Life Histories Flashcards
“Fast” life history/ “r-selected”
Early maturity, short life spans, high number of offspring, little parental investment per offspring. Traits increase population growth. Fruit flies, dandelions “ruderal plants”
“Slow” life history/ “K-selected”
Late maturity, long lifespans, low numbers of offspring, high parental investment per offspring, traits increase competitiveness. elephants, oaktrees
In r and K species, there are correlations between
fecundity and mortality
Life histories depend on … and … factors
extrinsic, intrinsic
Extrinsic factors
Factors operating from the “outside” that affects rates of age-specific reproduction and mortality (environmental influences)
Intrinsic factors
Tradeoffs among traits (phylogeny, physiology, development), genetic constraints.
Principle of Allocation
Trade offs. One resource cannot go to multiple parts of body
Offspring number vs. Parent Care
More offspring, less parental care
Lack’s Hypothesis
Birds should lay the number of eggs yielding the highest number of surviving offspring
Why wouldn’t Lacks hypothesis be there?
other tradeoffs
Determinate Growth
Individual does not grow anymore once it initiates reproduction (birds and mammals)
Indeterminate Growth
An individual continues to grow after initiating reproduction. Plants, invertebrates, fish, reptile
When there is a predator risk, guppies will
have a lot, yet small offspring
Senescence
Gradual decrease in fecundity and increase in the probability of mortality (molecular defect accumulation). High survival rates means stronger selection for delaying senescence. Bats age more slowly than rodents of a similar size
Perennial
Organism that has a lifespan more than one year
