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Community and Ecosystem Ecology. Chapter 38. Community Ecology. Species living in same vicinity Potential interactions will occur Interspecific interactions Interactions between species Classified according to effect on populations Helpful (+) Harmful (-). Community Interactions.
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Community and Ecosystem Ecology Chapter 38
Community Ecology • Species living in same vicinity • Potential interactions will occur • Interspecific interactions • Interactions between species • Classified according to effect on populations • Helpful (+) • Harmful (-)
Community Interactions • Occurs in a few ways: • Competition • Mutualism • Predation • Herbivory • Parasites and pathogens
1. Competition (-/-) • Occurs when members of two different species try to utilize the same resource • Competitive Exclusion Principle: • No two species can occupy the same ecological niche at the same time
Competition • Competition can lead to resource partitioning • decreases competition between the two species • Character displacementis often viewed as evidence that competition and resource partitioning have taken place
2. Mutualism (+/+) • Both members of the association benefit
3. Predation (+/-) • Predator • Prey • 2 ways this regulates population growth: • A. Predator-Prey Population Dynamics • B. Antipredator Defenses
3. Predation • A. Predator-Prey Population Dynamics • Cycling of predator and prey populations • Occurs when either predators overkill prey, or when prey overuse resources and their numbers crash • In either case, predator numbers also decrease from a decrease in food source
Coevolution • Evolutionary change in one species results in an evolutionary change in the other • Organisms in symbiotic associations are especially prone to the process of coevolution • Also occurs between predators and prey • Example: Cheetah sprints forward to catch prey, and this behavior might be selective for those gazelles that jump high in the air
3. Predation • B. Antipredator Defenses • Cryptic coloration • Camouflage • Warning coloration • Association with undesirable consequences
3. Predation • B. Antipredator Defenses • Mimicry • One species resembles another species • Can help capture food or avoid being preyed upon • Batesian Mimicry • A prey that is not harmful mimics another species that has a successful antipredator defense • Warning colorations • Mullerian mimicry • Species that resemble each other all have successful defenses
Mimicry Among Insects Mullerian Batesian
Coral snake vs. Milk snake http://www.youtube.com/watch?v=LU8DDYz68kM
4. Herbivory (+/-) • Consumption of plants by an animal • Plant must expend energy to regenerate • Evolved defenses
5. Parasites & Pathogens (+/-) • Parasite • Lives on or in a host • Endoparasite • Ectoparasite • Pathogens • Disease-causing microorganisms
Trophic Structures • Feeding relationships among species in a community • Determines the passage of energy and nutrients • Sequence of food transfer is a food chain • Unbranched
Trophic Structure • Autotrophs (producers) • Require an energy source and inorganic nutrients to produce organic food molecules • Manufacture organic nutrients for all organisms • Green plants and algae carry on photosynthesis
Trophic Structure • Heterotrophs (consumers) • Need a preformed source of organic nutrients • Herbivores • Graze directly on plants or algae • Carnivores • Feed on other animals • Omnivores • Feed on both plants and animals
Trophic Structure • Heterotrophs • Decomposers • Heterotrophic bacteria and fungi • Break down nonliving organic matter • They release inorganic matter to be used by producers • Scavengers • Feed on dead remains
Ecosystem Ecology • Possesses both abiotic and biotic components • Biotic • The various populations of organisms that form a community • Abiotic • Includes resources such as sunlight, inorganic nutrients, soil, water, temperature and wind • Two major processes sustain all ecosystems: • Energy flow • passage of energy through the components of the ecosystem • Chemical cycling • use and reuse of chemical elements within the ecosystem
al c cy i cl m e in g Ch Energy flow Chemical energy Light energy Heat energy Chemical elements Bacteria, protists, and fungi
Energy Flow • Biomass • Mass of living organic material in ecosystem • Ecological Pyramids • only about 10% of the energy of one trophic level is available to the next trophic level • Producers at the base • Most available energy • Energy is given off in less usable forms as producers are eaten by primary consumers, etc.
Chemical Cycling • Biogeochemical cycles • Biotic and abiotic components of the chemical cycles in an ecosystem • 3 main cycles: • Carbon cycle • Phosphorus cycle • Nitrogen cycle
CO2 in atmosphere Burning Photosynthesis Cellular respiration Higher-level consumers Plants, algae, cyanobacteria Primary consumers Wood and fossil fuels Decomposition Wastes; death Plant litter; death Decomposers (soil microbes) Detritus Figure 20.32