Energy flow, pyramids and cyclesIB MYP Sciences: Mind map

Exam questions on Energy flow, pyramids and cycles

1. In a lake in Uganda, the algae capture 5000 kJ of energy per square metre each year. Tiny animals called zooplankton eat the algae, and small fish eat the zooplankton.
   Assume that 10 % of the energy is passed on at each trophic level. Calculate the energy available to the small fish per square metre each year.2 marks
2. A tree in a tropical forest in Costa Rica takes in carbon for decades as it grows. Eventually it dies and falls to the forest floor. Elsewhere in the world, the remains of ancient forests were buried millions of years ago and slowly turned into coal. Some of that coal is now burned in a power station.
   Describe how the carbon in the dead tree on the forest floor returns to the atmosphere.2 marks
3. An ecology class in Otago, New Zealand, studies a pasture. They collect all the organisms from several areas of 1 m², dry them and find the mean dry mass (biomass) per square metre. They find 1200 g of grass, 90 g of grasshoppers and 8 g of frogs. The grasshoppers eat the grass and the frogs eat the grasshoppers. The class wants to use the results to show how biomass changes along the food chain.
   Calculate the percentage of the biomass of the grass that is found in the grasshoppers, and the percentage of the biomass of the grasshoppers that is found in the frogs. Comment on your answers.3 marks