In an experiment, the independent variable is the one that you:
1. change or manipulate
2. hold constant throughout the entire experiment
3. measure in response to a changing variable
and
the dependent variable in an experiment is:
1. one you hold constant. the experiment depends on never changing the dependent variable.
2. one you change or manipulate. everything depends on what you do to this variable.
3. the one you measure. the dependent variable depends on how you change the independent variable.

Independent variable is that which we change or manipulate.

Explanation:

By changing the independent variable, there is a corresponding change in the dependant variable which we intend to measure.        

The dependant variable is the one you measure. The dependant variable depends on how you change the independent variable.

Explanation: For example we want to observe speed of a car change with respect to time.

Here, time is the independent variable as it has its own pace regardless of the car. However, at different instances of time , the car has different speeds. Thus, the speed of the car is the dependant variable as it depends on time.

from my research i have to the conclusion that decomposers, such as fungi, bacteria and invertebrates, play a critical role in nutrient cycling and without them the earth's ecosystem may not support life as we know it. elements such as carbon, nitrogen and phosphorus exist in limited amounts on earth, although huge amounts of carbon are being released into the atmosphere from underground sources now by humans. it is still extremely important that other nutrients be retained by the process of re-use. decomposers are organisms that are able to chemically break down dead material and make these elements available for use by other organisms. without this breakdown of dead material, dead bodies would pile up. so decomposers also play a role in clean up also. without them, life might not continue as we know it and dead material would overwhelm the earth.    

so whats the answer