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what does population ecology describe?
describes population density, dispersion, and demography
define density. what does it usually require?
- number/ unit area (or volume)
- usually requires sampling
what are some example of sampling? (3)
- sample plots (ex. quadrants)
- indirect indicators (counting nests, droppings)
- for animals mark and recapture
what is the equation for the mark and recapture method?
N= (# marked)(total # caught second time)/ (# of marked 2nd time)
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
pattern of spacing
list the 3 types of dispersion.
- random (rarely seen)
what is an example of clumped dispersion and what does it facilitate?
- food, nesting sites maybe clumped
- may facilitate mating, social behaviour
what does uniform dispersion indicate? what is an example?
- indicates antagonistic interactions
- ex. territoriality; plant allelochemicals (inhibit growth of other plants)
what does random dispersions indicate?
- indicates no interactions
- ex. some trees and ferns
study of vital statistics that affect population size
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)
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.
what are survivorship curves?
plot proportion of cohort still alive vs. age
what is type 1 species? (3)
- have small # of well-cared offspring
- many survive to old age
- greatest mortality later in life (old age)
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
what is type 2 species? (2)
- intermediate between type 1 and type 3
- roughly constant mortality rate experienced regardless of age
Natural selection should favour strategies that maximize ______________________________.
lifetime reproductive success (fitness)
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)
what is clutch size? what is the correlation between clutch size and offspring?
- = # of offspring/ event
- smaller clutch <----> bigger offspring
- bigger clutch <----> smaller offspring
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
Population growth can be modelled __________________.
what is the exponential growth model?
- assumes maximum rate of growth (rmax)
- (maximum birth rate; minimum deaths)
what is rmax?
maximum rate of growth
what is the downside of exponential growth model?
such growth (rmax) cant be maintained forever
what is the logistic population growth model?
population limited by carrying capacity (K) of the environment
Life histories can be related to the _____________.
define "r-selected" species?
evolved to maximize rmax
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)
define "k-selected" species.
evolved in populations that were near carrying capacity (high densities)
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
what 2 things regulate population size?
combination of density dependent and independent factors
In density dependent population regulation, effects increase as population size __________.
how would less resources/individuals affect population?
less resources--> less food, territories, nest sites--> lower survival, less offspring
what density dependent factors will tend to keep populations near K? (3)
- less resources
- predation increases
As a density dependent factor, how does crowding change behaviour or physiology?
delayed maturity, lower offspring
what are the 2 density independent factors?
- abiotic factors (weather, disasters)
- know back population size , no matter how big population
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)
why has the human population increased so? (5)
- antibiotics and vaccines
- clean water
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
what is the fertility rate in Canada?
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
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.
are resources evenly distributed in the world?
resources are limited and not evenly distributed
human population increase is decreasing ___________________.
carrying capacity for other species