1.2 The Water Cycle See pages 24-25.

The Water Cycle Water is required by all living things to sustain life. Water is able to cycle through the biosphere through abiotic and biotic factors in the environment. The cycling of water through the environment depends on energy from the Sun.

The Water Cycle The water cycle has no starting point. It carries on like a big circle that involves water moving from the clouds to the Earth, and back up to the sky. Water can enter back up into the atmosphere through a number of pathways.

The Water Cycle Water falls to the Earth in the form of precipitation (as rain, snow, hail or sleet). It can fall into waterways (such as oceans, rivers, lakes), or it can fall directly onto the ground.

The Water Cycle Water that falls onto the ground may do one of a number of things: It can run along the surface of the ground into water ways (this water is called run-off). It seeps through the soil . It may eventually reach underground lakes called aquifers. Water that seeps through the soil may also flow into water bodies (such as lakes, ponds, wetlands, oceans). It may be taken in by animals and plants.

The Water Cycle Liquid water from open water bodies (e.g. lakes, ponds, oceans) evaporates. (When water receives heat from the Sun, the heated water changes state from liquid to gas.) The water vapour (gas) travels up into the atmosphere where it condenses to form clouds.

The Water Cycle Plants on the Earth’s surface release water vapour from their leaves (a by-product of reactions in their cells). This process of releasing water from the leaves of plants is called transpiration. The water vapour released from plants travels upward into the atmosphere and condenses to form clouds as well.

The Water Cycle The condensed water vapour in clouds forms droplets that become heavier and heavier, until they drop as precipitation. This cycle continues.

The Water Cycle

The Water Cycle The water cycle video (p. 25 – 10 min video): http://www.sciencesource2.ca/pgs/book9_unitA.php

The Water Cycle Test yourself: http://education.jlab.org/reading/water_cycle.html