Climate is the most fundamental component of the physical environment. Weather: current temp, precipitation, humidity, wind, cloud cover. Climate: long-term description of weather at a given location, based on averages and variation measured over decades. Includes daily and seasonal cycles associated with earth"s rotation and orbit. Geographic distributions of organisms are influenced by extreme conditions, determinants of mortality. Energy gains from solar radiation (1/5 of incoming) must be balanced by energy losses. Latent heat flux: heat loss due to evaporation. Sensible heat flux: energy transfer from warm air immediately above earth"s surface to cooler atmosphere by convection and co nduction. Winds and ocean currents result from differences in solar radiation across earth"s surface. Atmospheric circulation cells are established in regular latitudinal patterns. Surface heating and uplift - differential solar heating of earth"s surface leads to uplift of pockets of air over warmest surfaces. As air expands and cools, water vapor condenses to form clouds.