Chapter 7 - Ecology: The Economy of Nature

life history

growth, development, reproduction, longevity

fecundity

number of offspring produced per reproductive episode

parity

number of episodes of reproduction

parental investment

time and energy invested to offspring

principle of allocation

resources are devoted to body function or behavior, they cannot allocate them to another

determinate growth

females do not grow after reproduction (birds and mammals)

indeterminate growth

growth after reproduction (plants, inverts, fish, reptiles, amphibians)

semelparity

one time reproduction

often live in more extreme ecological conditions

iteroparity

reproduce multiple times

annual

1 year lifespan

perennial

more than 1 year lifespan

senescence

decrease in fecundity with increase in probability of mortality

consequence of wear and tear, kind of under genetic control, longer life spans cause slower aging

photoperiod

amount of light that occurs each day

slow-fast continuum

life history traits vary consistently with respect to life form, habitat, and conditions in the environment

variation in one trait is often correlated with other life history trait (slow vs. fast)

combination of life history traits in plants

abiotic stress, competition, and frequency of disturbance

stress tolerators

slow growth, late maturity, low seed energy production, rely on asexual reproduction

competitors

fast growth, early maturity, low seed energy production, sometimes rely on asexual reproduction

ruderals

fast growth, early maturity, high seed energy production, rarely rely on asexual reproduction

what influences life history?

body plan and lifestyle, evolutionary responses to physical conditions, food supply, predators, other biotic factors such as competition

which grows faster? endothermic or ectothermic animals

endothermic

What was Lack’s hypothesis for the differences in life history

the maximum number of offspring that can be reared is limited by food

life history traits influence reproduction and may influence evolutionary fitness

traits vary consistently with environmental factors

Components of fitness

maturity, parity, fecundity, aging

reaction norm

observed relationship between the phenotype and the environment

every 10C adds ___ from 0-32C

18F

genotype by environment interactions are the basis for

specialization

reciprocal transplant experiment

switching of individuals between two localities

common garden experiments

used to determine whether there is genetic difference or phenotypic plasticity

relationship between age and size at metamorphosis is…

the reaction norm of metamorphosis (with respect to age and size)

life histories optimize…

fitness under conflicting demands

O2 in atmosphere

21%

O2 in water

6ppm

rate of change are key for analyzing

the most efficient brood size and adult survival

the age at maturity

varies in direct proportion to lifespan

Per capita growth rate

survivorship plus fecundity times adult survival independent and dependent of reproduction

change in per capita growth rate

survivorship times change in fecundity plus adult survival independent of reproduction times change in adult survival dependent of reproduction

changes in fecundity and adult survival are favored

when net effects on population growth are positive

enhanced fecundity and reduced survival depend on

relationship between survivorship and adult survival

why do some organisms use fecundity over growth?

you’re not going to be here tomorrow so you better get your kids out today

bet hedging

organisms take their chances and produce many offspring in the hope that some of them survive