The greenhouse effect is a natural process that warms the Earth's surface. When the Sun's energy reaches the Earth's atmosphere, some of it is reflected back to space and the rest is absorbed and re-radiated by greenhouse gases. ... The absorbed energy warms the atmosphere and the surface of the Earth.
This process would be the one truly responsible for the "evolution" of mitochondria and chloroplasts as we know them from their prokaryotic ancestors. The cell process that would have initiated endosymbiosis is endocytosis; the process of taking things inside the cell
