Life Histories & Lifetime Reproductive Success Flashcards
What is the life history theory? (LHT)
Provides framework for how animals should allocate time and energy to tasks and traits over lifetime.
This should maximise survival and reproductive fitness
What does the LHT explain?
- why organisms mature early or late
- why organisms have few or many young
- why organisms have short or long life
- vary between species
What does the life history include?
Organisms schedule:
- Birth and growth
- Age of maturity
- Number and size of offspring (fecundity)
- Number of reproductive events (parity)
- Senescence
Define lifetime reproductive success (LRS)
The number of recruits to the following generation the individual produces in a lifetime (estimates individuals fitness)
Combines survival and success into single measure
Determined by life history
More important than reproductive success of a single breeding attempt
What is the slow-fast continuum?
The rate at which events happen in a lifetime. (Fast/slow development, maturity etc)
K selection (slow)
r selection (fast)
What are life histories influenced by?
Natural selection
- vary with environmental factors:
- food supply
- physical conditions
- predation pressures
What do life history traits influence?
Evolutionary fitness
Give an example of the life history fast/slow comtinuum
Bird:
Thrush- matures at 1, produces several broods of 3/4 chicks a year, lives 3/4 years.
Storm petrel- matures at 5, produces a single chick per year, lives 30/40 years.
= different life strategies but same amount of offspring
What are life history trade-offs?
Series of trade-offs in allocating resources. Time, energy and resources devoted to one body system/function can’t be allocated to another
They balance tradeoffs between current and future reproduction
What are the trade offs in age of maturity?
When an animal starts to breed, its generation time is affected.
May benefit animal to start breeding as soon as possible (increase fecundity) BUT if the species is long lived, may be benefits to delaying
What happens when environmental conditions result in reduced adult survival?
Costs of delaying increase risk of mortality with time and reduced fecundity with age
- Selected for early maturation
What are the trade-offs in fecundity?
The more produced in a year, the less parental care it can provide.
Should be optimal within current environmental factors
Increased fecundity in one year reduces growth, this fecundity in future years.
What are the trade offs in parity? What is hypothesised?
Trade off between current and future investments
Hypothesis suggests an animal should be semelparous when prep for reproduction is costly
What does semelparous mean?
‘Big bang reproduction’
- reproduces once before it dies (salmon)
What does iteroparous mean?
Had many reproductive cycles over lifetime (birds, amphibians, mammals and reptiles)
Iteroparity favoured when low current reproduction results in high future reproduction
