Predator-prey relationshipsIB MYP Biology: Subtopic test

1. 1
   In a nature reserve in Canada, the populations of snowshoe hares (prey) and lynx (predators) were counted every year for 20 years. The hare population peaked at about 140 000 in year 4 and again in year 14. The lynx population peaked at about 60 000 in year 6 and again in year 16.

   (a)

   How many years are there between successive peaks in the hare population?

   [1 mark]

   • A4 years
   • B6 years
   • C2 years
   • D10 years

   (b)

   Each lynx peak comes two years after a hare peak. What is this delay called?

   [1 mark]

   • AA time lag
   • BA migration
   • CAn extinction
   • DAn adaptation

   (c)

   Explain why each lynx peak comes after the hare peak.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A cheetah hunts gazelles on an African grassland. The cheetah has a streamlined body, powerful leg muscles and eyes at the front of its head. The gazelle has eyes at the sides of its head, long legs for fast running and a brown coat.

   (a)

   How do the eyes at the front of the cheetah's head help it to catch prey?

   [1 mark]

   • AThey give it a wide field of view
   • BThey help it to judge distances accurately
   • CThey allow it to see in the dark
   • DThey help to keep dust out of its eyes

   (b)

   Why are the gazelle's eyes at the sides of its head?

   [1 mark]

   • ATo judge the distance to the cheetah
   • BTo help it to see in bright light
   • CTo see predators approaching from nearly all directions
   • DTo make it easier for it to run fast

   (c)

   Explain how the gazelle's brown coat helps it to survive.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A class investigates camouflage using paper 'insects' on a green lawn. In each trial the teacher scatters 20 green, 20 yellow and 20 red paper insects, all the same size, over the same area of the lawn. Ten students act as predators and each has 20 seconds to collect as many insects as they can. The trial is repeated three times with fresh insects. In total, the students collected 9 green, 24 yellow and 41 red insects.

   (a)

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

   [3 marks]

   (b)

   Calculate the percentage of red insects collected, explain what the results suggest about camouflage, and evaluate one limitation of the model with an improvement.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   On a remote island, rabbits that were introduced many years ago eat the crops of local farmers. A small population of foxes also lives on the island and hunts the rabbits. A 30-year survey showed that the numbers of both animals rise and fall in regular cycles, with each peak in the number of foxes always coming after a peak in the number of rabbits. The farmers now ask the government either to release more foxes or to put out poisoned bait to reduce the number of rabbits.

   (a)

   Explain why the numbers of rabbits and foxes rise and fall in cycles.

   [6 marks]

   (b)

   Discuss whether the government should release more foxes or use poisoned bait. Reach a justified conclusion.

   [6 marks]

   Total for question 4: 12 marks

End of questions