Air & Water Lesson 2. Chapter 6 Conserving Our Resources

Transcription

1 Air & Water Lesson 2 Chapter 6 Conserving Our Resources

2 Objectives Summarize the importance of air. Describe the water cycle.

3 Main Idea Living things use air and water to carry out their life processes.

4 Vocabulary atmosphere the layer of gases that surround Earth ozone layer a layer of ozone gas in Earth s atmosphere that screens out much of the Sun s ultraviolet rays water cycle the continuous movement of water between Earth s surface and the air

5 precipitation water that falls from clouds to the ground in the form of rain, sleet, hail, or snow watershed the region that contributes water to a river or a river system water table the upper surface of the groundwater that lies between topsoil and tightly packed rocks

6 precipitation watershed water table aquifer reservoir

7 How is air useful? Air makes life possible. Air is part of the atmosphere which consists of nitrogen and oxygen, also water vapor, argon gas, and other gases. It protects us from meteors and radiation. It is also a source of energy.

8 Oxygen Carbon Dioxide Cycle Oxygen is necessary for respiration, the breaking down of food to produce energy. Carbon dioxide is a waste product of respiration. Plants need carbon dioxide to use in photosynthesis. Oxygen is a byproduct.

9 Earth s Atmosphere Plants need nitrogen to make proteins. Nitrogen is converted into a chemical form by bacteria which is usable by plants. Consumers eat the plants and produce waste or die, releasing it back into the atmosphere or soil.

10 Clouds in the atmosphere block sunlight during the day and trap heat during the night which protects life from extreme temperatures. Earth s atmosphere contains the ozone layer. It prevents 99% of the sun s ultraviolet rays.

11 Wind is a source of energy. Wind moves the blades of a windmill driving a wind turbine, a machine that generates electricity. Wind is also used in recreation.

12 Quick Check Summarize Describe how Earth s atmosphere sustains life. The atmosphere contains oxygen and carbon dioxide for respiration and photosynthesis. It regulates air temperature and blocks UV rays.

13 Critical Thinking What might happen to the atmosphere if the number of plants on Earth declined significantly? Carbon dioxide would build up in the atmosphere and the atmosphere would contain less oxygen.

14 Where do we find water? Water is one of Earth s most important resources but only a small fraction of Earth s water is usable. Fresh water is constantly renewed by the water cycle.

15 Water Cycle Water evaporates from bodies of water on land. The water vapor rises, as it cools it condenses into clouds of tiny droplets. When the droplets are heavy enough, they fall to the land as precipitation. Groundwater seeps into the land (infiltration), runoff moves downhill and enters streams and rivers.

16 Watersheds Watersheds are generally bordered by landforms similar to mountain ridges.

17 Quick Check Summarize Identify the steps in the water cycle. evaporation, condensation, precipitation, runoff

18 Critical Thinking Why is the water cycle so important to living things? The water cycle provides organisms with fresh water that is needed to carry out life processes. It is also the habitat for water dwelling organisms.

19 How is water useful? More than 97% of the Earth s water is salt water. The salt in the oceans, halite or rock salt, and other materials are left behind when the water evaporates. The ocean levels will remain about the same even though water evaporates because new water is being added by precipitation and rivers.

20 Ocean water contains almost every element and mineral. Producers use carbon dioxide and sunlight to make food. Consumers eat the producers containing those elements and minerals.

21 Desalination is the process of turning salt water into fresh water by boiling and evaporating the salt water. The evaporated water is collected and condensed as fresh water.

22 Global currents circulate warm water from the equator and cold water from the polar regions. These currents help form weather patterns on land.

23 Using Fresh Water Rain, snow, and groundwater seeps into the ground and fills in among the rocks and soil. The top of this water filled space is the water table. The depth varies.

24 A spring is where groundwater comes out of the ground; this is where the water table meets the surface.

25 Wells are holes that are dug below the water table.

26 Some wells go into an aquifer and need a pump. A confined aquifer is squeezed between tightly packed layers of rock. An artesian well extends down into a confined aquifer and does not need a pump.

27 Quick Check Summarize Describe some of the places where people find fresh water. People find fresh water where the water table reaches the surface (such as ponds, lakes, rivers, and streams), in wells (ordinary and artesian), and in reservoirs.

28 Critical Thinking Why is it important to conserve fresh water? Conserving fresh water is important because fresh water represents only about 3 percent of the water on Earth.

29 What are droughts and floods? A drought is a lack of precipitation over an extended period of time. The dust bowl occurred in the southern Great Plains during the 1930 s when the topsoil blew away and the crops failed. To help minimize erosion farmers used contour - plowing methods and planted trees as windbreaks.

30 Floods occur when there is more water than can be held by its banks. They occur during the wet seasons and during the spring snow melt. Scientists try to predict floods by studying the land and the amount of water in rivers and lakes.

31 Quick Check Summarize How can people protect the land from soil loss due to wind? We can protect soil loss by planting windbreaks and contour-plowing.

32 Critical Thinking Why is predicting when floods might occur important? Floods can cause widespread damage and loss of life. It allows people to prepare and/or evacuate.