Bio Ch 9 - Life Histories

Life history

A set of co-evolved traits that affect an individual’s survival and reproductive potential

These traits determine the schedule of an organism’s growth, development, reproduction, and survival

Fecundity

the number of offspring produced by an organism per reproductive episode

Parity

the number of reproductive episodes that an organism experiences

Parental investment

the amount of time and energy given to an offspring by its parents

Longevity

the life span of an organism (life expectancy)

“R-selected” life histories (fast)

shorter life span, faster growth, earlier reproduction and sexual maturation, more offspring, smaller parental investment

“K- selected” life history (slow)

longer life span, slower growth, later sexual maturation and delayed reproduction, fewer offspring and larger parental investment

Stress tolerators (increasing stress)

typically small herbs with a long life span, slow growth, and a long time to sexual maturity. many rely on vegetative reproduction instead of producing seeds (its costly)

Competitors (increasing competition)

grow fast, achieve early sexual maturity, devote little energy to seed production

Ruderals (increasing disturbance)

grow fast and devote a high proportion of their energy to reproduction (seeds)

Complex life cycle

a life history in which an individual lives in different habitats or experiences a substantial change in morphology or physiology

Principle of allocation

when resources are devoted to one body structure, they cannot be allotted to another (there is a trade-off)

Determinate growth

growth pattern in which an individual does not grow after it initiates reproduction (birds and mammals)

organisms with a long life span should favor this because it allows them to continue to grow until they need to reproduce

Indeterminate growth

growth pattern in which an individual continues to grow after initiating reproduction (plants, herps, invertebrates)

organisms with a short life span should favor this because it allows them to reproduce quickly before their life span is over

Semelparity

when organisms reproduce only once during their life- usually occurs when there is a massive amount of energy needed to reproduce

Iteroparity

when an organism reproduces multiple times over its life span

Senescence

the inevitable deterioration that occurs with age

Photoperiod

the amount of light that occurs each day; provides a cue for many events in life histories