Unicellular organisms excrete waste by a contractile vacuole. A vacuole is membrane-enveloped organelle in a cell that is found in lots of microorganism. It expands, filling with water then contracts, removing all of its contents to the exterior of the cell.
They can protest to use safer sources of energy like power plants.
Pure water has a pH level of 7, which means it is neutral on the pH scale. If you want to increase the pH of water, you must add an alkaline substance to it. The pH scale ranges from 0 to 14, with anything above 7 being alkaline, and anything below 7 being acidic.
The water molecules move by osmosis into the cell from high water concentration to low water concentration.
Answer:
The return of blood to the heart is assisted by the action of the skeletal- muscle pump. As muscles move, they squeeze the veins running through them. Veins contain a series of one-way valves, and they are squeezed, blood is pushed through the valves, which then close to prevent backflow.
