Module #6: Population Patterns Flashcards
Population Genetics
A group of interbreeding individuals
Population Ecology
A group of individuals of the same species inhabiting the same area
Difficulties in defining populations
- how do you determine inbreeding?
- with the definition of population ecology, there is no boundary given (spatially or otherwise)
- how does one define the “same area”, or its size?
Difficulties in defining populations
- how do you determine inbreeding?
- with the definition of population ecology, there is no boundary given (spatially or otherwise)
- how does one define the “same area”, or its size?
Exponential Population Growth Rate (Density independent growth) + factors affecting it
dN/dt = (b-d)N = rN
Factors affecting growth include stochastic environmental changes and disturbances
Exponential growth, solving for population at time t
Nt = N0e^rt
Doubling time
The time taken for a population to double its size, approximated by n = 0.7/r
Logistic Growth Rate equation (density dependent processes)
Dn/dt = rN(K-N/K)
*the closer N gets to K, the slower the rate of growth
*factors that affect logistic growth rates are parasitism, competition, predation
solving for population at time t, you get:
Nt = (N0K)/(N0+(K-N0)e-rt)
r-strategist species
They continually colonize temporary habitats, are opportunistic, have high growth rates, high fecundity, and short generation time, put little effort into raising young, so many will perish.
-Migration is a major component of their population dynamic
-“pioneer species” and poor competitors
-named after the intrinsic growth rate, r, in population growth equations
example: american oyster
K-strategist species
They live in stable environments, where the generation time is less than the habitat’s life span. They are often large, long-lived, very competitive, low birth/death rates and invest time and effort into raising young.
-they are likely to degrade habitat and overshoot the carrying capacity
examples: human, elephant
Extinction-and-colonization metapopulations (Levins, 1970)
A meta population consists of subpopulations characterized by frequent turnover, all subpopulations are equally susceptible to local extinction, and persistence of a species depends on there being enough subpopulations, unoccupied habitat patches, and dispersal to guarantee an equal rate of recolonization
*similar to IBT, but covers one species only
*patchy habitat may dictate existence as a metapopulation
*example: mountain sheep
Loose metapopulations
A set of populations of the same species, rates of mating, competition, and other interactions, are much higher within subpopulations than between them
*subpopulations are loosely linked/loosely interacting
Tight metapopulations
A set of conspecific subpopulations living in a mosaic of habitat patches, with a significant exchange of individuals between patches. Lots of interchange between subpops.
*Occurs where the distance b/n habitat patches is shorter than the species is physically capable of traveling, but longer than the distance most individuals travel in their life (can move b/n pops but usually don’t).
Source-sink (mainland island) metapopulations
Consists of a mixture of small populations prone to extinction and a large persistent population
Habitat
A region/area where a species or population usually lives. Characterized by a specific set of environmental conditions such as light availability, temp, moisture, etc.