 Today we're talking about earth system science and biology plays a huge role in earth systems especially plant biology and photosynthesis. The sunlight comes in and some of that energy is captured in carbon dioxide and some of that energy it strikes a green leaf and also water leaves the leaf and there's a lot of energy transfer to evaporating water so the photosynthesis cools the planet a huge amount and stores sunlight as chemical energy in the form of carbohydrates in the the food that we eat and in the material that makes up plants. Now that's called net primary productivity when the solar energy is captured in the form of plant biomass and that supplies the whole food system the whole ecosystem from the microbes in the soil to animals that chew on leaves it all starts with photosynthesis. Photosynthesis is taking the the water cycle so sunlight's driving the water cycle which is fixing the energy and the photosynthesis itself is measured as gross primary productivity and almost half of the energy that the plants capture in photosynthesis is used by the plants to maintain and to grow new biomass and then at the end of the season the leaves drop and some of the small branches or crops are harvested and decomposition happens so that's that's energy by the microbes that are decomposing the plant biomass that's heterotrophic respiration and much of the carbon in the carbon cycle is released to the atmosphere so there's a little bit left over a few percent left over and and what's left is called net ecosystem productivity and that accumulates each year and that's drawing down some of our pollution in the atmosphere and restoring a balance unless disturbance pests or fires also release that that biomass that productivity and what's left at the end is the net biome productivity so that's the way the earth system regulates energy from the sun through the water cycle and the carbon cycle and it's very important in this living planet