Programme For International Student Assessment Pisa / Sample Science Passage 7: Biodiversity


Read the following newspaper article and answer the questions which follow. 

BIODIVERSITY IS THE KEY TO MANAGING ENVIRONMENT 
An ecosystem that retains a high biodiversity (that is, a wide variety of living things) is much more likely to adapt to human-caused environment change than is one that has little. 

Generally, loss of biodiversity should be regarded seriously, not only because the organismsthat have become extinct represent a big loss for both ethical and utilitarian (useful benefit) reasons, but also because the organisms that remain have become more vulnerable (exposed) toextinction in the future. 

Consider the two food webs shown in the diagram. The arrows point from the  organism that gets eaten to the one that eats it. These food webs are highly simplified comparedwith food webs in real ecosystems, but they still illustrate a key difference between more diverseand less diverse ecosystems. 





Food webs A and B are in different locations. Imagine if Leaf Hoppers died out in both locations. Which one of these is the best prediction and explanation for the effect this would have on the food webs?

The effect would be greater in food web B because the Parasitic Wasp has several food sources in web B.
The effect would be greater in food web A because the Parasitic Wasp has only one food source in web A.
The effect would be greater in food web B because the Parasitic Wasp has only one food source in web B.
The effect would be greater in food web A because the Parasitic Wasp has several food sources in web A.

In lines 9 and 10 it is stated that 'Food web A represents a more diverse ecosystem with, as a result, many more alternative feeding pathways.' Look at FOOD WEB A. Only two animals in this food web have three direct (immediate) food sources. Which two animals are they?

Native Cat and Butcher Bird
Parasitic Wasp and Leaf Hopper
Parasitic Wasp and Spider
Native Cat and Parasitic Wasp