Periodic table below, which elements are predominantly gases with low densities

as resources become scarce because of population growth, the growth decreases after few years due to lack of resources and food.

stimulus is a change in the environment that causes an organism to react. the response is the reaction to the stimulus. some examples of stimuli for zebras are drought, to many predators, and bad feeding grounds such as dead grass or plants. zebras respond to stimuli just like all other living organisms