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Community Ecology Interactions within communities of organisms Outline 1. Key concepts 2. Ecosystems and communities 3. Competition, Predation, Commensalism, Mutualism, 4. Key Terms 5. Conclusions Key Concepts: 1. A habitat is the type of place where individuals of a species normally live 2. A community is defined as an assemblage of species living close enough together for potential interaction. 3. Every species in the community has its own niche 4. Interactions among species influence the structure of a community Dominant species are those in a community that have the highest abundance or highest biomass (the sum weight of all individuals in a population). 5. 6. Keystone species exert an important regulating effect on other species in a community. 1 Ecosystems and communities • • • • • Ecosystem: all factors affecting an organism’s survival: abiotic and biotic Individuals of a species form populations living in a given habitat Several populations interact to form communities within a habitat Many communities + abiotic factors form an ecosystem Everything interacts! Each organism plays a special role within a community Competition Predation Commensalism Mutualism Competition Interspecific competition for resources can occur when resources are in short supply. There is potential for competition between any two species that need the same limited resource. The competitive exclusion principle: two species with similar needs for same limiting resources cannot coexist in the same place. 2 The ecological niche is the sum total of an organism’s use of abiotic/biotic resources in the environment. An organism’s niche is its role in the environment. The competitive exclusion principle can be restated to say that two species cannot coexist in a community if their niches are identical. Competition Resource Partitioning Three annual plants in a plowed field All require water and minerals but differ in adaptations 3 Niches and competition Predation A predator eats prey. Herbivory, in which animals eat plants. In parasitism, predators live on/in a host and depend on the host for nutrition. Predator adaptations: many important feeding adaptations of predators are both obvious and familiar. Claws, teeth, poison, speed, and agility. Predation Plant defenses against herbivores include chemical compounds that are toxic. Animal defenses against predators. Behavioral defenses include fleeing, hiding, self-defense, etc Camouflage Mechanical defenses include spines. Chemical defenses include odors and toxins Coloration is indicated by warning colors, and is sometimes associated with other defenses (toxins). Mimicry is when organisms resemble other species. 4 Parasites and pathogens as predators. A parasite derives nourishment from a host, which is harmed in the process. Endoparasites live inside the host and ectoparasites live on the surface of the host. Pathogens are disease-causing organisms that can be considered predators. Predation Ecosystem and Community Lions and their preys Camouflage Biston betularia Color Adaptation Contrast 5 Camouflage Commensalism Commensalism: an organism of one species benefits from its interactions with another; the other species neither benefits nor is harmed EX: epiphytes; barnacles; clownfish and anemones Mutualism A relationship where two species live together in close association, with benefits for both Frequently one species gets protection and/or support while the other gets food or a home or transportation 6 Mutualism Interspecific interactions Dominant species are those in a community that have the highest abundance or highest biomass (the sum weight of all individuals in a population). Keystone species exert an important regulating effect on other species in a community. 7 Predation Parasitism Mutualism Competition Competitive exclusion Mimicry Niche Camouflage Community Dominant species Keystone species In Conclusion 1. A habitat is the type of place where individuals of a given species normally live 2. Each species has its own niche in the community 3. Mutualism, commensalism, competition, and predation are species interactions that directly or indirectly link the populations in a community 4. Species that require the same limited resource tend to compete 8 In Conclusion 5. Predator adaptations: Claws, teeth, poison, speed, and agility. 6. Parasites and pathogens as predators. 7. Commensalism: an organism of one species benefits from its interactions with another; the other species neither benefits nor is harmed 8. Mutualism: A relationship where two species live together in close association, with benefits for both 9