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COMMUNITY ECOLOGY OBJECTIVES: • Describe types of relationships among organisms. • Compare primary and secondary succession. Community Interactions Community = a group of populations of different species living close enough to interact. Types of Interactions: • Competition, • Predation, • Symbiosis. Competition • The competitive exclusion principle states that when two species compete for the same resource or niche, eventually the one with the slight reproductive advantage will eliminate the other. Predation • A true predator kills and eats the other animals (prey). • A parasite spends most or all of its life living on another organism (host) and feeding on its tissues. • A herbivore is an animal that eats plants. Symbiosis Symbiosis = “living together”; several types: Mutualism = both species benefit. Parasitism = one organism benefits and the other is harmed. Commensalism = one organism benefits; the other is neither harmed nor benefited. Ecological Succession http://www.y outube.com/ watch?v=V4 9IovRSJDs Succession – gradual change in the composition of species over time; frequently following a disturbance. 1. Primary succession - succession on a new site by pioneer species such as lichens; eventually larger plants replace the pioneer species. Lichen = fungus living with algae or cyanobacteria (mutualism). Example: colonization after volcanic eruption. Primary succession 2. Secondary succession – changes occurring where soil and vegetation already exist. Example: gradual changes after a fire. Secondary succession • Climax community = stable, mature community that undergoes little succession. Hmm… 1. Does primary or secondary succession take longer? Why? 2. Are pioneer species r-selected or K-selected species? 3. How do species cause changes in the habitat that will result in different species composition? Species Diversity = measures the number of different species in a community and the relative abundance of each species. Dominant species have the highest biomass (the sum weight of all members of a population). Keystone species have a strong influence on the survival of other species; their removal results in dramatic changes in the makeup of species in a community. Keystone species examples: sea otter, grizzly bear, wolf. Invasive species: http://www.youtube.com/watch?v=HAY_UsGjyZk An introduced (non-native) species that may compete with native species for resources such as food, space, and water. Examples: tamarisk, zebra mussels, kudzu. Note: Most non-native species are not invasive. Hmm… • How do keystone species maintain balance in ecosystems? • How does the introduction of a non-native species influence the balance of an ecosystem? MATH CONNECTION The daily caloric requirements for male versus female killer whales (orcas) is shown below: • Male killer whale: 308,000 kcal/day • Female killer whale: 187,000 kcal/day Calculate the average caloric value of a sea otter assuming a male orca consumes five sea otters each day to meet its caloric requirement. Give your answer to the nearest hundredth.