Ecological Relationships
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Name: ____________________________ Ecological Relationships All organisms are connected to each other in an ecosystem. Organisms form relationships with each other because they are connected. Some organisms compete against other organisms for resources or space. Other organisms depend on each other to survive. These relationships are called ecological relationships. Ecological relationships exist because of niches.A niche is an organism’s role in an ecosystem.A niche includes the physical space an organism occupies and how that organism interacts with other organisms in that space.A niche is also determined by the place the organism has in the food chain. Only one species can occupy a specific niche in an ecosystem. This allows different species to live together. It also stabilizes ecosystems. The interaction between organisms in similar or overlapping niches results in an ecological relationship. There are five types of ecological relationships. Competition is the contest between organisms for food, space, mates and other resources. Predation is when one organism feeds on another organism. Commensalism, mutualism and parasitism are types of ecological relationships as well. These relationships are forms of symbiosis. Symbiosis is a close and long term interaction between organisms. Competition There are limited resources in an ecosystem. Individuals compete for these resources and for space. This is called competition. Individuals of the same species compete with each other. They compete for food, water, mates and territory. Different species compete with each other for resources and space as well. Often species compete to live in the same habitat.A habitat is the area that an organism lives. Sometimes one species may be eliminated from the habitat.A species may be eliminated if two species are competing to occupy the same niche. Ecology 44 © Stephanie Elkowitz Ecological Relationships Continued Predation Predation is an important relationship between organisms. One organism feeds on another organism. The organism that is eaten is called prey. The organism that is eating is called the predator. Often, the prey is the predator to a different organism and the predator is a different organism’s prey! The predator-prey relationship creates a cyclic change in populations. When predators eat prey, the prey population decreases. The decrease in food for the predator limits the predator population. Therefore the predator population decreases. You will study this ecological relationship further in another activity. Commensalism Commensalism is a form of symbiosis. It is a relationship between two organisms where one organism benefits from the relationship. The other organism does not benefit from the relationship but is not harmed by it either. The relationship between barnacles and whales is an example of commensalism. Barnacles become mobile by attaching to the whale. They also are protected from predators. The whale is neither helped nor harmed by the barnacles. Mutualism Mutualism is another form of symbiosis. In mutualism, both organisms benefit from the relationship. There are many examples of mutualism in an ecosystem.A well-known example is between a fungus and alga. Together, these species form lichen. The alga performs photosynthesis and produces food. The fungus feeds on the food. The fungus retains water, which protects the alga. Lichen can survive in harsh environments where fungus and alga could not survive on their own. Parasitism Parasitism is the third type of symbiosis. In parasitism, one organism benefits from the relationship. This organism is called the parasite. The other organism is harmed, but not always killed. This organism is called the host. Ticks, fleas and intestinal worms are examples of parasites. Very often, the parasite does not kill the host. The parasite relies on the host and if the host dies, the parasite often dies as well. Many human diseases are caused by parasites. If the parasite grows large or overpopulates the human body, it will cause severe illness or death. Ecology 45 © Stephanie Elkowitz Name: ________________________ Predator-Prey Graphing Activity In this activity, you will study the predator-prey relationship between moose and wolves on the Isle Royale in Michigan. These organisms are isolated on a small island. There is little migration of animals in or out of the island. Furthermore, the wolves are the only predators of the moose and the moose are almost exclusively the prey for the wolves. These features create a unique example of predation. Many scientists study the Isle Royale moose and wolves since very few variables influence their relationship. Directions: Read the background information. Then graph the data. Answer the summary questions using data from the graph and information from the reading. Background Information Isle Royale is a small, forested island in the middle of Lake Superior in Michigan. The island is protected by national park status. Hunting and other human activities are prohibited on the island. The island was isolated until the early 1900s. Moose swam across Lake Superior from Minnesota to the island. There were no natural predators to the moose on the island. The forest service was concerned that without predators, the moose could overpopulate and consume all the resources on the island. The island flourished with vegetation, but every ecosystem food supply is limited. They feared overpopulation could cause overgrazing and then mass starvation of the moose. The moose population grew relatively unchecked until 1949, when a single breeding pair of wolves crossed an ice bridge from Ontario, Canada to the island. Scientists believed the wolves would populate the island and control the moose population. They would feed on the moose and prevent the moose population from becoming too large. Furthermore, the forest service believed the wolves would improve the overall health and quality of the moose herd. The predators would eliminate weaker members of the herd. Only strong individuals would survive, reproduce and pass their traits on to offspring. Scientists monitored the moose and wolf interactions. They kept track of changes in their population size. The table on the following page shows changes in the moose and wolf population from 1960 to 2010. *Background information and data from: http://www.isleroyalewolf.org Ecology 46 © Stephanie Elkowitz Predator-Prey Graphing Activity The table below shows the moose and wolf population on Isle Royale from 1960 to 2010. Use data in the table to create a graph. Use the guidelines below to help you. After you complete the graph, answer the summary questions. Isle Royale Moose and Wolf Population (1960-2010) YEAR # Moose # Wolves 1960 500 20 1965 750 28 1970 1500 17 1975 1200 42 1980 800 50 1981* 800 14 1985 1200 24 1990 1300 14 1995 2300 16 1996** 500 22 2000 800 28 2005 500 15 2010 700 20 You will create a line graph. Use the guidelines below to help you create the graph. • Use the left axis to help you plot the wolf population. • Use the right axis to help you plot the moose population. • Plot the points for wolf population size with an open circle or colored pencil. • Plot the points for moose population size with a closed circle or colored pencil. • Create a key to show which symbol or color you used for each population. Notes: *In 1981, humans accidentally introduced a canine virus that killed many wolves. **In 1996, there was an outbreak of moose ticks. Additionally, the winter was harsh and there was increased competition for food among the moose. Ecology 47 © Stephanie Elkowitz Wolf Population Size 20 30 40 50 10 0 1960 1965 1980 1970 Isle Royale Moose and Wolf Population (1960- Population Wolf and Moose Royale Isle 1975 YEAR 1985 1990 1995 2010) 2010) 2000 2005 2010 © Stephanie Elkowitz 2000 2500 1000 1500 0 500 Ke Size Population Moose y Predator-Prey Graphing Activity Summary Questions 1. The moose population increases from 1960 to 1970. What happens to the wolf population as a result of this increase in moose? __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ 2. The wolf population increases from 1970 to 1980. What happens to the moose population as a result of this increase in wolves? __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ 3. In 1981, humans accidentally introduced a canine virus to the wolf population. How did this affect the wolf population? How did it affect the moose? __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ 4. In 1996, there was an outbreak of moose ticks. The winter was especially harsh and food was scarce for the moose. How did this affect the moose population? How did it affect the wolves? __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ 5. What do you think would have happened if wolves had not been introduced to Isle Royale? __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ Ecology 49 © Stephanie Elkowitz.