2nd Half - Exam Review Flashcards
Intrinsic Growth Rate
The max rate at which a population can grow under ideal conditions
- r in exponential
- Lambda geometric model
What purpose do the mathematical models serve?
- Simplify complexity
- Make (quantitative) predictions
- Explore various scenarios
- Test hypothesis and mechanisms
- Communicate between disciplines
- To criticize models and decide if assumptions are realistic
Geometric Growth
Populations grow geometrically when reproduction occurs at regular time intervals
Population Increases
- By a fixed proportion - lambda
- Constant ratio of change from one time to the next
- Over discrete, non overlapping time intervals
- The larger the population becomes, the faster it grows
- Used to model populations with discrete breeding seasons or generations.
Exponential Growth
Populations grow exponentially when reproduction occurs continuously
- at a rate proportional to its current size
- continuously
- Larger the population becomes the faster it grows
- Used to model populations that grow continuously (rather than discrete intervals)
What is the critical value for lambda?
1
What is the critical value for r?
0
What does the critical value for intrinsic growth rate mean?
No growth or change in population size
What is the differences + similarities between exponential and geometric growth? (2 and 2)
Similarities:
1. Both show rapid growth due to multiplication
2. Both involve some intrinsic rate of increase
Differences
1. Geometric growth is discrete, exponential growth is continuous
2. Different interpretation of growth rates
Liebig’s law of the minimum
The rate of biological process is limited by the factor in least amount relative to the organism’s requirements
- some factor is limiting
What are the 2 main types of limits?
1.Density dependant factors - become more important as the population size increases
- lead to carrying capacity
- often due to increased infraspecific competition at higher population
- Density independent factor - affect the population size regardless of its density
Carrying capacity
The max number of individuals of a species that can be supported by the available resources in a particular environment
What factors become more important as the population size increases (3)
- decrease in birth rate
- increase in death rate
- both
When is negative density dependance observed?
- When the relationship between r max and density is -ve
- Due to intraspecific competition
Overshoot
If population exceeds carrying capacity
- decrease in birth rates
- increase in death rate
- both
Leads die off
Positive density dependent (allee effect)
The growth rate or survival of population increases as the population density increase
Due to:
- finding mate
- cooperative behaviours
- predator satiation
- resource availallity (niche construction)
Logistic Equation Model
The common model for negative density dependence
- S-shaped
- Inflection point
- Exponential phase before inflection point
- Logistic phase after inflection
K = carrying capacoty
BIDE Model of Population Dynamics
- Births
- Immigration - individuals moving into the population
- Deaths
- Emigration - The movement of individuals out of the population to other areas
What are the 3 types of fluctuation within a population
- Regular - tied to seasonal changes in environment
- Irregular - not tied to seasonal changes
- Cyclical - Intrinsic factors, result in a regularish pattern in the species, species interactions
Monotonic Damping
A smooth approach to carrying capacity
Damped Oscillations
Regular fluctuations that that decrease overtime
Stable limit cycle
Regular fluctuations that is consistent over time
Chaos
Complex, unpredictable and irregular fluctuations
Density Independent Factors: Due to stochasticity
Due to stochasticity (conditions are changing in complex ways), typically unpredictable events
- Disease outbreaks (biotic), new disease not present (disease can be density dependant)
- Natural disasters (abiotic)
- Human disturbances
A population that is more variable is less stable: (4)
- Stability - The maintenance of a relatively constant population size over time within a given geographic area (in terms of population).
- Fluctuations can lead to periods of low population size
- Small populations are more vulnerable to environmental changes and stochastic events
- Small populations are thus at much greater risk of extinction than large populations