CO2 is an important trace gas in Earth's atmosphere. It is an integral part of the carbon cycle, a biogeochemical cycle in which carbon is exchanged between the Earth's oceans, soil, rocks and the biosphere. Plants and other photoautotrophs use solar energy to produce carbohydrate from atmospheric carbon dioxide and water by photosynthesis. Almost all other organisms depend on carbohydrate derived from photosynthesis as their primary source of energy and carbon compounds.
Topographic maps use contour lines to show elevation.
Topographic maps, often called "topo maps," feature contour lines to portray the shape and elevation of the land.
Contour lines (lines of equal elevation) that are close together indicate steep terrain, while lines that are far apart indicate flat terrain.
Such maps also usually portray both natural and artificial features. They show and name natural land formations such as mountains, valleys, plains, lakes, rivers and vegetation. They also identify particular man made features such as roads, boundaries, transmission lines and major buildings.
