Earth’s spheres and watery homes

The hydrosphere includes oceans, seas, rivers, lakes, groundwater, glaciers, ice and the water vapour in the air. The biosphere includes every living thing, from the icy poles to hot deserts. A biome is a large region with a similar climate, plants and animals, such as a desert, a forest or a wetland. The two spheres are linked. Plants and animals drink water. Many animals live in water and lay their eggs there. In return living things change water: plants give out water vapour into the air, and animals’ waste enters the water. A good way to study an interaction is to ask: which spheres are in this sentence? A fish swimming in a river belongs to both the biosphere and the hydrosphere. Rain filling a puddle belongs to the hydrosphere alone.