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Chapter 54 Community Ecology Community Ecology • The study of the interactions between the species in an area. Interspecific Interactions • Interaction between species. • May be positive, negative, or neutral (in regards to fitness) • Ex: Predation Mimicry Competition Symbiosis Predation (+/-) • Predator and prey relationships. • Ex – Lynx and Hares Herbivory (+/-) • When an organism eats parts of a plant or algae. • Herbivore – may have special adaptations to find their prey. • Plants – may have adaptations to avoid being eaten. Predation/Herbivory • Often results in interesting defenses or adaptations. • Ex: • Cryptic coloration • Aposematic coloration Cryptic Coloration • A passive defense where the prey is camouflaged against its environment. Aposematic Coloration • The use of conspicuous colors in toxic or unpalatable organisms to warn off predators. poison arrow frogs Mimicry • Defense mechanism where the mimic has a resemblance to another species, the model. • Types: • Batesian • Müllerian Batesian Mimicry • Palatable species mimics an unpalatable model. Hawk moth larva Snake Müllerian Mimicry • Two unpalatable species resemble each other. Cuckoo Bee Yellow Jacket Competition • When two species rely on the same limiting resource. • Intraspecific competition usually more severe than Interspecific competition. • Why? Competitive Exclusion Principle • Predicts that two species with the same exact requirement cannot co-exist in the same community. • The better adapted species will survive and the less adapted will go extinct. Think, Pair, Share • Discuss if the Competitive Exclusion Principle explain the spacing of fast food restaurants on the “strip” in most towns. Ecological Niche • The sum of a species’ use of the biotic and abiotic resources in its environment is called the species’ ecological niche. • How a species “makes its living” in its ecosystem. • Species can not have niche overlap, the Competitive Exclusion Principle Niche Types 1. Fundamental - what a species is theoretically capable of using. 2. Realized - what a species can actually use. Think, Pair, Share • Again in terms of fast food restaurants, explain the concept of a fundamental vs. realized niche. Resource Partitioning • A way that species avoid niche overlap by splitting up the available resources. • Ex: Anolis lizards A. distichus A. insolitus Symbiosis • When two different species live together in direct contact. • Types: 1. Parasitism 2. Commensalism 3. Mutualism Parasitism (+/-) • Parasite harms the host. • Parasites may be external or internal. • Well adapted parasites don't kill the host. • https://www.youtube.com/watc h?v=uvdiYg6ZN-U Sci-Show Parasites Commensalism (+/o) • One partner benefits while the other is unchanged. • Ex. – Cattle and Egrets Mutualism (+/+) • Both partners Acacia Tree and Ants benefit from the interaction. • Ex: Pollinators and flowers Species with large impacts • Some species have larger impacts on a community structure than others. • Ex: • Dominant Species • Keystone Species • Foundation Species Dominant Species • A species that is the most abundant or has the highest biomass in a community. • Has a major effect on a community both biotically and abiotically. Reason for Dominance? • Best Competitor? • Best in avoiding predators and disease? • Invasive species may fit the last explanation. Example • Chestnuts – used to make up to 40% of the forest. • Lost between 1910-1950 because of fungus disease. • Major impact on wood and nut industries. Response • Some tree species increased in abundance to fill the gap. • Mammals and birds did OK. • 7 species of insects went extinct. Keystone Species • Not a dominant species, but has a major impact in the community structure. • Often a top predator that controls the numbers of other species. • Ex. Sea Otters Foundation Species • Species that cause physical changes in the environment that affect others. • Ex. Beavers, Bison, Black Rush • https://www.youtube.com/watc h?v=ysa5OBhXz-Q • How wolves change rivers Succession • Changes in species composition over time. Succession Stages • Climax Community - An ecological community in w hich populations of plants or animals remain stable and exist in balance with each other and their envi ronment. Succession Types 1. Primary 2. Secondary Primary Succession • Succession with only abiotic materials as the starting substrate • Ex: volcanic islands glaciated areas road cuts Secondary Succession • Succession with biotic materials (living or dead) as the starting substrate • Ex: • Cutting down a forest • Forest fire • Tornado/storm damage Steps of Succession • Pioneer Species – the first organisms to appear in the area in primary succession • Usually moss or lichens What do Pioneer Species Change? • Enrich the soil – as generations die, their remains decompose and add nutrients to the soil (often N). • The soil is now able to support a greater variety of species such as grasses and small shrubs. • Which occurs faster, primary or secondary succession? • What can you do to speed up succession? Point • If you understand the causes and controlling factors of succession, you can manipulate them. Some points about Succession • The Organisms are changing in the area over time. General pattern is an increase in biodiversity. • The Climate of the area is NOT changing over time. Other Changes • Soil – becomes richer in N, more depth, better water retention etc. • Light – can decrease at ground level because of shading by taller plants. Summary • Know the various types of interspecific interactions. • Know the Competitive Exclusion Principle and Niche Concept. • Know Species with large impacts. Summary • Know some examples and causes of succession.