The nucleus tells the cell what to do, and also contains chromosomes, which has the cell's genetic material.
I mean each Animal has a purpose in order to keep the food chain in line, for example sharks if they went extinct there would be more seals and more fish and less of this and that. Each animal plays a certain part on earth in order to keep everything normal.
Answer:
Independent variable - time. Dependent variable - the distance moved by the bubble along the capillary tube. Control variables - temperature, air flow or draughts, adequate supply of water.
