Chapter 13 - Population Dynamics over Space and Time Flashcards
All populations experience fluctuations over time. Give some reasons for these fluctuations.
Availability of food and nesting sites, predation, competition, disease, parasites, weather or climate.
How does body size affect population survival?
Smaller animals reproduce quicker; respond faster to ideal conditions.
Smaller animals have higher SA:V; more affected by negative conditions.
Larger animals maintain homeostasis, more resilient to changed environment.
What does unusually high or low numbers of an age group suggest about a population?
The population experienced unusually high birth or death rates in the past.
What is overshooting?
When a population grows beyond its carrying capacity.
What is a die-off?
A substantial decline in density that typically goes well beyond the carrying capacity.
When can an overshoot occur?
When carrying capacity declines from one year to the next.
What are population cycles?
Regular oscillation of a population over a longer period of time.
What is delayed density dependence?
When density dependence occurs based on a population density at some point in the past.
What causes delayed density depedence?
Delay between environmental conditions changing and reproduction.
How is the logistic growth model modified for delayed density dependence?
N is now at tau time units in the past.
What are damped oscillations?
A pattern of population growth in which the population initially oscillates but the magnitude of the oscillations declines over time.
What does the delayed density dependence intrinsic growth equation tell us?
Population slows its growth when the population’s size at tau time units in the past approaches the carrying capacity.
What happens as time delays increase? What does this mean for the population?
Density dependence is further delayed and the population is more prone to both overshooting and undershooting the carrying capacity.
What does a high r value mean in the delayed density dependence intrinsic growth equation?
Can make an overshoot of carrying capacity more likely.
What does the amount of cycling in a population experiencing delayed density dependence depend on?
The product of r and tau.
What values of rtau indicate damped oscillations in a population?
0.37 <rtau>1.57</rtau>
For what value of rtau does no oscillations occur?
rtau<0.37
What is a stable limit cycle?
A pattern of population growth in which the population continues to exhibit large oscillations over time.
For what values of rtau does a stable limit cycle occur?
> 1.57
What is this graph displaying?
A population approaching the carrying capacity with no oscillations.
What is displayed in this graph?
Damped oscillations
What is this graph depicting?
Stable limit cycle.
What are some possible explanations for delayed density dependence?
- Organisms cans store nutrient and energy reserves
- Time delay in development from one life stage to another
Are small or large populations more vulnerable to extinction?
Small
What is a deterministic model of populations?
A model that is designed to pick a result without accounting for random variation in population growth rate?
What is a stochastic model of populations?
A model that incorporates random variation in population growth rate.
What makes stochastic models necessary for modelling populations?
Not every individual within a population has the same birth rate or the same probability of dying.
What is demographic stocasticity?
Variation in birth rates and death rates due to random differences among individuals.
What is environmental stocasticity?
Variation in birth rates and death rates due to random changes in environmental conditions.
What are some examples of environmental stoacsticity?
Changes in weather, natural disasters.
When is a population more likely to go extinct?
When it randomly experiences years of low birth rates or high death rates.
When do metapopulations occur?
When a habitat is fragmented. Can be natural or caused by human disturbance.
What is habitat fragmentation?
The process of breaking up a large habitat into smaller habitats.
What is this equation? Define each variable.
Basic model of metapopulation dynamics.
p - Proportion of occupied patches when colonization and extinction in metapopulation reach equilibrium.
e - fixed probability of each patch becoming unoccupied
c - fixed probability that each unoccupied patch could become colonized
What does the basic model of metapopulation dynamics indicate? How can this be achieved?
Increasing number of occupied patches increases the total number of individuals in the meta population assuming each patch has equal numbers. Achieve this by increasing colonization (corridors) or decreasing extinction (reducing major causes).
Are small or large patches more likely to be occupied? Why?
Large; small patches support lower numbers and likely to experience higher rates of extinction.
What makes an unoccupied patch more likely to be colonized>
Located close to an occupied patch.
What is the rescue effect?
When dispersers supplement a declining subpopulation and thereby prevent the subpopulation from going extinct.
