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BIOL 110: Final Exam
Ecology
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scientific study of the interactions between organisms and the environment
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Organismal Ecology
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studies how an organism's structure, physiology and (for animals) behavior meet environmental challenges
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Population Ecology
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focuses on factors affecting how many individuals of a species live in an area
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Community Ecology
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deals with the whole array of interacting species in a community
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Ecosystem Ecology
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emphasizes energy flow and chemical cycling among the various biotic and abiotic components
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Landscape
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mosaic of connected ecosystems
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Landscape Ecology
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deals with arrays of ecosystems and how they are arranged in a geographic region
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Biosphere
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global ecosystem, the sum of all the planet's ecosystems
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Global Ecology
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examines the influence of energy and materials on organisms across the biosphere
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Rachel Casron
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credited with starting the modern environmental movement with the publication of 'Silent Spring' in 1962
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Biotic
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living factors
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Abiotic
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nonliving factors
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Factors that determine distribution
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biotic and abiotic
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Dispersal
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movement of individuals away from centers of high population density of from their area of origin
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Community
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an assembly of populations of various species living close enough for potential interaction
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Interspecific Interactions
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relationships between species in a community
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Examples of Interspecific interactions
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competition, predation, herbivory, and symbiosis
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What does interspecific interactions affect?
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can affect the survival and reproduction of each species and the effects can be summarized as positive, negative or no effect
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Interspecific Competition
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-/- interaction; occurs when species compete for a resource in short supply
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Competitive Exclusion
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local elimination of competing species; strong competition can lead to this
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Predation
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+/- interaction; interaction where one species, the predator, kills and eats the other, the prey
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Feeding adaptations of predators
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claws, teeth, fangs, stingers, and poison
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Behavioral Defenses
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hiding, fleeing, forming herds and schools, self-defense, alarm calls and some morphological and physiological defense adaptations
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Cryptic coloration
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camouflage; makes prey difficult to spot
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Herbivory
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+/- interaction; a herbivore eats parts of a plant or alga
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Symbosis
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relationship where two or more species live in direct and intimate contact with eachother
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3 types of symbiosis
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mutualism, commensalism, parastitism
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Mutualism
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+/+ interaction; interspecific interaction that benefits both species
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Obligate (mutualism)
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one species cannot survive without the other
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Faculative (mutualism)
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where both species can survive alone
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Commensalism
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+/0 interaction; one species benefits and the other is apparently unaffected
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Why is commensal interactions hard to document in nature?
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any close association likely affects both species
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Parasitism
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+/- interaction; when one organism, the parasite, derives nourishment from another organism, its host, which is harmed in the process
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Endoparasites
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parasites that live within the body of their host
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Ectoparasites
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parasites that live on the external surface of their host
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Species diversity
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variety of organisms that make up the community
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Trophic structure
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feeding relationships between organisms in a community; key factor in community dynamics
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Food chain
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links trophic levels from producres to top carnivores
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Two fundamental features of a community structure
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species diversity and trophic structure
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Food web
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branching food chain with complex trophic interactions
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How can food webs be simplified?
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isolate a portion of a community that interacts very little with the rest of the community
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Can species play a role at more than one trophic level?
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Yes
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Limits on Food Chain Length
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is usually only a few links long
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Two hypotheses to explain food chain length
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energetic hypothesis and dynamic stability hypothesis
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Energetic hypothesis
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suggests that the length is limited by inefficient energy transfer
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Dynamic stability hypothesis
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proposes that long food chain are less stable than short ones
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Which hypothsis is most supported?
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most data supports the energetic hypothesis
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Types of species with a large impact
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dominant species, invasive species, keystone species, and foundation species
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Dominant Species
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those that are most abundant or have the highest biomass; exert powerful control over occurrence and distribution of other species
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Biomass
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total mass of all individuals in a population
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Hypothesis suggestions on dominant species
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most competitive in exploiting resources; most successful at avoiding predators
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Invasive species
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typically introduced to a new environment by humans, often lack predators or disease
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Keystone Species
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exert strong control on a community by their ecological roles, or niches; not necessarily abundant in a community
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Foundation species
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"ecosystem engineers" cause physical changes in the environment that affect community structure
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Facilitators
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some foundation species act as these; have positive effects on survival and reproduction of some other species in the community
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Bottom-up Model of community organization
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proposes a unidirectional influence from lower to higher trophic levels
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Top-Down model of community organization
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"trophic cascade model" proposes that control comes from the trophic level above; in this case predators control herbivores, which in turn control primary producers
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What determines community structure in bottom-up model?
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presence or absence of mineral nutrients, inlcuding abundance of primary producers
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Nonequilibrium Model
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describes communities as constantly changins after being buffeted by disturbances
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Disturbance
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an event that changes a community, removes organisms from it and alters resource availability
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Example of Disturbance
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fire- in most terrestrial ecosystems
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Intermediate Disturbance hypothesis
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suggests the moderate levels of disturbance can foster greater diversity than either high or low levels of disturbance
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Low levels of Disturbance
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allows dominant species to exclude less competitive species
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Two key factors that affect a community's species diversity
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latitude and area
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Species richness
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declines along an equatorial-polar gradient and is especially great in the tropics
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Climate
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primary cause of the latitudinal gradient in biodiversity
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Two climatic factors correlated with biodiversity
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solar energy and water availability; can be considered together by measuring a community's rate of evapotranspiration
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Evapotranspiration
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evaporation of water from soil plus transpiration of water from plants
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Species-area curve
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quantifies the idea that, all other factors being equal, a larger geographic area has more species
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Examples of species-area curve
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studies of species richness on the Galapagos Islands support the prediction that species richness increases with island size; USA- breeding birds supports this
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Pathogens
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effects ecological communities and their structures; inclide disease-causing microorganisms, viruses, viroids and prions
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What is transporting pathogens?
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human activities at unprecedented rates
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Zoonotic
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pathogens that have been transferred from other animals to humans
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How can pathogens be transfered?
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directly or through an intermediate species called a vector
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Ecosystem
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consists of all the organisms living in a community, as well as the abiotic facors with which they interact
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Range of ecosystems
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can range from a microcosm, such as an aquarium, to a large areas, such as a lake
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Ecosystem dynamics involve two main processes
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energy flow and chemical cycling
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Energy and matter in respect to ecosystems
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energy flows through while matter cycles within them
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First law of thermodynamics
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energy cannot be created or destroyed, only transformed
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2nd law of thermodynamics
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every exchange of energy increases the entropy of the universe
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Energy flow through ecosystem
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energy enters as solar radiation, is conserved, and is lost from organisms as heat; not always completely efficient
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Law of conservation of mass
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states that matter cannot be created or destroyed
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Chemical elements and ecosystems
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they are continually recycled through
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Forest ecosystem (conservation of mass)
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most nutrients enter as dust or solutes in rain and are carried away in water
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Autotrophs
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build molecules themselves using photosynthesis or chemosynthesis as an energy source
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Heterotrophs
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depend on the biosynthetic output of other organisms
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Energy and Nutrient Flow
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primary producers--primary consumers--secondary consumers--tertiary consumers
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Primary Producers
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autotrophs
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Primary consumers
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herbivores
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Secondary consumers
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carnivores
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Tertiary consumers
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carnivores that feed on other carnivores
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Detritivores
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"decomposers" are consumers taht derive their energy from detritus; ex: prokaryotes and fungi
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Detritus
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nonliving organic matter
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What connects all trophic levels?
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decomposition
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Secondary production
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amount of chemical energy in food converted to a new biomass during a given period of time
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Trophic efficiency
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percentage of production transferred from one trophic level to the next and it usually ranges from 5% to 20%
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How efficient is the energy transfer between trophic levels?
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10%
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What percent of chemical energy fixed by photosynthesis reaches a teritary consumer?
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0.10%
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Biogeochemical cycles
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nutrient circuits in ecosystems involve biotic and abiotic components and are called this
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Element cycle
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carbon, oxygen, sulfur and nitrogen occur in the atmosphere and cycle globally while elements sucj as phosphorus, potassium and calciumcycle on a more local level
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Carbon reservoirs
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include fossil fuels, soils and sediments, solutes in oceans, plant and animal biomass, and the atmosphere
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Nitrogen is a component of...
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amino acids, proteins, and nucleic acids
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Main reservoir of nitrogen
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atmosphere; through this it must be converted to NH4+ or NO3- for uptake by plants, via nitrogen fixation by bacteria
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How is organic nitrogen decomposed?
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decomposed to NH4+ by ammonification and NH4+ is decomposed to NO3- by nitrification
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Dentrification and Nitrogen
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converts NO3- back to N2
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Rates at which nutrients cycle in different ecosystems
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vary greatly, mostly as a result of differing rates of decomposition
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Rate of decomposition
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controlled by temperature, moisture, and nutrient availability
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Agriculture and chemical cycles on Earth
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removed from ecosystems nutrients that would ordinally be cycled back into the soil; nitrogen is main nutrient lost through agriculture
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What is used to replace lost nitrogen through agriculture?
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industrially produced fertilizer and effects on the ecosysyem can be harmful
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Critical load
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for a nutrient is the amount of plants can absorb without damaging the ecosystem
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The critical load is exceeded when...
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excess nutrients are added to an ecosystem
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Eutrophication
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excessive algal growth that can greatly harm freshwater ecosystems
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Acid precipitation
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pH less than 5.6
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Cause of acid precipitation
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combustion of fossil fuels
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Why are toxins harmful to the environment?
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become more concentrated in successive trophic levels
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Biological Magnification
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concentrates toxins at higher trohpic levels, where biomass is lower
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What are subject to biological magnification in ecosystems?
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PCBs (polychlorinated biphenyls) and many pesticides such as DDT
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Greenhouse effect
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CO2, water vapor, and other greenhouse gases reflect infared radiation back toward Earth
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What could cause global warming and climate change?
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increased levels of atmospheric CO2 are magnifying the greenhouse effect
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Where shows the strongest effect of global warming?
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northen coniferous forests and tundra
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How can global warming be slowed?
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reducing energy needs and converting to renewable sources of energy
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