A living organism, such as a pigeon lives in a certain area because it can find all it needs to survive there. In and around the school's courtyard, pigeons can find enough food and enough water. In addition, they can tolerate the cold temperatures in winter and the presence of several hundred humans. The same is true for the trees and the other birds who live in the courtyard.

Other organisms, such as lizards, could never survive in the courtyard. There is not enough food for a lizard (not enough insects) and the temperature in the winter is much too cold for it to survive.
 

Likewise, there is not enough water for an organism such as a frog.

Animals are not the only organisms which tend to live in certain areas because of the temperature and humidity. The environment in the courtyard might not be right for palm trees, for example, but it suits sycamores such as the half dozen London plane trees which are planted in it. Like many of the trees planted in Paris, London plane trees are particularly resistant to urban air pollution.

Another reason palm trees planted in Paris often die is because they cannot survive the freezing weather in the winter.

Discover the extremes of the lithosphere and the hydrosphere

Humans have an influence on the organisms which populate the courtyard. First of all, there is no soil in the courtyard because any particles that might collect there are removed by the maintenance staff regularly. As a result, no seedlings or shoots of grass can be observed growing because they have nothing to grow in. The only soil that might exist is below the asphalt and any seeds which might be under there would never be able to pierce through with their seedlings.

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