12: Life History Traits I

reproduction incurs an increased risk of _______

predation

what are the advantages of early reproduction?

increased fecundity, hopefully b4 dying

what are the disadvantages of early reproduction?

decreased survivorship & decreased potential for later reproduction

what are the advantages of later reproduction?

increased growth & survivorship & potential fecundity

what are the disadvantages of later reproduction?

decreased fecundity if death occurs b4 sexual maturity

what is semelparity ?

example?

investing all energy into growth/maintenance, then expend 1 massive reproductive effort b4 dying

Ex// insects, salmon, annual plants, bamboos

what is iteroparity ?

example?

fewer young produced at 1 time, but production of young repeated throughout lifetime

ex// perennial plants, vertebrates, humans

True or false: Its costly to produce too few/ too many offspring OR too small/too large offspring?

TRUE

True or false? Small offspring more likely to survive.

FALSE, large offspring more likely to survive BUT small offspring can be produced in large numbers

what is altricial investment? What does this require?

example?

young are relatively helpless at birth

-requires less gestation time BUT greater parental care

ex// birds & mammals

What is precocial investment?

-what does this require?

examples?

young are relatively independent at birth

-greater gestation time BUT less parental care

ex// gallinaceous birds & ungulate mammals

What are the characteristics of species most likely to produce precocial young?

lacking shelter from predators, thus increasing survivorship of young

annual plant characteristics?

example?

live for less than an year

-unstable, unpredictable environments

-produce an ABUNDANT number of small(windblown) seeds

example// weeds

perennial plants characteristics

example?

live for several or many years

-stable, predictable environments

-produce fewer, bigger seeds

example// nut trees

What is the tradeoff of some perennial plants having fruits?

fruits decrease parental fitness BUT increase offspring fitness

do temperate or tropical species have a larger litter size? Why?

temperate species have larger litter size BC temperate climates are more catastrophic & populations are usually below (K)

do high elevation or low elevation species have a larger litter size?

high elevation species

how is fecundity of plants & poikilotherms related to body size & age?

fecundity increases with size & age

How is age of reproduction related to population density?

example?

Age of 1st reproduction among trees increases as density increases

Ex// Virginia Pine

in open stands→produce seeds at 5-8 yeras

in dense stands→delays seed production up to 50 years

Why do smaller mammals have higher fecundity than large mammals?

higher predation & shorter lifespan requires them to produce more offspring to offset losses

Compare the climate in r-selection vs. K-selection species.

r-selection→harsh, unpredictable climate

K-selection→stable, predictable climate

Compare the Population Growth Rate & Population Density in r-selection vs. K-selection species.

r-selection→high population growth
K-selection→low population growth rate

r-selection→variable & low population density
K-selection→constant & high population density

Compare the Carrying Capacity in r-selection vs. K-selection species.

r-selection→seldom reached
K-selection→near K

Compare the Intraspecific Competition & Development in r-selection vs. K-selection species.

r-selection→low comp. & fast development

K-selection→high comp. & slow development

Compare the Energetics & Reproduction in r-selection vs. K-selection species.

r-selection→productivity & early reproduction, few events

K-selection→ efficiency & late reproduction, repeated events

Compare the body size & life expectancy in r-selection vs. K-selection species.

r-selection→small body size & short life expectancy

K-selection→large body size & long life expectancy

Compare the Survivorship & Mortality in r-selection vs. K-selection species.

r-selection→Type II & III ; density independent mortality
K-selection→ Type I ; density dependent mortality

Names for r-selection?

1) r-strategists

2) opportunists

3) generalists

names for K-selection

1)K-strategists

2) competitors

3) specialists

Examples of r-selection species

1) weeds

2) insects

3) mice

4) songbirds

examples of K-selection species

1) trees

2) eagles

3) elephants

4) humans

are all species ideal r-or K strategists

NO, there is a continuum