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Transcript
3.2 Interactions and Changes Occur in Ecosystems Science 7 Unit A Key Terms Bioinvasion Competition predation predator prey Wetlands Case Scenario –p 55 • Read p. 55 • What makes wetlands special? • What do you think happened to make people reconsider the importance of wetlands? Give It a TRY - TO CHANGE OR NOT TO CHANGE Purpose To infer how an ecosystem will change over time. All things change! –p. 56 • Change is a factor for all life and for all ecosystems on Earth. • The cycles of matter that they have already studied illustrate constant change. • What are examples of changes that are happening inside you and around you? Make your own definitions: • After reading about the following terms, define in your own words: • Bioinvasion • Competition • Predation This is real; This is Nature! • In natural communities, living things compete with each other all the time. • Living things are trying to survive and are looking for the resources they need to do so. • When you have a limited number of resources, and many different species who need those resources, there is competition. INQUIRY ACTIVITY Survival in the Field Purpose To explore how competition might affect the health and survival of a population. Predation –p 60 • Read paragraph and think of other examples of predator-prey relationships. • Look at the photo of the flooded alfalfa field on this same page (by the Check and Reflect.) Think about a situation where weather has affected ecosystems. What are some of your thoughts? C & R –p. 60 • Do all questions. Answers to C & R –p. 60 The introduction of a non-native plant or animal is called bioinvasion. Bioinvasion can have serious consequences on ecosystems. Often these introduced species are stronger than the native species or they do not have any natural predators in their new environment. This means that they compete directly with native species for the available resources. Populations of native species are often reduced and sometimes eliminated. Answers to C & R –p. 60 2. a) The introduction of a new species can reduce populations of native species due to competition for resources, particularly food. Sometimes this competition leads to the elimination of the native species so this changes the community. b) If the availability of food decreases, then this may severely decrease some or most of the populations; the competition for food becomes more difficult. Answers to C & R –p. 60 3. You should notice the close relationship between the predator (lynx) and prey (hare) populations. When the hare population increases, there is lots of food for the lynx to feed their young, so the young survive. As the hare population increases, eventually they outstrip their food supply. Their population declines because of starvation as well as lynx predation. As the hares decline, there is less for the lynx to eat and they start to die of starvation. When the hares are at their lowest level, their food source can recover and there is more food for the remaining hares, so the cycle starts again. The lynx-and-hare population cycle is very well known. Students might like to know that scientists discovered this cycle by looking at records of lynx pelts bought by the Hudson’s Bay Company in northern Canada between 1845 and 1935. Review Key Terms Bioinvasion Competition predation predator prey