Lecture 18: Age Structured Populations Flashcards
Fecundity and survivorship depend on
age
Key components of life history strategy
lifespan, timing of reproduction, number of offspring, and parental investment in offspring
Without age structure, N=24 individuals…
is imagined as 24 equal individuals whereas really the population is broken down into ages classes (each with distinct reproductive and survivorship capabilities)
Life tables
summarize life events that are statistically expected for average individual of specified age (usually only consider females)
Age-class intervals
arbitrary units of time (for humans 5 years)
Survivorship curve
graph of Ix vs. x
- shape of this curve is characteristic of a species
If mortality is constant with age
you get exponential decline (type II)
Pleiotropy
one gene may have multiple functions (ex. P53 suppresses tumours in youth but later kills stem cells)
Antagonistic pleiotropy
Theory by G. C. Williams. One gene might help you when you’re young but be detrimental when you are older (wouldn’t be selected against because ti does not affect the fitness of the carrier)
monocarpic
produces fruit once thus semelparous
monocarpic perennial
Has more than two seasons of growth before flowering
Scarlet Gilia
flexible semelparity based on resources (will shift to iteroparous when there are fewer pollinators)
K strategy
- slower growth
- longer gen. times
- larger body size
- more investment in somatic growth
- better competitors
- poor at dispersal
- more investment in individual offspring
- iteroparity more likely
- shade tolerant (plants)
r strategy
- faster growth
- shorter generation time
- smaller body size
- more investment in gonad
- poor competitors
- produce more but lighter seeds
- semelparity more likely
- shade intolerant, seed dormancy
- born to run
semelparity selects for
synchrony
Selection usually favours reproduction at…
an earlier age (more gene copies into population), but can be countered by a need to accumulate resources
What does Vx affect?
- success of captive breeding/release programs for conservation (should only release animals with highest reproductive value)
- roaming behaviour should coincide with age of high Vx
- age of Vx affects attractiveness to potential mates
Fecundity schedules
- Mx = number of daughters born to a female of age x during the interval x to x+1
- shape of m curve characteristic of a species
- reproductive period usually preceded by resource-accumulation
Fecundity-survivorship trade-offs
cost of reproduction
