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Life History Theory
This body of theory was developed to explain the diversity of life cycles among living things.
- Two fundamental principles:
- 1. natural selection
- 2. trade offs
- Attempts to identify the various trade offs an organism makes related to growth, survival, and reproduction
- Goal is to understand variation in life cycle strategies
Variation in characteristics reflect different allocation of an individual's resources. Available resources are finite.
- Energy is allocated in 3 seperate ways:
- 1. Growth
- 2. Maintenance & Repain
- 3. Reproduction
- Investment in current offspring- hinders growth and survival and reduces future reproduction.
- Investment in self- increases fecundity and future reproductive potention, but age limited.
RV Reproductive Value
- current and future reproduction
- -when young FR is high
- -when old FR is low
- -shifts trade off to current reproduction
r vs K selection
- Explains selection pressures that determine reproduction strategy
- Central trade off is:
- # of offspring vs timing of reproduction.
- r selected:
- -suited to an unstable environment
- -faster growth rate
- -large number of offspring
- -low parental care
- Most are semelparous (single reproduction/mayflies)
- K selected:
- -suited to life in a stable environment
- -slow growth rate
- -small number of offspring
- -higher parental care
- Most are iteroparous (annual/multiple birthings)
Life History Traits
- -# of offspring
- -juvenile development
- -age sexual maturity
- -age first reproduction
- -parental investment