Which of the following can upset the balance of an ecosystem?
too much water
not enough water
too much light
not enough light
all of the above
none of the above

Correct E). All of the above

An ecosystem is said to be balanced  when all the all the plants, animals and the non-living components of the environment are in harmony. It may get disturbed or loos its harmony when there is a increased pollution, an increase in the number of the human population etc.

Ecological balance occurs when nature or man caused the disturbance to the natural balance of the ecosystem. Ecological balance is very important in order to ensure that no particular organism or species is overused or exploited.

straight fertilizers

a "theory" a suggestion that is not 100 % accurate, or a figure. some people say its a theory because they of all the passed theory's about one subject. it depends sometimes theory might be accurate and sometimes they are.