Topic 12 -Life Histories Flashcards
Allocation decisions, decide where to devote energy
Will affect an individual’s fitness by influencing growth, reproduction and survival
Organisms need to develop allocation strategies over evolutionary time to
Adapt to abiotic and biotic conditions in their environment
Trade off
Increased allocation of time/energy to some activities results in a decreased allocation to other activities
Life history trade off
Growth and survival v.s. Reproduction
Reproductive effort
The proportion of available resources that an individual allocates reproduction throughout its lifespan
Future reproductive output
Survival + fecundity
Fecundity
Number of offspring produced per event
Life time reproductive success
The number of offspring produced throughout the lifespan of an individual
Similar to fitness but does not involve the offspring surviving to reproductive age
Life history strategy
Set of choices and decisions resulting in an individuals allocation to reproductive effort through its life span
Investing in current reproduction
Reduce ability to grow, lower probability of survival
May produce fewer offspring in the future
Investing in current growth/survival
Faster growth, higher probability of survival
Larger size, more resources available for future reproduction
Life history traits (7)
Body size/growth Age at sexual maturity # of reproductive events # of offspring Offspring size Amount of parental care Senescence, programmed death
General pattern for body size/growth
Fecundity increases with body size
Larger individuals have more resources to devote to offspring
General pattern for maturity
Age of maturity increases as adult lifespan or annual survival rate increase
Long lifespan (high annual survival rate)
current fecundity should not jeopardize future growth, survival and reproduction
favour growth in 1st few years to increase fecundity
favour reproduction over lifespan (breed older)
Short lifespan (low annual survival rate)
current fecundity at the expense of adult survival
do not favour growth -may die before breeding
favour current reproduction (breed younger)
general pattern for parity
semelparity occurs more for organisms living under viable environmental conditions
semelparity
reproduce once and die
iteroparity
reproduce repeatedly throughout lifespan
semelparity occurs when
adult survival is low ex mayflies
adult survival is high but long intervals between years when conditions suitable for high offspring survival, organisms will store resources and reproduce when conditions are favourable ex agaves
Fecundity general pattern
As more offspring are produced -the survival of each offspring decrease
the more offspring produced means
fewer resources devoted to those offspring
Oviparous
eggs provided with yolk hatch externally
Ovoviviparous
eggs provided with yolk hatch internally
viviparous
nutrition provided directly by mother, live birth
if resources are abundant
Low competition among individuals in population
Population growth ("intrinsic rate of increase," r) is at its maximumreproduction»>growth/survival
r-selected
large reproduction allocation but invest little in survival
if resources are limited
high competition between individuals of a population
population growth is low -population is at a “carrying capacity,” k.
growth/survival»>reproduction
k-selected
large allocation to survival but little in reproduction
Body size for r and k
r -small
k -large
age of maturity for r and k
r -early
k -late
number of reproductive events for r and k
r -semelparous
k-iteroparous
size of offspring for r and k
r -small
k -large
number of offspring for r and k
r -many
k -few
parental care for r and k
r -low
k -high
