Chapter 8 Flashcards
what do life history traits represent
the schedule of an organism’s life
Life history
the schedule of an organism’s growth, development, reproduction, and survival; represents an allocation of limited time and resources to achieve maximum reproductive success
the schedule of an organism’s growth, development, reproduction, and survival; represents an allocation of limited time and resources to achieve maximum reproductive success
Life history
Fecundity
the number of offspring produced by an organism per reproductive episode
the number of offspring produced by an organism per reproductive episode
Fecundity
Parity
the number of reproductive episodes an organism experiences
the number of reproductive episodes an organism experiences
Parity
Parental investment
the time and energy given to an offspring by its parents
the time and energy given to an offspring by its parents
Parental investment
Longevity (life expectancy)
the life span of an organism.
the life span of an organism.
Longevity (life expectancy)
what do life history traits often vary consistently with
life form, habitat, or environmental conditions
What is variation in one life history trait often correlated with
variation in other life history traits
“slow” life history
- long time to sexual maturity
- long life spans
- low numbers of offspring
- high parental investment
Examples: elephants, oak trees
“fast” life history
- short time to sexual maturity
- short life spans
- high numbers of offspring
- little parental investment
Examples: fruit flies, weeds
short life
r-selected
rapid growth
r-selected
early maturity
r-selected
many small offspring
r-selected
little parental care or protection
r-selected
little investment in individual offspring
r-selected
adapted to unstable environment
r-selected
pioneers, colonizers
r-selected
niche generalists
r-selected
prey
r-selected
regulated mainly by extrinsic factors
r-selected
low trophic level
r-selected
long life
K-selected
slower growth
K-selected
late maturity
K-selected
few, large offspring
K-selected
high parental care or protection
K-selected
high investment in individual offspring
K-selected
adapted to stable environment
K-selected
later stages of succession
K-selected
niche specialists
K-selected
predators
K-selected
regulated mainly by intrinsic factors
K-selected
high trophic level
K-selected
what did J. Philip Grime proprose
plant life history depends on stress, competition, and the frequency of disturbances
stress tolerators
typically small herbs with a long life span, slow growth, and a long time to sexual maturity
what do many stress tolerators rely on
vegetative reproduction (reproducing from roots and stems) instead of producing costly seeds
ruderals
grow fast and devote a high proportion of their energy to reproduction
competitors
when conditions are less stressful, they grow fast, achieve early sexual maturity, and devote little energy to seed production
what are life history traits shaped by
trade-offs
when one life history trait is favored, it…
prevents the adoption of other advantageous traits
Principle of allocation
the observation that when resources are devoted to one body structure, physiological function, or behavior, they cannot be allotted to another
the observation that when resources are devoted to one body structure, physiological function, or behavior, they cannot be allotted to another
Principle of allocation
what will natural selection favor
individuals that allocate their resources in a way that achieves maximum fitness
there is a trade-off between offspring number and…
offspring survival
what does an optimized life history resolve
conflicts between competing demands of survival and reproduction to achieve maximum fitness
most organisms face a trade-off between the number of offspring they can produce and..
the size of those offspring
for many organisms, the number of offspring can be variable, but
the size remains relatively constant
what does selection favor in offspring trade-offs
a uniform offspring size
for many species, it is possible that acquired energy can only be used…
to produce greater offspring numbers
as the number of offspring increases, what decreases
- the amount of parental care per offspring
2. the chances of offspring survival
what does offspring number/parental care depend on
environmental conditions such as the number of daylight hours that parents have to find resources for their offspring
what does having more offspring do
stimulates the parents to hunt harder for food to feed their offspring
- this can affect the parent’s fitness
what does allocation of energy to increased fecundity during one year occur at
the cost of further growth that year
Determinate growth
a growth pattern in which an individual does not grow any more once it initiates reproduction; occurs in many species of birds and mammals
a growth pattern in which an individual does not grow any more once it initiates reproduction; occurs in many species of birds and mammals
Determinate growth
Indeterminate growth
a growth pattern in which an individual continues to grow after it initiates reproduction; occurs in many species of plants, invertebrates, fishes, reptiles, and amphibians
a growth pattern in which an individual continues to grow after it initiates reproduction; occurs in many species of plants, invertebrates, fishes, reptiles, and amphibians
Indeterminate growth
why should organisms with a long life span favor determinate growth
it allows them to grow first and reproduce later
why should organisms with a short life span favor indeterminate growth
it allows them to quickly reproduce before death
what does delaying sexual maturity allow an individual to do
grow large and produce more offspring per year once reproduction begins
comparing across many species, the age of sexual maturity is positively associated with
the number of years an animal will survive after reaching maturity
organisms differ in the number of times that they reproduce, but
they all eventually become senescent
in almost all species, individuals eventually experience a decline in ______ followed by _____.
body condition; death (i.e., senescence)
organisms differ in the number of times they _____ before _____
reproduce; senescence
Semelparity
when organisms reproduce only once during their life; relatively rare in vertebrates, but common in insects and plants
when organisms reproduce only once during their life; relatively rare in vertebrates, but common in insects and plants
Semelparity
Iteroparity
when organisms reproduce multiple times during their life; common among birds, reptiles, mammals, and amphibians
when organisms reproduce multiple times during their life; common among birds, reptiles, mammals, and amphibians
Iteroparity
Annual
an organism that has a life span of one year
an organism that has a life span of one year
Annual
Perennial
an organism that has a life span of more than one year
an organism that has a life span of more than one year
Perennial
when does semelparity arise
when there is a massive amount of energy required for production (ex. bamboos)
it has been repeatedly demonstrated that semelparous species produce more offspring in their fatal reproductive episodes than do
closely related iteroparous species in any one of theirs
Senescence
a gradual decrease in fecundity and an increase in the probability of mortality
a gradual decrease in fecundity and an increase in the probability of mortality
Senescence
an inevitable consequence of natural wear and tear
senescence
might reflect the accumulation of molecular defects that fail to be repaired
senescence
the rate of wear can be modified by
physiological mechanisms that prevent or repair damage
what do long-lived animals appear to have better mechanisms for
reducing the production of reactive forms of oxygen and repairing damaged DNA and protein molecules
What does allocation of resources to these mechanisms depend on
the expected life span of an individual; long-lived individuals should select for better repair mechanisms
what are life histories sensitive to
environmental conditions
why is the right timing of life history events critical
so behavior and physiology match changing environmental conditions
what cues do organisms rely on
various indirect, environmental cues
photoperiod
the amount of light that occurs each day; provides a cue for many events in the life histories of virtually all organisms
the amount of light that occurs each day; provides a cue for many events in the life histories of virtually all organisms
photoperiod
what do fluctuations in resource availability often determine
the timing of life history events
how can predation affect life history traits
time and size at hatching, metamorphosis, sexual maturity
what can have substantial impacts on an organism’s physiological processes
small changes in temperature
what has the increase in global temperature changed of many animals and plants
breeding times
changes in temperature can also alter
the initiation of flower production
