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How has sea level changed throughout the history of the earth?
- snowball earth theory=600 million years ago, the earth was completely frozen
- cold climate=low sea level
- Denver was a tropical rainforest about 60 million years ago
- oscelate between cool&warm periods(ice ages)
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Milankovitch cycles
- Related to what happens to the earth as it revolves around the sun, causes of climate change
- Eccentricity of orbit=orbit changes from elliptical to circular every 100,000 years
- Tilt of axis=goes from 22-24.5, happens every 40,000 years
- Wobble=short term change in global climate, earth is directly pointing to the sun, happens every 10-100 thousand years
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Megafauna extinction
- Drop-off of animals
- Not long after humans arrived, the animals were gone.
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community
- a group of populations of plants and animals in a given place and time
- or association of interacting species inhabiting some define area
- HAS TO BE LIVING!
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succession
- the developmental process that a community goes through, disturbances tend to reset succession
- changes physical and species make-up of that environment
- disturbances reset succession to get back to the pioneer environment
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primary succession
- succession from an area that has not been previously occupied
- no seed bank, no soil, no lichens, no nitrogen fixers
- bare rock, or volcanic islands
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secondary succession
- the re-establishment of a community following a disturbance that does not remove everything to bare rock
- seed bank, trunk regeneration, or mature soils
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facilitation
- when a species makes it more likely that another species will colonize the community
- lichens
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inhibition
- when a species makes it less likely that another species will colonize the community
- predator
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pioneer community
an early sere(stage) of succession with a high degree of r-selected species
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climax/mature community
- the final sere of succession with a high degree of k-selected species
- changes little ones it is reached, until a disturbance resets the succession
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mixed community
intermediate seres characterized by r and k selected species, or species with intermediate traits along the r-k continuum
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F.E. Clement's: balance of nature view of communities
all species living together in an organized, systematic manner to form a super organism
- communities even evolved in a way analogous to species over millions of years
- succession is like organismic development to get to final sere(oak forests became oak forests just as organisms becomes adults)
- -in equilibrium= each species does its part(balance)
- -saturated with species= all parts present
- -strong biotic interactions= predation in harmony
- -resource limited&optimal performance= used completely
- -deterministic= same endpoint where started
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H.A. Gleason view of communities
- history, chance, and randomness are important in community structure.
- a community isn't a super organism, but haphazard of organisms that have the same interests
- after cutting an oak forest, a pine forest returns
- a community is a fortuitous association of organisms whose adaptions allowed them to live together under the particular physical and biological conditions that characterize a particular place
- -nonequilibrium
- -many open niches, random
- -abiotic stresses are important(storms, droughts, fires)
- -opporutnism, new species come in
- -stochastic effects
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Clements vs. Gleason
- clements=same range
- gleason=not same range, real world, more accurate
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Food webs
- trophic relationships within a community
- lots of trophic levels=lots of odd plants
- even # of trophic levels=not a lot of plants
- simplified food web=more numerous, important, and more interacting species
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keystone species
- any species that has a greater impact on community structure than one would predict from it's abundance/biomass
- if keystone species reduce likelihood of competitive exclusion, their activities would increase the number of species that could coexist in communities
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Examples of keystone species
- Sea stars made the shallow subtidal diverse, with no seastars present mussels took over, species richness dropped without sea stars
- Sea otters eat urchins which eat kelp, when sea otters were removed bc of overhunting, kelp forests disappeared. Sea otters control urchin population which allows kelp to thrive.
- Kelp&corals have a large biomass, but a large impact(not keystone)
- Clownfish have a low biomass and a small impact(not keystone)
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Trophic cascade
- when the impact of a top trophic level cascades down to lower trophic levels
- flow from high to low
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Direct trophic effect
- influence of one species on another through immediate interaction
- orca eating sea otter
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Indirect trophic effect
- influence of a species on another species in a roundabout matter, mediated by a change in population size of a third intermediate species
- orcas indirectly influence kelp
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Higher order interaction
- influence of a species on another species in a roundabout manner, mediated by a change in behavior of a third intermediate species
- change in behavior
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Fish as a river keystone species
- Removing fish will increase plant abundance
- Keeping fish decreases plant abundance
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How do you study competition?
- remove exploitive species
- example=sea stars eat barnacles&mussels, mussels are a competitive dominant species, barnacles and seaweed compete, chitin eats seaweeds, and welks eat barnacles
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Exotic predators
- exotic species have dramatic impacts on communities because they were outside the evolutionary experience of local prey
- nile perch-government introduced exotic fish predator to lake victoria, fish fauna dramatically reduced. the food web was simplified with the new fish.
- many problems with this fish, it was too big to catch, had to cut down forest to smoke it, dissolved oxygen concentrations decreased, and cultural eutrophication.
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Oppossum shrimpi(flathead lake)
- introduced oppossum shrimp to lake to increase profit
- increased amount of trout because trout eats oppossum shrimp
- example of scaling
- oppossum shrimp ate zooplankton then hid
- became competitors with trout.
- trout died=no fishermen, no eagles=no money
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Toxins in food webs: DDT
- DDT=ideal pesticide, cheap, persistent, soluble in diesel fuel, highly toxic to insects, but non toxic to people
- developed prior to WWII, widespread use, banned in USA now
- found in inuit breast milk
- almost 2 million tons produced throughout history, 5000 tons still used
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Problem with long food webs
- bioaccumulation=storage of chemicals in adipose tissue
- biomagnification=increase in pollutant concentration as you move up the foodweb
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Successful with pesticides?
- Before pesticide use, about 30-35% of crops were lost to pests
- After decades of persistent use of pesticides, the same percent was still lost to pests.
- Some pesticides kills herbivores and predators, but herbivores adapt easier
- Humans have exposed ourselves and nature to many poisons with untested consequences
- Gain no agricultural benefit
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Alternative to pesticides
- Biological control=the use of living organisms to control the population size of pest usually with predation or parasitism
- Many pests are exotic species
- Classical biological control=going to the pest's native range to find a predator&treating an exotic species with a different exotic species
- Conservation biological control=control of exotic pest using a native biocontrol agent
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Biocontrol using a specialist
- Can be a good idea
- Example: prickly pear and moths in australia, too many rabbits, introduced virus to rabbits
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Biocontrol using exotic generalist predators
- A bad idea
- Example: introduced frog but it eats everything, can't get rid of it
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Biocontrol using native generalist predators
- A great idea
- good because its native
- praying mantis&ladybug controls pests
- Birds of prey control rodents
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Integrated pest management
- The application of ecology to manage the population sizes of pests
- Uses a variety of tools
- -chemicals are used judiciously, apply little
- -trap crops, plants an area of crop early to attract pests and spray them
- -biocontrol agents are encouraged, ladybugs/spiders
- -crop rotation returns
- -monocultures replaced with polycultures, crop rotations
- -sterile males, no eggs/reproductive failure
- -vacuums instead of tractors
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Disturbance and diversity in the Intertidal zone
- Sousa studied effects of disturbance on diversity of algae and invertebrates growing on boulders in the intertidal zone
- Predicted level of disturbance depends on boulder size, large boulders require more force to move
- Boulders supporting greatest diversity of species were those subject to intermediate levels of disturbance=consistent with intermediate disturbance hypothesis
- Size of boulder represented the degree of disturbance
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Island area&species richness
Richness correlated with island/lake size
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Island biogeography theory
- looks at how island properties affect species richness
- chances of colonizing is greater when richness is low because of open niches
- immigration is high when richness is low
- few species=low extinction, more species=greater extinction
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island size&distance from mainland vs. species richness
- small island=increase in extinction
- close islands=increase in immigration
- large, close islands have an increase in amount of species
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Marine islands
- remote islands have fewer bird species
- near mainland has more species
- has no effect on ferns
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Why are there more species in the tropics than at higher altitudes?
there is more tropical area than polar area
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Habitat loss: frontier forests
- frontier forests=original forests
- leading cause of species extinction=habitat loss&exotic species
- species need undisturbed frontier forests to survive
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Biodiversity hotspots
- 25 hot spots
- 1.4% of the earth, houses 40-60% of species
- to qualify as a hotspot, an area must contain 1,500 or 300,000 endemic plant species in the world and must have lost at least 70% or more of their natural vegetation and habitat
- areas of concern because lots of diversity, these areas are in a developmental pressure
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Intraspecific competition among planthoppers
- planthoppers have a habit of aggregating, rapid growth, and the mobile nature of their food supply
- demonstrated intraspecific competition within populations of planthopper Prokelesisia marginata(probably result of limited resources)
- increased populations=lower survivorship, increased development time, and reduced body size
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Niches
- Hutchinson defined a niche as an n-dimensional hyper-volume(n equates the number of environmental factors important to survival and reproduction of a species)
- Are variables that define an environment
- Environmental factors that influence growth, survival, and reproduction of a species
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Overlap of niches
- Degree of competition depends on this
- Not much overlap=less competing
- Endimensional hypervolume=beyond 3D
- Niches are abiotic
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Fundamental niche vs. realized niche
- fundamental=physiological tolerance, ideal lab conditions, hypervolume, determined by physiological adaptions and parameters
- realized=ecological tolerance, real situation with competitors/predators, includes interactions such as competition that may restrict environments where a species may live(reality)
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Principle of competitive exclusion
- two species with identical niches cannot coexist indefinitely
- one will be a better competitor and thus have higher fitness and eventually exclude the other
- exception is a warbler=resource partitioning
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Flour beetle experiments
- Study of interspecific competition between T. confusum and T. castaneum under varied environmental conditions
- Growing two together suggested interspecific competition restricts the realized niches of both species to fewer environmental conditions
- When grown alone, both species thrived
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Feeding niches of galapagos finches
- Grant found differences in beak size among ground finches related to diet
- Size of seeds eaten can be estimated by measuring beak depths(individuals with deepest beaks fed on hardest seeds)
- After a drought, remaining seeds were very hard, so mortality was heavy in birds with smaller beaks
- Can separate niches by separating seed size
- Shows natural selection&intraspecific competition
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Competition and niches of small rodents
- If competition among rodents is mainly for food then small granivorous rodent populations would increase in response to removal of larger granivorous rodents(insectivorous rodents would show little or no response=noncompetitor)
- results supported this hypothesis, removed competition and numbers of small granivores increased
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Character displacement
- Because degree of competition is assumed to depend upon degree of niche overlap, interspecific competition has been predicted to lead to directional selection for a reduced niche overlap
- Directional selection=a mechanism to minimize interspecific competition
- Character of species shift in one direction to minimize competition and move niches further apart
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Exploitation
- Interaction between populations that enhances fitness of one individual while reducing fitness of the exploited individual(bad for individual being consumed)
- Predators kill and consume other organisms
- Parasites live on host tissue and reduce host fitness, but do not generally kill the host
- Parasitoid is an insect larva that consumes the host(same size as host)
- Pathogens induce disease
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Parasites that alter host behavior
- Rust fungus(Puccinia) manipulates growth of host mustard plants.
- Puccinia infects plant rosettes and invades actively dividing meristematic tissue
- Rosettes rapidly elongate and become topped by a cluster of bright yellow leaves
- Pseudo flowers are fungal structures including sugar containing spermatial fluids(attracts pollinators)
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Entangling exploitation with competition
- the presence/absence of a protozoan parasite(adeline) influences competition in flour beetles(tribolium)
- parasite lives as an intercellular parasite(reduces density of castaneum but has little effect on confusum)
- castaneum is usually the strongest competitor but with the presence of the parasite, confusum becomes the strongest competitor(exploitation alters competition and other factors-parasites reverse competitive ability of species)
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Exploitation and abundance
- Introduced cactus and herbivorous moth
- Prickly pear cactus was introduced to australia, which established populations in the wild
- Needed to control cactus, moth was found to be an effective predator(reduced 3 orders of magnitude in 2 years)
- Example of plastical/biological control
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Cycles of abundance in snowshoe hares and their predators
- snowshoe hares&lynx
- extensive trapping records
- proposal that abundance cycles are driven by variation in solar radiation
- another proposal suggested overpopulation theories(decimation by disease¶sitism, physiological stress at high density, starvation due to reduced food)
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population fluctuations
- predator-prey competition/oscillation
- lynx #'s increased when hare #'s decreased
- affected by predation, food, etc
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Role of food supply&predators on population
- Both in effect=dramatic change, centeragism
- Combined effect is greater than a single effect
- top down=predators
- bottom up=food
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predator prey oscillation model
- normal oscillation=predator&prey numbers vs. time
- but removing time off the x-axis and replacing it with prey reveals an elliptical oscillation
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Refuges
- to persist in the face of exploitation, hosts and prey need refuges
- in a simple environment, both prey and predators become extinct without refuges
- with a refuge, the prey populations survived but the predator population went extinct
- immigration/introduction of predators would cause regular oscillations
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Example of refuges
- prey mites and predator mites placed in a box with oranges and rubber balls with partial barriers to mite dispersal
- predator crawls while prey balloons
- provision of small wooden posts to serve as launching pads maintained population oscillations for 6 months
- shows habitat complexity and migration on its own
- they can maintain themselves
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Predator satiation by periodical cicadas
- periodical cicadas emerge as adults every 13-17 years
- large densities
- mass emergence of cicadas=predators overwhelmed
- cicada way to survive is to overwhelm
- predators kill a significant amount when cicada density is low
- as cicada density increases, predation is low
- as cicada numbers drop, the amount killed by predators increase
- predator-pey oscillation
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mutualism
- interactions between individuals of different species that benefit both partners
- facultative mutualism occurs when a species can live without its mutualistic parter(not dependent, but benefits)
- obligate mutualism occurs when a species is dependent on a mutualistic relationship(dependent for survival)
- there's evidence that eukaryotes originated as mutualistic associations
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Mycorrhizae and plant water balance
- Hardie suggested mycorrhizal fungi improve water relations by providing more extensive contact with moisture in rooting zone and providing extra area for water absorption
- fungus dissolve minerals, which mean better nutrients
- experiments show that plants with mycorrhizae maintained higher leaf water potential throughout a hot summer day
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Ants and bullshorn acacia
- Herbivores attempting to forage on acacia plants occupied by acacia ants are met by a large number of fast, agile, highly aggressive defenders
- Ant benefits: thorns provide living space, folliar nectaries provide sugar, beltian bodies are a source of oils and protein
- Example of obligate mutualism
- Performance of trees was better with ants, grew much faster w/ the removal of herbivores&competitors
- Survival of trees was greater&their were less herbivorous insects with the ants
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Coral mutualisms
- Zooxanthallae live within coral tissues
- Receives nutrients from coral, in return, coral receives organic compounds synthesized by zooxanthallae during photosynthesis
- Corals induce release of organic compounds with "signal compounds" that alter permeability of zooxanthallae cell membrane
- Corals control rate of zooxanthallae population growth and density by influencing organic matter secretion
- Zooxanthallae uptakes potassium and especially nitrogen(ammonium) excreted by the coral
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Snapping shrimp and coral
- Facultative mutualism
- shrimp chases away sea stars that try to attack coral
- predation is higher with out snapping shrimp
- coral is healthier with shrimp, increased fat body production.
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Animal-animal mutualisms
- cleaning behavior is an association in which various species of shrimp or small fishes clean larger fishes of ectoparasites
- facultative mutualism
- cleaner fish gets consumed to clean mouth of big fish
- cleaner fish gets a meal and big fish gets rid of parasites
- Blenny is nasty, imitates cleaner fish but rips out chunk of gill of big fish
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Honeyguide-human interaction
- natural human mutualism
- honeyguides are african birds which feed on beeswax and insects, guides mammals(including humans) to bees nests
- mammal robs nest for honey and honeyguide forages on bee larvae&wax
- honeyguide flies near mammal and makes a distinctive call
- bird flies away in a given direction then reappears, perches or flies again in the same direction, establishing a route, badgers produce whistles as they follow(native humans use similar whistles), bird behavior changes near site, search time is reduced to about 5 hours, nests would be inaccessible to birds without gatherer
- Honeyguides are brood parasites=lies eggs in another nest then those parents have to raise them, has sharp beaks to kill nest mates.
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Described species in the world
- -Land(insects) make up a majority of described species
- -Marine species are less studied and well known because most are deep sea organisms(pelagic)
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Global distributions of species
- trend of more species towards equator
- tropical rain forests and coral reefs have high species diversity(50-80% of all extant species)
- 1 hectare(2.4 acres) of rainforest can have 400 species of trees
- higher latitudes=less diversity
- pollinators are important in tropical rain forests(specific pollinators)
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community structure
includes attributes such as number of species, relative species abundance, and species diversity
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guild
- group of organisms that all make their living in the same fashion(all seed eating animals in the desert)
- not taxonomic, depends on lifestyle
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Species abundance
richness and relative distribution of their abundance
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lognormal distribution
- graphed abundance of species in collections as frequency distributions
- bell-shaped curves
- in most lognormal distributions, only a portion of bell-shaped curve is apparent(sample size has large effect&significant effort to capture rare species)
- three parts=rare, intermediate(most species), and common
- graphs show # of moth species vs. # of individuals in a species
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species diversity
- two factors define species diversity
- species richness(can be diversity also)=number of species in the community
- species evenness=relative abundance of species, doesn't equal species richness
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Species diversity
- a two tree community shows importance of abundance
- greater species evenness=greater species diversity
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Rank abundance curves
- can also portray relative abundance and species diversity within a community by plotting relative abundance of a species against their rank in abundance
- greater evenness=lower slope
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Environmental capacity
- in general, species diversity increases with environmental complexity or heterogeneity
- MacArthur found warbler diversity increased as vegetation stature increased(measured complexity as foliage height)
- habitat complexity positively contributes to species diversity
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Other aspects of biodiversity
- biodiversity=many different kinds of species, not species richness
- character diversity
- functional diversity
- community/ecosystem diversity
- genetic diversity
- population diversity
- family/order/phylum diversity
- species diversity
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character diversity
- different morphologies
- don't take into account taxonomy
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functional diversity
different tasks/jobs
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genetic diversity
amount of adapting alleles within group
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population diversity
different amounts of populations
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family/order/phylum
# of family, order, phylum
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species diversity
- richness&evenness
- alpha=diversity within habitat
- beta=measure of diversity within habitat
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niches&diversity of algae and plants
- hutchinson=phytoplankton are an exception to the competitive exclusion principle because they live in simple environments and compete for the same nutrients
- many species coexist without competitive exclusion
- environmental complexity may account for significant portion of the diversity
- other kinds of interactions(credation) can prevent competitive exclusion
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algal and plant species diversity and increased nutrient availability
- repeatedly observed negative relationship between nutrient availability and algal and plant species diversity
- adding nutrients to water or soils generally reduces diversity of plants and algae(reduces number of limiting nutrients)
- highest number of species are found in areas with lowest soil fertility
- number of ectomycorrhizal fungal taxa declined with amount of soil nitrogen content
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disturbance and diversity
disturbance is difficult to define as it involves departure from "average conditions"(average conditions may involve substantial variation)
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sousa's definition of disturbance
discrete, punctuated, killing, displacement, or damaging one or more individuals that directly or indirectly creates an opportunity for new individuals to be established.
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white&pickett's definition of disturbance
- any relatively discrete event in time that disrupts ecosystem, community, or population structure and changes resources, substrate availability, or the physical environment
- two major characteristics=frequency&intensity
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modes of competition
- resource
- interference
- intraspecific
- interspecific
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resource
- competition for a shared limiting resource
- anything in environment that's consumed
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interference
- direct aggressive interaction between individuals
- antagonist behavior towards individuals of another species
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intraspecific and interspecific
- intraspecific=competition with members of own species
- interspecific=competition between individuals of two species, reduces fitness of both
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competition
- both species compete for a limiting resource
- both species are harmed
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amensalism
- asymmetric competition for limiting resource
- one species is harmed, the other is not
- phytoplankton¯ophages, macrophages harmed in presence of phytoplankton
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predation¶sitism
- herbivory
- species eats another species
- one species benefits, while the other is harmed
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commensalism
- plant benefits from decomposers
- follicle mite=lives on our faces but doesn't affect us.
- one species benefits, while there's no effect on the other species
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mutualism
- zooxanthallae and coral
- fungus and algae in lichen
- seed dispersers
- symbiotic
- both benefits!!!
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intraspecific competition among herbaceous plants
- plant growth rates and weights increase as density decreases
- competition for resources is more intense at higher population densities
- usually leads to mortality among competing plants(self-thinning)
- weaker individuals=higher mortality
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