Meiosis: cell division into four daughter cells (each has half the number of chromosome of the parent cell)
mitosis: cell division that results in two daughter cells (each has the same number and type of chromosomes as the parent cell)
By time......................
To inform others of their work
Agricultural society, if I understand the question correctly.
Phospholipids have 2 faces or poles: one hydrophobic (the tails which "run away" from water) and one hydrophilic (the heads which "like" water).
This means that when in a double layer in a aqueous environment, the heads will face the water and the tails will face each other.