Chapter 9

Question 1

What are life histories?

Answer 1

• The attributes of the life cycle through which an individual passes, with particular reference to survival and reproduction.
• Expressed through behaviour, physiology, anatomy
• Genetic variation and phenotypic plasticity

Question 2

What are life history traits?

Answer 2

• Age of maturity
• Size at maturity
• Fecundity (#of offspring)
• Size of offspring
• Frequency of reproduction

Question 3

How does the age at maturity varies
across different timescales?

Answer 3

• Minutes (e.g. many bacteria)
• Months (e.g. small mammals)
• Decades (e.g. many sharks, whales)

Question 4

How does maturity and age at
maturity correlate?

Answer 4

Large bodied animals have a later age at maturity

Question 5

What is fecundity?

Answer 5

• Annual fecundity is the number of offspring
  produced by an individual during a breeding season
• Annual fecundity is influenced both by the
  number of reproductive events and the number of offspring per event
• The number of reproductive events
  varies from once in a lifetime to repeatedly
  over centuries (iteroparous vs semelparous)

Question 6

What is the relation between size and # of offspring?

Answer 6

• Across species, there is a negative correlation
  between size and number of offspring.
• Organisms produce numerous small offspring, or few large offspring

Question 7

What is reproductive effort

Answer 7

• Proportion of total energy devoted to reproduction, including:
  – Physiological effort (e.g. energy demands)
  – Anatomical effort (e.g. gonad development)
  – Behavioural effort (e.g. migration)

Question 8

Fecundity and age

Answer 8

In some cases, fecundity is consistent across the lifespan
In others, fecundity increases with female body size (when the female is older)

Question 9

Parental care

Answer 9

• Parental care that follows reproductive events determines how many kids an individual has
• Some organisms (cod) spend lots of energy on # of offspring and none on parental care
  Others have few offspring but lots of parental care (grey seal)

Question 10

Reproductive efforts

Answer 10

• Proportion of total energy devoted to reproducing, including:
  1.) Physiological efforts (energy demand)
  2.) Anatomical efforts (gonad development)
  3.) Behavioural efforts (migration/ finding food)

Question 11

Life history traits vary

Answer 11

Among species
Among populations
Within populations

ex.
Brook trout, Freshwater river:
- Smaller size of maturity
- more eggs
- Larger eggs
- Probably faced with more predators

Brook trout creek
- Focused on semantic growth

Question 12

Constraints

Answer 12

Age at maturity increases with adult body size
Population growth decreses with body size
(small animals reproduce more faster)

Question 13

Bet-hedging strategies

Answer 13

Multiple reproductive events (maybe at different spots)
to assure that at least some of your kids will survive
Increased fitness in suboptimal conditions
Lower in optimal
ex. cod laying eggs over longer intervals because it doesn’t know when it will get the nutrients it needs for it’s ofspring to survive

Question 14

Cost of reproduction

Answer 14

An increase in one life history trait often causes a decrease in another
- Organisms only have so much energy, they can’t maximize everything
ex. Brightest male guppies have the highest reproductive success, but are more visible to predators

Question 15

Selection on life histories

Answer 15

Natural selection favours genotypes where survival and fecundity result in the highest fitness relative to other genotypes
Must survive and reproduce

Question 16

r-selection vs K-selection

Answer 16

r-strtegy= fast reproduction
k-strategy = survival

Question 17

Fast vs slow life histories

Answer 17

Fast (r)
- high fecundity
short life
young age of maturity

Slow (k)
low fecundity
long life

Question 18

Alternative strats

Answer 18

Life history can vary in a species
ex. some animals disguise themselves as females and can mate without having to devote any energy to parental care
- There must be a balance between the two states for it to be effective

Question 19

Harvest can cause evolution

Answer 19

• traits can be altered due to overharvesting
  ex fish size gets smaller to fit through nets