Answer:
The International Astronomical Union (IAU) downgraded the status of Pluto to that of a dwarf planet because it did not meet the three criteria the IAU uses to define a full-sized planet. Essentially Pluto meets all the criteria except one—it “has not cleared its neighboring region of other objects.”
Barrier effects can assume physical or social forms.Physical barrier effects consist of characteristics of the natural (physical) environment that inhibit the spread of culture. The classic examples are oceans, deserts, mountain ranges, dense forests, and frigid climates.
I would say a natural disaster like a forest fire that could kill trees that are their homes. A forest fire could kill the trees and also the cones they eat for food and thus destroy their habitat and also a source of food and the branches they use to travel from one tree to another in the upper stories of the forest.
Explanation:
The growth in urban areas comes from both the increase in migration to the cities and the fertility of urban populations. ... Therefore, the urbanization of the world is likely to slow population growth. It is also likely to concentrate some environmental effects geographically.
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