Define
Population state
Snapshot of the number of individuals and their spread, at a given point in time
Define
Population dynamics
Biotic and abiotic factors that cause population states to change with time
Describe
What members of a population do
- Rely on same resources
- Influenced by similar environmental factors
- Likely to interact and breed
Although ecologists are less concerned about whether pop. members breed
Define
Population abundance
Number of individuals in the population
Define
Population density
- Number of individuals per unit area (how individuals are spread out in space)
- Not a static property
Define
Biomass density
Total weight of organisms in an area
Describe
The consequences of low population density
- More resources for each individual
- Individuals less likely to encounter one another (spread disease, fight, mate)
What are the two types of competition?
- Interference competition: overt, like two bears fighting
- Exploitation competition: covert, like two bears trying to eat all the berries in a bush
Describe
Mark-recapture
- Capture individuals, mark them, release them
- Capture 2nd set of individuals, determine how many have been marked already
- Calculate N, from M/N = R/C
What are the three types of population dispersion?
Clumped, uniform, random
Describe the causes of
A clumped dispersion
- Babies tend to stay near their parents
- Localized suitable environmental conditions
- When animals travel in groups
Describe the causes of
A uniform dispersion
- Results from direct interactions between individuals (territoriality)
- Death of individuals when competitors are too close
- When individuals move from one another (ex: territorial wolf-packs)
Describe the causes of
A random dispersion
- Individuals arriving at locations randomly when there are no spatial interactions or when there are multiple different spacial interaction functions
What is the formula for changes in population size (for a short period of time)?
ΔN/Δt = B(t) - D(t) + I(t) - E(t)
ΔN: change in population density
What are the two factors determining change in population size, in populatons not experiencing large amounts of immi/emigration?
Reproductive state and survivorship curves
What are the links between carrying capacity and growth rate?
- Over carrying capacity: positive growth rate
- Under carrying capacity: negative growth rate
- At carrying capacity: neutral growth rate
What is Type I survivorship curve?
- Low death rate when young
- High death rate when old
- Happens in large species
Shape: –\
What is Type II survivorship curve?
- Constant death rate
- Happens when large percentage of mortality comes from predation
Shape: \
What is Type III survivorship curve?
- High death rates when young
- Low death rates when old
- Seen in organisms that produce large amount of offspring but offer little care
Shape: __/
