It allows the scientist to determine the effect of the changed variable , it also allows samples and organisms to be tested under comfortable conditions
For the first half of your question, plants do need to eat. In fact, they are autotrophs, which means they are self feeders.
Answer:
The <u><em>second </em></u>line of defense.
Explanation:
In our bodies the <em><u>second line of defense</u></em> includes active immunity. It contains non-specific immune responses, but yet still contains specific responses for certain things such as inflammatory and fevers.
Precipitation needs to happen to keep the water cycle balanced
