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28 Cards in this Set
- Front
- Back
Community Ecology
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- Composition: how many species and which species
- Trophic network: who is eating whom? - WHo interacts w/ whome? - How important is competition and mutualism in determining the composition and trophic network in a community? - How do communities get started? What happens after disturbance? - succession |
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54.1 Community Interactions
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- INterspecific INteractions: include competition, predation, herbivory, symbiosis, and facilitation
- Predation is a +/- interaction: + effect for predator pop, - effect for prey pop - 5 types of interactions: competition, predation, herbivory, symbiosis, and facilitation strongly influence structure of communities - Mutualism: +/+ interaction, survival and reproduction of both species are increased in presence of one another - 0 indicates that pop is not affected by interaction in any known way |
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54.1 Community Interactions
- Competition |
- Interspecific Competition is -/-
- occurs when individuals of diff species compete for a resource that limits growth and survival - eg) weeds competing w/ garden plants |
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54.1 Community Interactions
- Competitive Exclusion |
- two species compete for limited resources
- two species competing for same limited resources can't coexist permanently in same place - one species will use the resources more efficiently and reproduce more rapidly than the other - eg) Paramecium aurelia, and Paramecium caudatum |
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54.1 Community Interactions
- Ecological Niches and Natural Selection |
- Sum of a species use of abiotic and biotic resources is called Ecological Niche
- Eugen Odum: if an organisms habitat is its addres, the niche is the organisms "profession" - how it fits into the ecosystem - competitive exclusion: two species can't coexist permanently in a community if their niches are identical - differentiation of niches that enables similar species to coexist in a community is called Resource Partitioning - Fundamental niche, niche potentially occupied by that species is diff from its realized niche, portion of its fundamental niche that it actually occupies. - testing the range of conditions in which it grows and reproduces in the absence of competition |
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54.1 Community Interactions
Predation |
- +/- interaction, predator kills and eats other prey
- predators have adaptations: claws, teeth, fangs, stingers, poison, ambush disguise - Prey also have adaptations: hiding, fleeing, forming herds, alarm calls - Cryptic Coloration, or camouflage makes prey difficult to see - Mechanical or chemical defense: porcupine, skunks, toxins - Aposematic Colouration: animals w/ chemical defense exhibit warning colours - Bastesian Mimicry: prey resemble other species. Harmless prey mimic dangerous predators (hawkmoth larva & green parrot snake) - Mullerian Mimicry: two or more unpalatable species, cuckoo bee and yellow jacket, resemble each other. - PRedators also use mimicry. Alligator snapping turtle wags tongue like a worm. |
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54.1 Community Interactions
Herbivory |
+ / - interaction, organism eats part of a plant or alga
- mammalian, invertebrate, and ocean herbivores - specialized adaptations: insects have chem sensors on feet to distinguish between toxic & non-toxic, sense of smell to examine plants, special teeth & digestive system - Plants defense: chemical toxins, thorns, spines, poison |
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54.1 Community Interactions
Symbiosis |
two or species live in direct and intimate contact w/ one another
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54.1 Community Interactions
Symbiosis: Parasitism |
+ / - interaction
- parasite derives nourishment from another organism - host is harmed in process - parasites live in body of host (tapeworms) - endoparasites - parasites feed on external surface (ticks, lice) - Ectoparasites - 1/3 of all species are parasites |
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54.1 Community Interactions
Symbiosis: Mutualism |
+/+ benefits both species
- flowering plants (nectare, fruit), animals (seed dispersal) |
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54.1 Community Interactions
Symbiosis: Commensalism |
- benefits one of the species, neither harms nor helps other (+/0)
- difficult to document |
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54.1 Community Interactions
Facilitation |
- can have positive effects + / + or 0/+ on survival and reproduction of other species w/out direct contact of symbiosis
- common in plant ecology (black rush juncus, makes soil more livable for others) |
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54.2 Diversity and Trophic Structure
SPecies Diversity |
- Species Diversity: variety of diff kinds of organisms that make up the community
> has 2 components 1) Species Richness: number of diff species in community 2) Relative abundance: of diff species, proportion each species represents of all individuals in community - Shannon Diversity (H) H = - (pA ln pA + pB ln pB + pC ln pC +...) A,B,C = species in community p = relative abundance of each species ln = natural logarithm - higher value of H = more diverse community |
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54.2 Diversity and Trophic Structure
Diversity |
- Higher-diversity communities are often more resistant to invasive species, which are organisms that become established outside their native range
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54.2 Diversity and Trophic Structure
Trophic Structure - food chain |
- Structure and dynamics of a community depend on feeding relationships between organisms - Trophic Structure of the community
- Xfer of food E, up trophic levels from its source in plants (primary producers) through herbivores (consumers) to carnivores (secondary consumers) eventually to decomposers - Referred to as a food chain |
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54.2 Diversity and Trophic Structure
Trophic Structure: food webs |
- Charles Elton, linked food chains together into food webs
- can be simplified in 2 ways 1) species w/ similar trophic relationships in a given community can be grouped into broad functional groups 2) simplify a food web for closer study is to isolate portion of the web that interacts very little w/ rest of community |
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54.2 Diversity and Trophic Structure
Trophic Structure: limits on food chain length |
- 2 reasons why food chains are short
1) Energetic Hypothesis: length of food chain limited by inefficiency of E transfer along chain - Biomass: total mass of all individuals in a pop. (eg: producer - 100 kg of plants can support 10kg of herbivore biomass) 2) Dynamic Stability Hypothesis: long food chains less stable than short chains. Pop. fluctuations. |
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54.2 Diversity and Trophic Structure
Species w/ a large impact |
- are highly abundant
- impact of these species occurs through trophic interaction |
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54.2 Diversity and Trophic Structure
Species w/ a large impact: Dominant Species |
- most abundant
- highest biomass - exert a powerful control over the occurrence and distribution of other species - way to discover impact, remove it from community |
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54.2 Diversity and Trophic Structure
Species w/ a large impact: Keystone species and Ecosystems |
- contrast to dominant species, Keystone Species
- not abundant - strong control on community structure - not by numerical might, but by pivotal ecological roles or niches - eg) sea star, maintaining diversity of an intertidal community - Species that dramatically alter their environment, ECOsystem Engineers - eg) beaver, could be + or - |
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54.2 Diversity and Trophic Structure
Species w/ a large impact: Bottom Up & Top Down Controls |
- Bottom Up: nutrients (N) > Plant (v) > Herbivore (H) > predator (P)
- about bottom controlling top - Top down Model: P > H > V > N - trophic cascade model eg) top down model to improve water quality in polluted lakes |
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54.3 Disturbance
- stability, disturbance, nonequilibrium model, |
- Stability is a communities tendency to reach and maintain relatively constant composition of species
- F.E Clements: biotic interactions caused the species in this climax community to function as an integrated unit - as a super-organism. - Viewed certain species of plants consistently around each other. - Disturbance: such as a storm, changes a community by removing organisms from it or altering resource availability - Non-equilibrium model - describes most communities as constantly changing after being affected by disturbances |
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54.3 Disturbance
- Characterizing Disturbance |
- storms disturb all communities, even ocean
- Fire - freezing lakes, rivers, ponds - flooding of streams and ponds - seasonal drying intermediate disturbance hypothesis - - moderate levels of disturbance foster greater species diversity than do low or high levels of disturbance. High levels of disturbance cause environmental stress |
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54.3 Disturbance
- Ecological Succession ecological, primary, secondary succession |
- Ecological Succession: disturbed area may be colonized by variety of species, gradually replaced by other species, replaced by still other species (continued pattern)
- Primary Succession: virtually lifeless area where soil hasn't formed yet. Only life forms initially present are autotrophic and heterotrophic prokaryotes. - Secondary Succession: existing community has been cleared by some disturbance that leave soil intact. |
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54.3 Disturbance
Human Disturbance |
- ecological succession is a response to disturbance
- strongest agent of disturbance is human activity: logging, agriculture |
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54.3 Disturbance
- Latitudinal Gradients |
- Charles Darwin & Alfred Wallace: life was more abundant and diverse in the tropics
- 2 key factors in latitudinal gradients of species richness (1) evolutionary history (2) Climate - Growing season in tropical forests, 5x as long as in tundra. (5x as fast) - Climate primary latitudinal gradient in richness and diversity - terrestrial communities, factors correlated w/ diversity are solar E input and water availability - These factors considered by measuring communities rate of Evotranspiration > evap of water from soil plus transpiration of water from plants. |
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54.5 Pathogens alter community structure locally and globally
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- Pathogens - disease-causing microorganisms, viruses, viroids,
- pathogens also influence community structure in terrestrial ecosystems - human activities are transporting pathogens, around the world fast (H1N1) |
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54.5 Pathogens
- Community Ecology and Zoonotic Diseases |
- 3/4 of human disease caused by zoonotic pathogens
- pathogens transferred to humans from animals - direct contact, infected animals , vectors (spread zoonotic disease - parasites, ticks, lice) |