Midterm 1 Flashcards
(39 cards)
What is ecology?
The study of living organisms’ interactions with EACH OTHER and their ENVIRONMENT
What is population ecology?
The study of the factors controlling
- population size,
- age structure,
- density
- and distribution.
What is the law of parsimony?
The simpler solutions are more likely to be correct than the complex ones (problem-solving principle)
What is a population?
A group of organisms of the SAME SPECIES LIVING and REPRODUCING together.
What are the assumptions of exponential growth model?
- No I or E
- No age structure
- No genetic structure
- Continuous growth (no time lags)
- b and d are constant (unlimited resources)
What is a discret exponential population growth?
It’s a population that grows not continuously over time with non-overlapping generations.
What are the differences between r and lambda?
r : units
lambda : no unit, specific from t to t+1
What implies a model of stochastic variation?
When r varies.
In a model of environmental stochasticity, when do you know there will be an extinction?
When variance (pie2r) is > 2r. 𝝈𝟐𝒓 >𝟐r
Name some factors that explain why exponential growth decreased in density-dependant models.
- Space limitations
- Food limitations
- Accumulations of waste products
- Competitors
- Predators
- Disease, parasites
What is K?
K is the carrying capacity: the maximum population size that can be supported under limited resources
When to use the logistic model?
When there is limited resources
What are the assumptions of the logistic growth model?
- No I or E
- No age structure
- No genetic structure
- Continuous growth (no time lags) (like in exponential growth)
- CARRYING CAPACITY IS CONSTANT
- LINEAR DENSITY-DEPENDENCE (per capita population growth rate) IS LINEAR
*biggest difference with exponential model: b d are not unlimited
What is a time lag in pop ecology?
Delay in population response to factors affecting population growth.
When is the population growth rate is maximal in a logistic growth model?
Under limited resources (logistic growth model), population growth rate is maximal when N = K/2
What is a time lag?
A time lag is a delayed density-dependence (as density-dependent growth is effectively a negative feedback of N on dN\dt)
In a logistic population with a time lag, explain the population trajectoire.
- rtau small : logistic growth
- rtau moyen: not constant oscillations
- rtau grand: stable cycles
For time lag, what is amplitude and what is period?
Amplitude: increases with increasing rtau
Period: 4tau
When does rd exhibits chaos?
When rd > 2.570
Explain why the period is always about 4τ.
The distance from K to the amplitude is about one quarter of the cycle. The distance is equal to tau, because it’s the amount of time need so the system response to the carrying capacity. If tau is about ¼ of a cycle, then a full cycle is about 4*tau.
What are the assumptions of the age-structured exponential growth model?
- Closed population (no E or I)
- No genetic structure
- No time lags
- B and D constant FOR EACH AGE CLASS
- Stable age distribution
What is r and k selection?
r selection: lof of offspring, low survivor (small bodied)
k selection: not a lof of offspring, high survivorship
What is b(x)?
b(x) = fecundity schedule: the average number of females offspring by females of a particular age
What is S(x)?
S(x) = cohort survival: the number of individuals of a cohort that survive from birth to age x
