Week 6 - 8 Flashcards
What 5 things can models be used for
Understanding population growth, equilibrium, limitation, regulation and persistence
What is the philosophy behind a model
it is an idealised form of a system
What two factors make a strong model
High in both biological understanding and empirical strength
Assumptions of logistic population growth
Carrying capacity is constant
Age structure does not affect growth
No genetic structure
Birth and death is linear to N
Carrying capacity has an instant effect– no time lags
Density crowding affects all individuals equally
Why does exponential growth not occur and what kind of models can be used instead
Other interactions curb growth such as disease, competition and predation so dynamic or multi-species models can be used
What shape is a density dependent growth
Population size has negative linear feedback– logistic growth
What is allee effect
When there is a positive population size or density and mean individual fitness
example of single species logistic growth
In Gause’s famous experiment, Paramecium caudatum, bursaria and aurelia all showed logistic growth; their density was dependent on the space and the food source
Potential example of exponential growth
Human population growth does not yet appear to be density dependent
Basic logistic growth models are flawed, what do they need to account for
Intra and inter generational interactions and age structure (turtles and sawtoothed grain beetles)
Time lags
Non-linear relationship between B&D and N (allee effects - guillemots)
Sex ratios and interactions with the environment (Gouldian finches)
Intra and inter sex interactions
Where can intraspecific interactions occur
Within generations (siblicide, more related to yourself) between generations (conflict between offspring wanting investment, and parent wanting more offspring) within sexes (male:male competition) between sexes (females being harassed)
What is the relationship between current fecundity and future survival
The less you invest in current fecundity, the more you can invest in future survival
What is population viability analysis
Set of analytical and modelling approaches
to assess the future course and risk of extinction in a population which can accommodate genetic demographic and environmental stochasticisty
Types of stochasticity that can influence populations
genetic demographic and environmental
What is a deterministic model
where the output of the model is fully determined by the parameter values and the initial conditions. e.g B,D,I, and E constant over time,
What is a stochastic model
models which possess some inherent randomness.
The same set of parameter values and initial
conditions will lead to an ensemble of different
outputs
What is demographic stochasticity
describes the randomness
that results from the inherently discrete nature of
individuals individuals. It has the largest largest impact on small populations.
What is environmental stochasticity
describes the randomness
resulting from any change that impacts an entire
p po ulation (such as changes in the environment). Its
impact does not diminish as populations become large.
How can genetic stochasticity lead to evolution
i) founder effects and genetic drift
ii) non-random assortment during reproduction
iii) inbreeding
What is a minimum viable population
Lowest population size for survival
– Space for stochasticity
– Space for genetic effects
•For a set period of time
What are the two overall reproductive strategies
r and K
What 2 parameters characterise a logistic growth curve
r and K
3 Ways in which individual species models can be applied
Pest management
– Conservation management & reintroductions
– Harvesting (Brown bears)
4 types of predator and prey cyle
Stable limit cycles
Stable point cycles
Unstable cycles
Extinction
