Life historic
The “schedule” of an individual’s life, including age at maturity, number of offspring, life span, number of reproductive opportunities (maturity, fecundity, aging, parity)
On average, all individuals have one offspring that reaches reproduction---from dandelions to house finches to humans
Why must this be the case?
Then why so many different “ways” to achieve the same outcome?
- Basic components of life history:
Maturity: age at 1st reproduction
Parity: number of reproductive episodes/lifetime
Fecundity: number of offspring produced/episode
Life span: survival schedule, aging & senescence
a. Terms:
Semelparity: reproducing only once before programmed death
Iteroparity: reproducing multiple times
For plants specifically, Annual: living one year
Perennial: living >1 year
Examples:
Some species have life histories with high fecundity, short time to maturity, and poor survival (Asian tiger mosquito)
Somewhere in between (Cascades frog)
Some species have life histories with low fecundity, long time to maturity, and high survival (African elephant)
Life history diagrams summarize average life history events (usually involve 1-year time steps)
Life histories are the result of natural selection. They represent successful ways of allocating limited resources to carry out various functions of living organisms.