EE27 Flashcards
What is an important component when recognising whether a scenario is density dependent?
Density dependence is per capita (individual rate)
if it concerns whole population it is not density dependent
Density dependent or not?
- big populations grown faster as more reproductive individuals
- average number of offspring per individual is often smaller in higher density population
- More deer died in location A
- A larger % of deer died in location A
- As population size increases the number of deaths per capita decreases
- not density dependent
- density dependence as indicates depence of a per capita rate.
- not density dependent
- density dependent
- density dependent
What is the per capita growth rate?
dN/dt/N
What is the density dependent model of growth?
makes dN/dt/N decrease with N instead of staying constant. therefore dN/dt/N=r(1-N/K) K= carrying capacity When N is small dN/dt/N=r when N=K dN/dt/N=0 decreases as N increases.
What is the logistic growth curve of Time against population size?
sigmoidal curve,
population size changes with time
assumes smooth linear reduction in per capita pop growth rate with density
sigmoidal curve happens eg. in yeast if waste not removed and nutrients not added.
* neither contest or scramble is assumed in logisitc model of smooth decline as it assumes linear increase in mortality/ linear decrease in per capita growth rate
What are the types of competition?
resource exploitation and interferance
What is more likley to lead to a population persistence scamble or contest?
contest as in scramble at high population, all dont get enough, whereas in contest atleast someone individuals will always remains`
What is the allele effect?
correlation between population size and density and mean individual fittness. - often measured per capita poplulation growth rate.
What is the equation for the logistic model, what does it add?
dN/dt=r(1-N/k)N
adds in intraspecific competition
What is compensation?
degree to which larger numbers are compensated for by higher mortality and lower fecundity
When does overcompensation occur?
when survivorship, growth or fertility are more and more suppressed by crowding and depletion of resources that ultimately there are no more resources to support any more individuals = all die/no more are made.
What does the undercompensating process allow?
number of survivors to increase as starting population is decreased.
What is exact compensation?
number of survivors will be constant or process itself will compensate
Give examples where increasing density does not decrease per capita growth rate or increase per capita mortality?
whales, low density = low birth rate
predator swamping in wildebeast.
pathogen invasion - threshhold for infection success
What kind of compensation does scramble competition lead to?
extreme over compensation
increase in number is not matched by decrease in growth rate until all resources are used
What kind of compensation does contest competition lead to?
exact compensation
as numbers increase, growth rate decreases as there is an exact number of places available.
Give an example of where positive density dependence can be seen?
guilimots, as breeding success increases with number.
