Lecture 18: Age Structured Populations

Question 1

Fecundity and survivorship depend on

Answer 1

age

Question 2

Key components of life history strategy

Answer 2

lifespan, timing of reproduction, number of offspring, and parental investment in offspring

Question 3

Without age structure, N=24 individuals…

Answer 3

is imagined as 24 equal individuals whereas really the population is broken down into ages classes (each with distinct reproductive and survivorship capabilities)

Question 4

Life tables

Answer 4

summarize life events that are statistically expected for average individual of specified age (usually only consider females)

Question 5

Age-class intervals

Answer 5

arbitrary units of time (for humans 5 years)

Question 6

Survivorship curve

Answer 6

graph of Ix vs. x

- shape of this curve is characteristic of a species

Question 7

If mortality is constant with age

Answer 7

you get exponential decline (type II)

Question 8

Pleiotropy

Answer 8

one gene may have multiple functions (ex. P53 suppresses tumours in youth but later kills stem cells)

Question 9

Antagonistic pleiotropy

Answer 9

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)

Question 10

monocarpic

Answer 10

produces fruit once thus semelparous

Question 11

monocarpic perennial

Answer 11

Has more than two seasons of growth before flowering

Question 12

Scarlet Gilia

Answer 12

flexible semelparity based on resources (will shift to iteroparous when there are fewer pollinators)

Question 13

K strategy

Answer 13

• 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)

Question 14

r strategy

Answer 14

• 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

Question 15

semelparity selects for

Answer 15

synchrony

Question 16

Selection usually favours reproduction at…

Answer 16

an earlier age (more gene copies into population), but can be countered by a need to accumulate resources

Question 17

What does Vx affect?

Answer 17

• 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

Question 18

Fecundity schedules

Answer 18

• 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

Question 19

Fecundity-survivorship trade-offs

Answer 19

cost of reproduction