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What is a species composition?
What species a community contains and the relative abundances of those species
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What is the only way a species can occur in a location?
Only if it is able to colonize and persist there
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What does a community contain?
Species that are colonized those that are extinct LOCALLY
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What are some reasons extinctions can occur?
Small population, exclusions (predators, pathogens, competitors), lacking of a resource, species cant tolerate the local conditions
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What are factors that make species composition vary?
Environmental gradients, disturbances, and changing climate, elevation, soil type
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What is atransect?
A straight line used for ecological surveys that shoes species turnover through space
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What factor depends on the animals ability to get food or avoid predators?
Habitat Structure
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How can species turnovers result? What are some examples?
Disturbance events; volcanic eruptions, wildfires, hurricanes, landslides, human activities.
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What is succession?
The process by which species replace one another in a predictable sequence
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What can happen to a community after a disturbance?
It can undergo succession which leads to a community that resembles the original one
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If the original community is not reestablished after a disturbance, what happens?
It undergoes ecological transition.
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What is a niche?
The environmental tolerances of a species which define WHERE it can live; and it also refers to the ways a species obtains energy and materials and to patterns of interactions with other species in the community
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What are primary producers? What are they also known as?
Autotrophs. They convert solar energy into a form that can be used by the rest of the community.
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What are heterotrophs?
Organisms that get energy by breaking apart organic compounds that were assembled by other organisms.
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What are primary consumers?
Organisms that eat primary producers. Herbivores
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What are secondary consumers?
Eat primary consumers (carnivores)
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What are tertiary consumers?
Eat secondary consumers
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What are quaternary consumers?
Eat tertiary consumers
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What are omnivores?
Feed from multiple trophic levels
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What are decomposers? What is another term?
Detritivores. Feed on waste products or dead bodies of organisms
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What are decomposers responsible for?
Recycling materials and breaking down organic matter into inorganic components for primary producers to reabsorb.
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How are trophic interactions shown in diagram form?
Food webs
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GPP
Gross product productivity. The total amount of ENERGY that primary producers convert to chemical energy
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NPP
Net primary productivity. Energy contained in tissues of the primary producers and is available for consumption
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What is an approximation for NPP?
Change in biomass of primary producers (dry mass) per unit of time
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What is the ecological efficiency?
10%
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Why is ecological efficiency low?
Not all biomass ingested by next trophic level, some injected matter is indigestible so the animal poops it out, and organisms that use a lot of the energy they make to fuel their own metabolism
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What is the per capita growth rate related to?
The sum of positive and negative contributions of species with which it interacts
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What is species richness?
The number of species in the community
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What is species evenness?
The distrubtion of species abundances
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What aspects of diversity affect community function?
Species richness and evenness
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What are communities defined by?
The species that are more abundant than the rare ones
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What are important measures of community function?
GPP and NPP
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What are some possible reasons that species diversity affects community function?
Sampling, niche complementarity
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What is sampling?
Wen communities have many types of species, they are more likely to have some species with a very strong influence on community output
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What is niche complementarity?
Communities with many species can be better able to use all the available resources
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What are plant functional groups?
Plant groups that differ in traits such as ability to grow in warm vs cool weather, association with Nitrogen fixing bacteria, allocation to growth vs reproduction, etc.
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Where does the greatest diversity of plants and animals take place?
Tropics
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Why do the tropics support more species?
Maybe because the climate is so stable and hasnt been affected by glacial cycles; they have higher abundant solar energy and productivity, environmental heterogeneity.
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What does environmental heterogeneity mean?
That diversity is higher in more structurally COMPLEX habitats
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Who formulated the theory of island biogeography?
Macarthur and Wilson
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Why does habitat fragmentation cause loss of species?
Populations become smaller, amount of habitat decreases, average patch size decreases, patches become more isolated, human modified habitat can be a barrier to dispersal
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How do you enhance colonization in fragmentation?
Cluster habitat fragments and connect them with dispersal corridors
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How do your educe extinctions in fragmentation?
Keep a large patch of the original habitat.
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