Unit 2 Lesson 5 Human Activity and Ecosystems Copyright © Houghton Mifflin Harcourt Publishing Company

Growing Pains How do humans negatively affect ecosystems? Unit 2 Lesson 5 Human Activity and Ecosystems Growing Pains How do humans negatively affect ecosystems? An ecosystem is all of the living and nonliving things within a given area. Changing one thing in an ecosystem can affect many other things, because everything in an ecosystem is connected. Humans can affect ecosystems through pollution. Pollution is caused by any material or condition that harms the environment. Copyright © Houghton Mifflin Harcourt Publishing Company

How do humans negatively affect ecosystems? Unit 2 Lesson 5 Human Activity and Ecosystems How do humans negatively affect ecosystems? The growing human population has created a greater need for natural resources, leading to changes in ecosystems. The overuse of resources causes them to be depleted, or used up. Resource depletion occurs when a large fraction of a resource has been used up. Copyright © Houghton Mifflin Harcourt Publishing Company

How do humans negatively affect ecosystems? Unit 2 Lesson 5 Human Activity and Ecosystems How do humans negatively affect ecosystems? Compare the time it took for the human population to grow from 1 billion to 2 billion, and from 3 billion to 6 billion. Copyright © Houghton Mifflin Harcourt Publishing Company

How do humans negatively affect ecosystems? Unit 2 Lesson 5 Human Activity and Ecosystems How do humans negatively affect ecosystems? Human population growth in and around cities is called urbanization. Urban growth within ecosystems often destroys natural habitats and can bring humans and wildlife into contact. Every habitat has its own number and variety of organisms, or biodiversity. If a habitat is damaged or destroyed, biodiversity is lost. Copyright © Houghton Mifflin Harcourt Publishing Company

Water, Water Everywhere Unit 2 Lesson 5 Human Activity and Ecosystems Water, Water Everywhere How do humans impact oceans? Oceans support various ecosystems that together contain nearly half of Earth’s species. Pollution damages these ecosystems and threatens biodiversity. Point-source pollution comes from one source, such as an oil spill. Nonpoint-source pollution comes from many sources, such as when chemical fertilizers and pesticides are washed into oceans. Copyright © Houghton Mifflin Harcourt Publishing Company

How do humans impact oceans? Unit 2 Lesson 5 Human Activity and Ecosystems How do humans impact oceans? A greater demand for seafood from the growing human population has led to overfishing of some ocean species. If a fish population cannot reproduce fast enough, it may become locally extinct. The local loss of a species can disturb ocean food webs and threaten ecosystem stability. Copyright © Houghton Mifflin Harcourt Publishing Company

How do humans impact oceans? Unit 2 Lesson 5 Human Activity and Ecosystems How do humans impact oceans? The growing human population has led to increased coastal development and has increased pollution on shore and in coastal waters. In some places, development has almost completely replaced natural coastlines, destroying mangrove forests that protect coastlines. Human activity has also damaged coral reefs, but scientists and others are working to correct this damage. Copyright © Houghton Mifflin Harcourt Publishing Company

How do humans affect freshwater ecosystems? Unit 2 Lesson 5 Human Activity and Ecosystems How do humans affect freshwater ecosystems? In many river ecosystems, human activities have decreased the amount of water, or water quantity. Dams block the flow of river water, leading to less water downstream. If the natural course of a river is changed by channelization, it changes the water quantity, temperature, and chemistry. This affects river species. Copyright © Houghton Mifflin Harcourt Publishing Company

How do humans affect freshwater ecosystems? Unit 2 Lesson 5 Human Activity and Ecosystems How do humans affect freshwater ecosystems? Human activities can also decrease water quality, or how good the water is. Fertilizers contain nutrients that can enter ponds and lakes as runoff. An increase in the amount of nutrients, such as nitrates, in an aquatic ecosystem is called eutrophication. Excess nutrients in ponds and lakes cause overgrowth of algae, using up the pond’s dissolved oxygen and causing fish to die. Copyright © Houghton Mifflin Harcourt Publishing Company

How do humans affect freshwater ecosystems? Unit 2 Lesson 5 Human Activity and Ecosystems How do humans affect freshwater ecosystems? Water quality is also affected by air pollution. Burning fossil fuels releases chemicals into the air, and some of the chemicals combine with rain to produce acid rain. Acid rain can damage both aquatic and land ecosystems. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 2 Lesson 5 Human Activity and Ecosystems Exotic Species An organism that makes a home for itself in a new place outside its native home is an exotic species. Exotic species that outcompete native species are called invasive exotic species. When European rabbits were introduced into Australia, their population exploded because they had plenty of space and food, but no predators. Copyright © Houghton Mifflin Harcourt Publishing Company

Save It! How do humans protect ecosystems? Unit 2 Lesson 5 Human Activity and Ecosystems Save It! How do humans protect ecosystems? The careful and responsible management of a resource is called stewardship. The organisms in an ecosystem depend on each other and interact to form a vast food web. The loss of a species can leave gaps in the web. Humans can protect habitats and help species survive, thereby protecting the biodiversity and health of an ecosystem. Copyright © Houghton Mifflin Harcourt Publishing Company

How do humans protect ecosystems? Unit 2 Lesson 5 Human Activity and Ecosystems How do humans protect ecosystems? Conservation is the protection and wise use of natural resources. Practicing conservation means using fewer natural resources and reducing waste. It also helps prevent habitat destruction. There are “three Rs” for conserving resources: reduce what you buy and use; reuse what you already have; and recycle by recovering materials from waste. Copyright © Houghton Mifflin Harcourt Publishing Company