It is because leaves are the main users of photosynthesis in a plant. The sunlight seeps into the leaves, and the leaves transform the sunlight's energy into sugar; their food.
I hope this helps! :)
To be able to compare the results to a sample without any of the independent variable added.
Cell Membrane = Controls what comes into and out of a cell; found in plant and animal cells
The answer is; YES
All organisms share one common ancestor in the beginning of life. Different species have branched at different times from common ancestors hence he evolutionary tree looks like tree called a cladogram. The nodes represent the common ancestry while branches depict divergence. Therefore even fruit flies and the fruit bats even though they do not belong to the same species shared a common ancestor at one time in history.