Lec 20: Population Ecology
- Population: group of individuals of 1 species living in a given area
- Use common resources, cope with similar environmental factors, interact with each other
1. Population characteristics?
- Dispersion: pattern of spacing b/w individuals
- Density: # of individuals per unit area
- Age structure: # of individuals of different ages
- Sex ratio: ratio of males to females
- Range: geographic area a population resides in
- Population size: # of individuals
2. Dispersion patterns?
- Clumped: individuals in patches (ex. Shared resource, social interaction, predator avoidance)
- Uniform/regular: individuals evenly spaced (territoriality, competition for scarce resource)
- Random: unpredictable spacing of individuals (biotic, abiotic conditions are homogenous)
3. Quadrat sampling (sessile or slow moving)?
- N = qAp/Aq
4. Mark recapture (mobile animas)?
- N = m1n2/m2
5. Survivorship curves? Types and x-axis, y-axis.
- Y-axis: number of survivors (Nx), X-axis: age (years)
- Or y-axis: number of survivors (log scale), X-axis: % of max life span.
- Type 1: mortality increases w/ age (humans)
- 2: Constant over time (squirrels)
- 3: mortality decreases w/ age (oysters)
6. Strategy A vs B?
- Breed young
- Breed often
- Many small babies
- Small body size
- Die young
- Little parental care
- Breed late
- Breed rarely
- Few large babies
- Large body size
- Die old
- Long parental care
7. Principle of allocation: individuals divide a finite amount of resources among multiple needs:
- Today: growth, maintenance, reproduction
- Whole life: present, future
8. Rate of change in pop. size:
- r = rate of increase per capita
- When b is high, d is very low, r is at rmax (intrinsic rate of growth)
- Exponential growth: dN/dt = rmax*N (ie. unlimited resources)
- Logistic growth: dN/dt = rmaxN*(K-N)/K [(K-N)/K = proportion of carrying capacity still available for growth]