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
In pred prey cycles, what does the term stable mean
Where a pair of populations
(predator, prey) which have a
return tendency to a particular
density
In pred prey cycles, what does the term cycle mean
Regular, identifiable pattern of population
sizes over time
What are the characteristics of a stable limit cycle
Both pred and prey go through predictable cycle
Predator lags behind prey
Population never reaches equilibrium
What are the characteristics of a stable point cycle
Both pred and prey populations settle at a fixed number
No or tiny oscillations of populations,
Can occur through dampened oscillation
When do unstable cycles occur
If it its a new cycle, sometimes the dynamics start this way then
become stable
Common when there is more than 1 ped or prey
What could happen if a predator is introduced to a new ecosystem
most introductions lead to their extinction
Can destabilise the ecosystem
Or over evolutionary time, c coexist and form stable limit or cycles
What are some limitations to predator prey cycles
Prey tend to have a refuge away from predators
Models assumes predation is random which it rarely is
Models assume similar generation time between predators and prey which is rarely true
Predators may be generalists and prey switching tends to stabilise populations.
Most cycles tend to be found in northern temperate regions, tropics are unknown
What is competition
Two or more species using the same limited resource to the detriment of both ie reciprocally negative interaction
2 types of competition
Consumptive competition
Interference competition
What are the types of consumptive competition
Scramble - occurs over a resource that is accessible to all competitors (that is, it is not monopolizable by an individual or group).
Exploitative
What interference competition
occurs directly between individuals via aggression
The greater the niche overlap, the greater the..
competition
What is the density dependent logistic growth model
dN over dt = rN(K-N over K)
What are the 3 outcomes of inter-specific competition
- Both species coexist
- Species 1 becomes extinct
- Species 2 becomes extinct
How can competiting species coexist
– Resource partitioning (species use resources
somewhat differently – temporal, spatial)
What is a fundamental niche
N-dimensional space where
species can survive & reproduce indefinitely,
includes environmental and behavioural conditions
What is character displacement
A rare phenomenon when species under selection to evolve niche dimensions with lower overlap. It leads to evolution of physical
characteristics among competitors that reflects more specialised role in
ecosystem
What is indirect competition
defined as conflict of one organism or species on another that is mediated or transmitted by a third. e.g predators both eating the same prey
In what areas can niche displacement take place
Character
Space
Niche
When may competitive ability evolve
evolve if the food web is
complex and no avoidance is possible
How can can predators control populations in a non lethal way
By creating a landscape of fear resulting in prey from reproducing as optimally as they avoid certain areas and spend more time being vigilant
What types of information can prey use to detect predators
Public - e.g acoustic/olfactory/visual cues
Private
What non lethal effects
Affects:
– population number
– behaviour
– distribution
What is private information
information which is known to the individual only (e.g., their own nesting history),
What is public information
Information available to everyone l (e.g., abundance of predators at a site)
What is the primary cause of songbird nest failure
Ricklefs 1969 said it to be predation
What is a win–stay, lose–switch strategy
The situation in which birds
continue to use similar nest-sites after nest success but
select different nest-site characteristics after failure
What is a stay–stay strategy
, choosing nest-sites irrespective of nest
fate
