Habitats and ecosystemsIB MYP Biology: Subtopic test

1. 1
   In the dunes of the Sahara Desert, a group of about forty fennec foxes lives alongside desert plants, beetles, lizards and other animals. Daytime temperatures reach over 40 °C, the sand is dry, and rain is rare. Fennec foxes have very large ears and pale fur, and they hunt mainly at night.

   (a)

   All the fennec foxes living in the dunes are counted by a zoologist. Which term describes this group of foxes?

   [1 mark]

   • AA community
   • BA population
   • CA habitat
   • DAn ecosystem

   (b)

   Which of the following is an abiotic factor in the fennec fox's habitat?

   [1 mark]

   • AThe number of beetles available as food
   • BThe presence of desert plants
   • CA predator such as an eagle owl
   • DThe daytime temperature of the sand

   (c)

   Explain how the fennec fox's large ears help it to survive in the desert.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Scientists studying the Antarctic coast describe a range of organisms: an icefish whose blood contains a natural antifreeze, an emperor penguin that huddles with others through the winter, and a lichen that grows on bare rock.

   (a)

   Which feature is shared by the icefish, the emperor penguin and the lichen, as it is by all living things?

   [1 mark]

   • AThey all have a backbone
   • BThey all make their own food by photosynthesis
   • CTheir bodies are made of cells that contain DNA
   • DThey all have a skeleton made of bone

   (b)

   Which type of adaptation is the emperor penguin's huddling together through the winter?

   [1 mark]

   • ABehavioural
   • BStructural
   • CPhysiological
   • DGenetic

   (c)

   The icefish has natural antifreeze in its blood. State the type of adaptation this is and explain how it helps the icefish to survive.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student investigates whether woodlice prefer damp or dry conditions. She uses a choice chamber with a damp side and a dry side, separated by a mesh floor. She places ten woodlice in the centre, covers the chamber with a lid and counts how many are on the damp side after ten minutes. She repeats this four times with the same ten woodlice, and finds 8, 7, 9 and 8 woodlice on the damp side.

   (a)

   Identify the independent variable, the dependent variable and one control variable in this investigation.

   [3 marks]

   (b)

   Process the results and evaluate the student's method. State whether the results support the hypothesis that woodlice prefer damp conditions.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Along the Pacific coast of North America, kelp forests are home to sea otters, sea urchins, fish and many other species. Sea urchins eat kelp. Sea otters eat sea urchins. Young fish shelter among the kelp fronds. In the 1800s sea otters were hunted almost to extinction in some areas, and the kelp forests there then largely disappeared.

   (a)

   Explain what happened to the kelp forests when sea otters were removed, and why the loss of the otters affected other organisms in the ecosystem.

   [6 marks]

   (b)

   A coastal town wants to bring sea otters back to a bay where the kelp has disappeared. Local fishers are worried, because sea otters also eat the shellfish that they sell. Discuss and evaluate the proposal to reintroduce sea otters.

   [6 marks]

   Total for question 4: 12 marks

End of questions