The sun provides all the energy for evaporation.
Cells will usually divide if they receive the proper signal at a checkpoint in the G1 phase of the cell cycle. In mammalian cells , this checkpoint is called the restriction point. The G1 phase is a phase of the cell cycle that takes place in eukaryotic cell division. In this phase the cell synthesizes mRNA and proteins in preparation for the subsequent steps leading to mitosis. It ends when the cell moves into the S phase of interphase.
Answer:
The Loop of Henle serves to create a concentration gradient throughout the nephron which helps increase the reabsorption of water and certain ions. In the thin descending limb, water is very permeable and is reabsorbed due to the existing concentration gradient in the medulla.
