Chapters 4 - Spokane Public Schools

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CHAPTER 5: ECOSYSTEMS Pollutants What is a pollutant Sulfur dioxide is a pollutant Mercury is a pollutant Human activities affect ecosystems in both positive and negative ways. One negative effect is pollution. A pollutant is something that causes harm to a living thing. Three things often determine how harmful a pollutant is: 1. the pollutant’s ability to cause harm 2. the amount of pollutant in the air, water, or soil 3. how long the pollutant stays in the air, water, or soil Sulfur dioxide is a chemical that is a good example of a pollutant (Figure 5.8). When sulfur dioxide is present in large amounts in the air, it can make breathing difficult even for healthy people. It also reacts with water in the atmosphere to make acid rain. Acid rain can kill trees and harm life in lakes, ponds, and streams. Sulfur dioxide enters the air from fossil fuel power plants, automobiles, and even volcanoes. Mercury is an element that can be found naturally in an ecosystem. Human activities like industry also cause the release of mercury into the environment. It is taken in by members of an ecosystem and it builds up in their bodies. When the amount of mercury in a living organism gets high enough, the animal or plant can be harmed and may even die. Mercury is commonly found in fish. Because mercury is stored up in the fatty tissues of the fish over its entire lifetime, the level of the mercury in the fish may be thousands of times higher than the level of the mercury in the water. This process, known as biomagnification, is explained on the next page. pollutant - a variable that causes harm to an organism. Figure 5.8: Sulfur dioxide is a pollutant. 5.3 ECOSYSTEMS—A NATURAL BALANCE 97
Toxins in the food chain What are toxins Human activities sometimes create toxic pollutants (toxins). High concentrations of toxins may impact living things. Toxins can cause slowed growth, decreased reproduction, and even death. When toxins enter ecosystems, they spread out and become less concentrated. Some toxins end up in lakes and oceans (Figure 5.9). Food chains concentrate some toxic pollutants, like mercury, into the tissues of animals. To understand how this happens, let’s look at a marine food chain. Figure 5.9: Some power plants send mercury into the air. This eventually falls to Earth with the rain and ends up in lakes and oceans. Concentration of toxins Toxins can be passed on to offspring Toxins are concentrated at each link in a food chain. As producers make food, they absorb molecules of toxins from the water. Next, herbivores eat large numbers of producers. Toxins like mercury dissolve in fat, not water. They are stored in the fatty tissues of herbivores and are not passed out of their bodies. When carnivores eat many herbivores, they accumulate even higher levels of toxins in their tissues. Secondary carnivores, who prey on other carnivores, can accumulate dangerous levels of toxins. These toxins can sometimes be passed on to their young. Figure 5.10 shows how the amount of a toxin can multiply as it travels up the food chain. Figure 5.10: The pyramid shows how toxins are concentrated at each link in a food chain. 98 UNIT 2 ORGANISMS AND THE ENVIRONMENT
Page 1 and 2: E Organisms and the Environment Cha
Page 3 and 4: 4.1 Elements and Compounds In the 1
Page 5 and 6: Chemical reactions What are chemica
Page 7 and 8: 4.1 Section Review 1. What are the
Page 9 and 10: Carbohydrates, fats, and proteins F
Page 11 and 12: Nucleic acids What are nucleic acid
Page 13 and 14: 4.3 Physical Variables You have rea
Page 15 and 16: Sunlight Type of soil Oxygen Sunlig
Page 17 and 18: The oceans Chemicals in ocean water
Page 19 and 20: Chapter 4 Connection Chef or Scient
Page 21 and 22: Chapter 4 Activity Scientists have
Page 23 and 24: Section 4.3 8. Name a habitat where
Page 25 and 26: 5.1 Ecosystems, Energy, and Nutrien
Page 27 and 28: Producers, consumers, and decompose
Page 29 and 30: The water and carbon-oxygen cycles
Page 31 and 32: 5.2 Food Chains and Food Webs All l
Page 33 and 34: Food webs What is a food web Most a
Page 35 and 36: 5.3 Ecosystems—a Natural Balance
Page 37: Invasive species Organisms interact
Page 41 and 42: More water quality tests Dissolved
Page 43 and 44: Chapter 5 Connection Food Webs of t
Page 45 and 46: Create a Species Chapter 5 Activity
Page 47 and 48: Section 5.2 Math and Writing Skills
Page 49 and 50: 6.1 Climates and Biomes Imagine som
Page 51 and 52: Other variables that affect climate
Page 53 and 54: Plants and animals in biomes Commun
Page 55 and 56: 6.2 Deserts and Grasslands In this
Page 57 and 58: Grasslands Grasslands are found on
Page 59 and 60: 6.2 Section Review 1. What is the m
Page 61 and 62: Tropical rainforests Tropical rainf
Page 63 and 64: 6.3 Section Review 1. How many seas
Page 65 and 66: Taiga life Snow keeps things warm!
Page 67 and 68: Permafrost stores carbon dioxide Pe
Page 69 and 70: Ecological Impact of Forest Fires C
Page 71 and 72: Chapter 6 Activity Biome Expedition
Page 73 and 74: 10. How is a temperate grassland li

Chapters 4 - Spokane Public Schools

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