Unit 2 Lesson 4 Changes in Ecosystems Copyright © Houghton Mifflin Harcourt Publishing Company
Nothing Stays the Same How quickly do ecosystems change? Unit 2 Lesson 4 Changes in Ecosystems Nothing Stays the Same How quickly do ecosystems change? Some changes happen slowly. With enough slow, constant change, a pond can develop into a meadow. Eutrophication is the process by which organic matter and nutrients slowly build up in a body of water. The growth and decay of organisms in the pond can fill it with organic material, which becomes soil. Meadow plants then grow in the soil. Copyright © Houghton Mifflin Harcourt Publishing Company
How quickly do ecosystems change? Unit 2 Lesson 4 Changes in Ecosystems How quickly do ecosystems change? Ecosystems can also change suddenly due to catastrophic natural events. The strong winds of a hurricane, a forest fire started by lightning, or a volcanic eruption can lead to massive destruction of an ecosystem. However, recovery brings new changes to an ecosystem. Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 4 Changes in Ecosystems Ruin and Recovery In 1980, the volcanic eruption of Mount St. Helens in Washington state killed people, plants, and animals, and damaged much forestland. The eruption changed the ecosystem dramatically. Trees fell, forests burned, ice and snow melted, and flowing mud removed more trees. Some species were protected by snow patches and ice, others were sheltered in burrows. As more sunlight reached the ground, seeds sprouted and the recovery began. Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 2 Lesson 4 Changes in Ecosystems Nothing Stays the Same What are the two types of ecological succession? The slow development or replacement of an ecological community by another ecological community over time is called succession. A community may start growing in an area that has no soil. This process is called primary succession. The first organisms to live in an uninhabited area are called pioneer species. They grow on rock and help form soil in which plants can grow. Copyright © Houghton Mifflin Harcourt Publishing Company
What are the two types of ecological succession? Unit 2 Lesson 4 Changes in Ecosystems What are the two types of ecological succession? Identify each step of primary succession. Copyright © Houghton Mifflin Harcourt Publishing Company
What are the two types of ecological succession? Unit 2 Lesson 4 Changes in Ecosystems What are the two types of ecological succession? Succession also happens to areas that have been disturbed but that still have soil. An existing ecosystem may be damaged by a natural disaster, or farmland may be cleared but left unmanaged. If soil is left intact, the original community may regrow through a series of stages called secondary succession. Copyright © Houghton Mifflin Harcourt Publishing Company
What are the two types of ecological succession? Unit 2 Lesson 4 Changes in Ecosystems What are the two types of ecological succession? What are the features of each stage of secondary succession shown here? Copyright © Houghton Mifflin Harcourt Publishing Company
It’s a Balancing Act What are two signs of a mature ecosystem? Unit 2 Lesson 4 Changes in Ecosystems It’s a Balancing Act What are two signs of a mature ecosystem? In the development of an ecosystem, a community of producers forms first, followed by decomposers and consumers. As a community matures, it may become dominated by well-adapted climax species. An ecosystem dominated by climax species is stable until it is disturbed. Copyright © Houghton Mifflin Harcourt Publishing Company
What are two signs of a mature ecosystem? Unit 2 Lesson 4 Changes in Ecosystems What are two signs of a mature ecosystem? As succession moves along, richer soil, nutrients, and other resources become available. This allows more species to become established. By the time climax species are established, the resources in the area support many different kinds of organisms. The number and variety of species that are present in an area is called biodiversity. Copyright © Houghton Mifflin Harcourt Publishing Company