Unit 3 Lesson 1 Earth s Support of Life. Copyright Houghton Mifflin Harcourt Publishing Company

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2 Living It Up What do living things need to survive? Earth is covered in living things. The basic necessities of life are air, water, a source of energy, and a habitat to live in.

3 How do Earth and the sun interact to support life on Earth? During photosynthesis, plants use the sun s energy, carbon dioxide, and water to produce oxygen and glucose. Plants form the foundation of many food chains. Some animals eat plants to gain energy. Other animals eat these animals.

4 How do Earth and the sun interact to support life on Earth? Earth s rotation allows most regions of Earth to receive sunlight regularly. Regular sunlight allows plants to grow in almost all places on Earth. Earth's rotation also protects areas on Earth from temperature extremes.

5 How do Earth and the sun interact to support life on Earth? Earth s distance from the sun also protects it from temperature extremes. Earth s temperatures range from below 0 C (32 F) to above 38 C (100 F), allowing life to survive in the coldest and hottest places on Earth.

6 How do Earth and the sun interact to support life on Earth? Which planet is too hot to support life. Which planet is too cold?

7 Water, Water Everywhere What is unique about Earth s water? As early Earth cooled, it released steam and other gases into the air. The steam formed clouds, water fell to Earth as rain, and Earth s oceans began. Also, icy comets and meteors impacted Earth and added water to Earth s oceans.

8 What is unique about Earth s water? How did Earth come to accumulate so much water on its surface?

9 What is unique about Earth s water? Earth is unique in the solar system because it contains water in the solid, liquid, and gas states. Most of the water is in liquid form. Liquid water is essential to life because cells need liquid water in order to perform life processes. Water remains a liquid on Earth because surface temperatures generally stay above the freezing point and below the boiling point of water.

10 Extremophiles Extremophiles are organisms that live in extreme environments. The Antarctic has ice-covered lakes and cold, dry valleys, but life can still be found there. A type of worm called a nematode survives in the cold by producing antifreeze in its cells. The presence of extremophiles on Earth makes it seem possible for life to exist in the extreme conditions on other planets.

11 Security Blanket How does Earth s atmosphere support life? An atmosphere is a mixture of gases that surround a planet, moon, or other space object. Some space objects have atmospheres, and some do not. It often depends on the strength of the object s gravity.

12 How does Earth s atmosphere support life? Earth s atmosphere is composed mainly of nitrogen and oxygen. It also has traces of carbon dioxide and other gases. Plants and some single-celled organisms use carbon dioxide for photosynthesis. Plants, animals, and most other organisms use oxygen to perform cell processes.

13 How does Earth s atmosphere support life? Earth s atmosphere was originally just hydrogen and helium. These gases, being very light, escaped into space. Volcanoes released water vapor, carbon dioxide, and ammonia into the atmosphere. Solar energy broke ammonia apart into nitrogen and hydrogen. Bacteria used carbon dioxide to perform photosynthesis, releasing oxygen into the atmosphere.

14 How does Earth s atmosphere support life? As the sun s radiation reaches Earth, some of it is reflected back into space, some is absorbed by atmospheric gases, and some is absorbed by Earth s surface. Earth's surface then radiates energy, which is absorbed and re-radiated by atmospheric gases through a process called the greenhouse effect. The greenhouse effect keeps Earth warmer than it would be if Earth had no atmosphere.

15 How does Earth s atmosphere support life? One type of solar radiation that can harm life is ultraviolet radiation. It can damage the genetic material in organisms. Earth has a protective ozone layer that blocks most ultraviolet radiation before it reaches Earth's surface. Each molecule of ozone is made up of three oxygen atoms. Some human-made chemicals have damaged the ozone layer.

16 How does Earth s atmosphere support life? What is the greenhouse effect? How does the ozone layer protect living organisms?