1.3 Extracting Energy from Biomass Copyright © 2010 McGraw-Hill Ryerson Ltd. Although not all organisms undergo photosynthesis, all organisms— from single-celled bacteria to complex, many-celled life forms—get energy from glucose. Cellular respiration is a process that releases energy from organic molecules, especially carbohydrates, in the presence of oxygen. Fermentation also releases energy but in the absence of oxygen. (Page 28)

Extracting Energy from Food Copyright © 2010 McGraw-Hill Ryerson Ltd. In cellular respiration, organisms take in oxygen, which reacts with the glucose in cells to produce carbon dioxide, water, and energy. During the day, plants produce glucose through photosynthesis. At night and during the day, plants extract energy from the glucose using the process of cellular respiration. (Page 29)

Reviewing Photosynthesis and Cellular Respiration Copyright © 2010 McGraw-Hill Ryerson Ltd. Click the “Start” button to review the connection between photosynthesis and cellular respiration in plants.

Carbon Dioxide and Other Greenhouse Gases Copyright © 2010 McGraw-Hill Ryerson Ltd. Greenhouse gases are atmospheric gases that prevent heat from leaving the atmosphere, thus increasing the temperature of the atmosphere. The greenhouse effect is the warming of Earth as a result of increased greenhouse gases that trap heat energy that would otherwise leave Earth. Carbon dioxide (CO 2 ) is the most common of the greenhouse gases. (Page 29)

Biomass and Fossil Fuels Copyright © 2010 McGraw-Hill Ryerson Ltd. Because fossil fuels come from biomass that was produced by photosynthesis millions of years ago, burning them has an effect very similar to cellular respiration. They both produce large quantities of carbon dioxide (a greenhouse gas) that may contribute to global warming. (Page 30)

Reducing Carbon Dioxide in the Atmosphere Copyright © 2010 McGraw-Hill Ryerson Ltd. (Page 31)

Learning Check Copyright © 2010 McGraw-Hill Ryerson Ltd. 1. Explain the process of cellular respiration. 2. Describe the greenhouse effect. 3. Make a list of actions you could take to reduce the amount of carbon dioxide being released by the burning of fossil fuels. 4. As you write your answers to questions, using either a pen or a keyboard, you are using energy. Draw a flowchart that traces this energy back to the Sun. Activity 1-3 Recycling in Ontario (Page 31)

Fermentation, Methane, and Landfills Copyright © 2010 McGraw-Hill Ryerson Ltd. Methane (CH 4 ) is produced by bacteria when they break down organic waste using fermentation. Landfills, dumps, and swamps can produce large amounts of methane. Methane produced by bacteria in landfills can be captured, processed, and then burned to generate electricity for use in homes and businesses. (Page 32)

Acid Precipitation Copyright © 2010 McGraw-Hill Ryerson Ltd. In addition to producing greenhouse gases when burned, fossil fuels also produce undesirable compounds such as nitrogen oxide (NO X ) and sulphur dioxide (SO 2 ) that combine with water in the air to form nitric and sulphuric acid. These compounds contribute to acid precipitation, which is rain, snow, or fog that has a pH less than 5.6. (Page 33)

Measuring pH Copyright © 2010 McGraw-Hill Ryerson Ltd. A substance’s pH is an indication of how acidic or basic it is. The pH scale ranges from 0 to 7. Substances with a pH: lower than 7.0 are considered acidic equal to 7.0 are considered neutral greater than 7.0 are considered basic (Page 34)

Effects of Acid Precipitation Copyright © 2010 McGraw-Hill Ryerson Ltd. Continued exposure to acid rain can remove soil nutrients such as calcium and increase the level of soil nutrients such as aluminum. These changes can lead to the death of trees and, thus, the loss of forests. Acid precipitation is even more devastating to aquatic ecosystems. Many aquatic organisms have a very low tolerance to changes in the pH of the water they live in. (Page 34)

Reducing Acid Precipitation Copyright © 2010 McGraw-Hill Ryerson Ltd. Acid precipitation remains a problem, but the situation seems to be improving. Agreements between Canada and the United States plus new laws have reduced the level of cross-border pollutants. Through the use of scrubbers to remove undesirable gases from industrial emissions and with higher standards for motor-vehicle emissions, acid precipitation has been reduced since the 1980s. (Page 35)

Section 1.3 Review Copyright © 2010 McGraw-Hill Ryerson Ltd. Concepts to be reviewed: How do organisms use cellular respiration and fermentation to extract energy from glucose? How has the burning of fossil fuels affected the concentrations of greenhouse gases in the atmosphere? What is acid precipitation? What causes it? How does it affect living things? What measures have been taken to reduce acid precipitation? (Page 36)