.

   1. (a)

      Show that the insecticide concentration multiplies tenfold at each step, and calculate the overall increase from water to birds.

      [3]
   2. (b)

      Explain why the concentration increases up the food chain even though the water itself tests nearly clean.

      [2]
   3. (c)

      State one effect on the birds and one farm practice that would reduce the risk.

      [2]