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CanuckGirl
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what does population ecology describe?
describes population density, dispersion, and demography
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define density. what does it usually require?
- number/ unit area (or volume)
- usually requires sampling
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what are some example of sampling? (3)
- sample plots (ex. quadrants)
- indirect indicators (counting nests, droppings)
- for animals mark and recapture
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what is the equation for the mark and recapture method?
N= (# marked)(total # caught second time)/ (# of marked 2nd time)
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what are some problems with the mark and recapture method? (3)
- migration of animals
- animals being preyed because of tag or labelling
- animals avoid traps more/ go into traps more for free food
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define dispersion.
pattern of spacing
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list the 3 types of dispersion.
- clumped
- uniform
- random (rarely seen)
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what is an example of clumped dispersion and what does it facilitate?
- food, nesting sites maybe clumped
- may facilitate mating, social behaviour
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what does uniform dispersion indicate? what is an example?
- indicates antagonistic interactions
- ex. territoriality; plant allelochemicals (inhibit growth of other plants)
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what does random dispersions indicate?
- indicates no interactions
- ex. some trees and ferns
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define demography.
study of vital statistics that affect population size
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what are some vital statistics? (2)
- birth and immigration rates=increase population
- death and emigration= decrease population
- (can vary for gender and diff age classes)
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what is a life table? what does is measure?
- summarizes vital statistics of a population by following a cohort from birth to death
- measures mortality, survivorship, births etc.
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what are survivorship curves?
plot proportion of cohort still alive vs. age
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what is type 1 species? (3)
- have small # of well-cared offspring
- many survive to old age
- greatest mortality later in life (old age)
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what is type 3 species? (3)
- have many offspring with no parental care
- few survive for long until old age
- greatest mortality early in life
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what is type 2 species? (2)
- intermediate between type 1 and type 3
- roughly constant mortality rate experienced regardless of age
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Natural selection should favour strategies that maximize ______________________________.
lifetime reproductive success (fitness)
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lifetime reproductive success is affect by what 3 things? what does all of these features involve?
- clutch size
- # of reproductions/ lifetime
- age at first reproduction
- all involves trade-offs (limited energy budget)
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what is clutch size? what is the correlation between clutch size and offspring?
- = # of offspring/ event
- smaller clutch <----> bigger offspring
- bigger clutch <----> smaller offspring
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how does age at first reproduction relate to lifetime reproductive success?
- early breeding females may be smaller which lead to:
- produce smaller clutches
- less energy for later clutches
- leads to lower lifetime reproductive success
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Population growth can be modelled __________________.
mathematically
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what is the exponential growth model?
- assumes maximum rate of growth (rmax)
- (maximum birth rate; minimum deaths)
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what is rmax?
maximum rate of growth
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what is the downside of exponential growth model?
such growth (rmax) cant be maintained forever
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what is the logistic population growth model?
population limited by carrying capacity (K) of the environment
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Life histories can be related to the _____________.
logistic model
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define "r-selected" species?
evolved to maximize rmax
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what are some characteristics of "r-selected" species? (6)
- population size can increase quickly
- favours opportunists
- many small offspring
- no parental care
- mature rapidly
- type 3 survivorship curves (most die young)
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define "k-selected" species.
evolved in populations that were near carrying capacity (high densities)
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what are some characteristics of "k-selected" species? (4) what is an example?
- few big offspring
- parental care
- many have long life
- type 1 survivorship curves
- ex. elephants and humans
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what 2 things regulate population size?
combination of density dependent and independent factors
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In density dependent population regulation, effects increase as population size __________.
increases
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how would less resources/individuals affect population?
less resources--> less food, territories, nest sites--> lower survival, less offspring
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what density dependent factors will tend to keep populations near K? (3)
- less resources
- predation increases
- crowding
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As a density dependent factor, how does crowding change behaviour or physiology?
delayed maturity, lower offspring
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what are the 2 density independent factors?
- abiotic factors (weather, disasters)
- know back population size , no matter how big population
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Some species show regular population cycles. "regular" cycles maybe due to?
- due to time lags of density-dependent factors (ex. predation, epidemics and intrinsic changes)
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why has the human population increased so? (5)
- antibiotics and vaccines
- agriculture
- technology
- clean water
- sanitation
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growth rate not the same in all countries. what is it influenced by?
- growth rates influenced by age structure
- lots of kids now= increasing population later
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what is the fertility rate in Canada?
1.6
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so what is the carrying capacity for us? what is he good news in this?
- estimates average 10-15 billion
- good news= growth is slowing
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what is an ecological footprint?
land and water area needed by a nation or person to get all of its resources and dispose of its wastes.
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are resources evenly distributed in the world?
resources are limited and not evenly distributed
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human population increase is decreasing ___________________.
carrying capacity for other species
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