Unit 2 Ecology Review

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170 Terms

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metapopulation
a set of spatially isolated populations linked by dispersal of individuals or gametes
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metapopulations are characterized by repeated \_______ and \_______ of the small individual populations
extinctions, colonizations
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source
the number of individuals that disperse to other populations is greater than the number of migrants they receive (place where population is doing well)
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emigration \> migration

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sink
receive more migrants than the number of individuals that disperse to other populations (where organism goes to die pretty much)
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migration \> migration

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metapopulation dynamics (high migration)
causes the metapopulation to behave as a single, large population
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metapopulation dynamics (intermediate migration)
colonization of patches left open by subpopulation extinction, mosaic of occupied and unoccupied patches
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metapopulation dynamics (no migration)
each subpopulation becomes isolated and at risk of extinction
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dp/dt \= cp(1-p) - ep
extinction and colonization of patches
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p \= proportion of habitat patches occupied at time t

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c \= patch colonization rate

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e \= patch extinction rate

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c \> e for metapopulation to persist

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isolation by distance
when patches are too far apart
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effect of patch size
small patches may be hard to find and have high extinction rates
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rescue effect
High rates of immigration that protect a population from extinction
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extinction can be caused by what two reasons for metapopulations?
1. Patchiness in habitat makes dispersal from other populations difficult
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2. Environmental conditions changing rapidly + in unpredictable manner

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T/F All populations form metapopulations
False
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What happens if e/c \> 1 what will happen in metapopulation?
metapopulation will go extinct
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Habitat Fragmentation example
Spotted owls became Northern spotted owl, Mexican spotted owl, and California spotted owl because of isolated patches
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Isolation by distance + effect of patch size example
Skipper butterflies- cows stopped grazing leading to loss of grass land leading to smaller + isolated patches making them less likely to be colonized by more butterflies to persist
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effect of patch size example (unaffected by isolation)
Shrews- live on islands in lakes, island occupancy is strongly affected by island size, but unaffected by isolation because they are such strong swimmers
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habitat fragmentation
Breakup of a habitat into smaller pieces, usually as a result of human activities, turns populations into metapopulations and into isolated populations no longer linked by dispersal
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life history characteristics
-age and size at sexual maturity
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-amount and timing of reproduction

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-survival and mortality rates

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overall pattern of life history:
growth, reproduction survival
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What do differences in life history come from?
genetic and environmental variation
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optimal life histories maximize \_________
fitness
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fitness
Ability of an organism to survive and reproduce in its environment
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metamorphosis
abrupt transition in form between larval and juvenile stages
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-different body forms, habitats, and food

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ex: caterpillar to butterfly, tadpole to frog

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phenotypic plasticity
our genotype produces different phenotypes under different environmental conditions
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phenotypic plasticity example
trees in the desert grow shorter and with smaller leaves than in cool, moist climates
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Polymorphism
The existence of more than one form of a genetic trait.
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example of morphs
tadpoles
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omnivore morph- grow slowly, metamorphose later w/ higher chance of survival, permanent ponds

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carnivore morph- grow faster, metamorphosize earlier, temporary ponds

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asexual reproduction
cell division (binary fission) done by all prokaryotes and most protists
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sexual reproduction
most plants, animals and many fungi + protists
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3 disadvantages of sexual reproduction
-an individual transmits only half of its genome to the next generation
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-population growth rate is only half that of asexually reproducing species

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-recombination and chromosome assortment during meiosis can break up favorable gene combinations

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advantage of sexual reproduction
recombination promotes genetic variation and increased ability of populations to respond to environmental challenges
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the cost of males meaning
asexual reproduction produces twice as many offspring as sex
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semelparous
species that reproduce only once
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iteroparous
species can reproduce multiple times
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r
intrinsic rate of increase of a population
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K
carrying capacity of a population
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r-selection
selection for high population growth rates; an advantage in newly disturbed habitats and uncrowded condition
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-short life spans

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-rapid development

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-early maturation

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-low parental investment

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-high reproductive rates

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K-selection
selection for lower growth rates in populations that are at or near K; an advantage in crowded conditions; efficient reproduction is favored
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-long life spans

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-develop slowly

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-late maturation

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-high parental investment

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-low reproductive rates

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gradient between r and K species
oysters \---\> frogs \---\> gorillas
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life history trade-offs
large investment in offspring but few offspring
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lots of offspring but little parental investment and lower survival

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large offspring but few offspring

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small offspring but many offspring

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if there is a trade-off between reproduction and growth rate, then:
the more offspring you produce, the shorter your lifespan
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trade-off between reproduction and survival
higher fecundity \= lower survival
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population abundance
number of individuals
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population density
Number of individuals per unit area
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on a 20-hectare island, there 2500 lizards. What is the population density?
125 hectare^-1
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isolated patches can be linked by \________
dispersal / gene flow
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clones are formed by
budding, apomixis (unfertilized eggs), horizontal spread (likes trees, offspring produced as organism grows)
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abiotic factors that limit distribution
water, temperature, pH, sunlight, nutrients, etc.
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biotic factors that limit distribution
predation, parasitism, competition, disease
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dispersal limitation
A situation in which a species' limited capacity for dispersal prevents it from reaching other areas
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population
group of individuals of the same species that live in the same area
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geographic range
the entire geographic area over which a species is found including all of its life stages (migration)
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Nearly Regular Distribution
due to competition for resources
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Random distribution
due to short dispersal distances or targeted resource availability
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Clumped distribution
due to short dispersal distances or targeted resource availability
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-ex: trees clumped around water source

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absolute population size
the actual number of individuals in a population
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relative population size
number of individuals in one time period or place relative to the number in another
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area-based counts
individuals in a given area or volume are counted and averaged to estimate population size
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-usually quadrats

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-for immobile organisms (ex: coral)

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40, 10, 70, 80, and 50 cinch bugs are counted in five 10 cm x 10 cm (0.01 m2) quadrats. What is the population density per m^2?
5000 m^2
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(40 + 10 + 70 + 80 + 50) / 5 \= 50 / 0.01 m^2 \= 5000 m^-2

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distance methods
distances of individuals from a line or point are converted into estimates of abundance
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-used for large area

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line transects
Observer travels along line and counts individuals and their distance from the line
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mark-recapture studies
A subset of individuals is captured and marked or tagged, then released.
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At a later date, individuals are captured again, and the ratio of marked to unmarked individuals is used to estimate population size.

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-used for mobile organisms (ex: fish)

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-more organisms recaptured is an indicator of small population size