The biosphere
The biosphere is the shell of Earth where living things exist. It includes the lower part of the atmosphere, the upper part of the lithosphere (soil) and the whole hydrosphere. Its main difference from the other shells is the presence of living organisms; people live in the biosphere too. Life is unevenly spread: most organisms live on the land surface, in the soil, in the air near the ground and in the sunlit surface waters of the ocean; the most species are in the wet forests near the equator. Natural zones are large natural complexes that differ in climate, soil, plants and animals; they change from the equator towards the poles: wet equatorial forests (about +25 °C all year and over 2000 mm of rain a year), savannas, deserts (100–200 mm of rain a year), steppe, mixed and broad-leaved forests, taiga, tundra and Arctic deserts. In mountains the zones also change from foot to summit – this is altitude zonation.
Poster: on a large sheet draw coloured bands of natural zones from the equator towards a pole and for each write one typical plant, one animal, and the temperature and rainfall. Present it in your group. Safety: use scissors and glue carefully; keep paint out of mouths.