Relationships between organismsIB MYP Biology: Subtopic test

1. 1
   A farmer in Kenya grows beans. The roots of the bean plants have small swellings called nodules that contain nitrogen-fixing bacteria. The bacteria change nitrogen gas from the air into nitrogen compounds that the plant can use. The plant supplies the bacteria with sugars and a protected place to live.

   (a)

   What type of relationship exists between the bean plants and the nitrogen-fixing bacteria?

   [1 mark]

   • AParasitism
   • BMutualism
   • CPredation
   • DCompetition

   (b)

   Which of these is another example of mutualism?

   [1 mark]

   • AA tapeworm living in the gut of a person
   • BA lion hunting a zebra
   • CTwo bean plants growing close together and competing for light
   • DA fungus (mycorrhiza) growing on tree roots and helping the tree to take in water and mineral ions

   (c)

   Explain how each organism benefits from this relationship.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A man in Buenos Aires becomes ill after eating undercooked beef. A tapeworm is found living in his small intestine. The tapeworm has hooks and suckers on its head and absorbs digested food from the man's gut. The man loses weight even though he is eating normally.

   (a)

   What type of relationship exists between the tapeworm and the man?

   [1 mark]

   • AMutualism
   • BCommensalism
   • CParasitism
   • DPredation

   (b)

   What is the most likely function of the hooks and suckers?

   [1 mark]

   • ATo attach the tapeworm to the wall of the intestine
   • BTo digest the man's food
   • CTo kill the man's cells
   • DTo move the tapeworm out of the gut

   (c)

   Explain why the man loses weight even though he is eating normally.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A school nurse in Muscat compares two treatments for head lice. For each treatment, 50 live lice are placed on a clean sample of hair and the treatment is applied. As a control, 50 lice are placed on a hair sample treated with water only. After 30 minutes the nurse counts the lice that have stopped moving. For shampoo A, 47 lice had stopped moving. For shampoo B, 29 had. With water only, 2 had.

   (a)

   Process the results to find the percentage of lice that stopped moving with each treatment, and state which treatment was most effective.

   [3 marks]

   (b)

   Evaluate the method and suggest two improvements.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   In a region of Uganda, many people, especially young children, suffer from malaria. Local health officials must decide how to reduce its spread. They are choosing between handing out free insecticide-treated bed nets to every household, or spraying insecticide in every village and draining the nearby swamps where the mosquitoes breed.

   (a)

   Describe how malaria passes from an infected person to a healthy person.

   [6 marks]

   (b)

   Discuss which approach the officials should choose. Reach a justified conclusion.

   [6 marks]

   Total for question 4: 12 marks

End of questions