Survivorship Curves, Life History Traits, Population Growth Models

per capita rate of increase (r)

birth rate minus death rate per individual positive r means population grown negative r means population decline

density independent

does not depend on the number of individuals

trade off between fecundity and survivorship

either high fecundity or high survivorship, not both

type 2

equal chance of dying at any part of the life cycle song birds, sharks

type 1

ex: humans k selected high survivorship all through life, drops off at the end

k selected

few, larger organisms high energy investment high parental care high survivorship older age of maturity type 1 or 2

cohort

group of individuals of the same age that can be followed in time

logistic growth

involves k, the carrying capacity density dependent delta n/ delta t = rn (k-n/k) more individuals means slower growth

r selected

many, small individuals low chance of surviving early in life low investment per offspring low parental care young age of maturity type 3 curve

type 3

often r selected high mortality early in life, better survivorship later in life ex: frogs

fecundity

producing large amounts of organisms

exponential growth

r is positive and constant density independent delta n/ delta t= r N adds an increasing number of individuals as the population grows happens when there is an abundance of resources, bottleneck, or founder affect ex: human population

density dependent

rate of growth depends on the number of organisms present

carrying capacity (k)

the maximum number of individuals that can be supported and sustained in a particular habitat

intrinsic rate of increase (r max)

the maximum rate of increase of a population based on life history traits optimal conditions for growth species specific r selected often have higher r max value

survivorship:

the proportion of offspring in each cohort that survive to a particular age

life history traits

traits related to how individuals allocate resources to growth, reproduction, or survival have trade offs can't maximize any without sacrificing others