Relationships between organismsIB MYP Biology: Mind map

Exam questions on Relationships between organisms

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.
   Explain how each organism benefits from this relationship.2 marks
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.
   Explain why the man loses weight even though he is eating normally.2 marks
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.
   Process the results to find the percentage of lice that stopped moving with each treatment, and state which treatment was most effective.3 marks