As Earth rotates, different parts of Earth receive sunlight or darkness, giving us day and night. Since different parts of Earth enter and exit daylight at different times, we need different time zones. In the late 1800s, a group of scientists figured out a way to divide the world into different time zones.
homologous chromosomes ... sister chromatids
The majority of electricity is generated at a power station by electromechanical generators, primarily driven by heat engines fueled by combustion or nuclear fission but also by other means such as the kinetic energy of flowing water and wind.
By the late 1830s, botanist Matthias Schleiden and zoologist Theodor Schwann were studying tissues and proposed the unified cell theory. The unified cell theory states that: all living things are composed of one or more cells; the cell is the basic unit of life; and new cells arise from existing cells.
