18. Population ecology: age-structured populations and life histories

Question 1

Allee effects

Answer 1

Social benefits such as mate finding, group living, group defense which have negative effects of low density populations

Question 2

Key components of a life history strategy include

Answer 2

1) lifespan
2) timing of reproduction
3) # of offspring
4) parental investment in offspring

Question 3

cost of reproduction =

Answer 3

Fecundity-survivorship trade-offs

Question 4

How to plot survivorship curves

Answer 4

survivorship (lx) vs. Ageclass (x)

Question 5

Type 1 survivorship curve

Answer 5

high survivorship throughout life, majority reaches maturity (humans)

Question 6

Type 2 survivorship curve

Answer 6

constant loss, independent of age (birds, rodents)

Question 7

Type 3 survivorship curve

Answer 7

Early loss, low mortality after maturity (trees)

Question 8

R₀=

Answer 8

average # daughters a female has in her life

Question 9

Constraints and trade-offs

Answer 9

Reproduction is costly. Longer pre-reproductive periods allow time to accumulate more resources

Question 10

Iteroparous

Answer 10

producing offspring multiple years or multiple age classes

Question 11

Semelparous

Answer 11

“big bang” reproducers, produce all reproductive in last year of their lives

Question 12

Advantage of Synchrony

Answer 12

Infrequent pulses of reproduction = predator satiation tacti (If whole population produces seeds at the same time, predators are not able to deplete all resources)

Question 13

Life tables

Answer 13

• Data that summarize the life events that are statistically expected for the average individual of a specified age in a population
  
  • Age of death
  • Age and timing of reproduction
  • For modeling, these are treated as constants
• Usually consider females only

Question 14

K strategy

Answer 14

• Predominates in stable or predictable environments where resources are used for maximising long-term survival
• There are usually very few offspring per brood, each requiring high levels of parental care (resulting in low mortality)
• The body size of offspring is typically larger and they have a late onset of maturity (long developmental span)
• Population size is typically stable (reaches carrying capacity) and an example of K-selection is a climax species

Question 15

r Strategy

Answer 15

• Occurs in unstable environments where there are ecological disruptions and resources are used for maximising reproduction
• There are usually many offspring per brood, which require little parental care and have a high rate of mortality
• The body size of offspring is typically small and they have an early onset of maturity (short developmental span)
• Population size is typically variable (highly fluctuating) and an example of a r-selected organism is a pioneer species